<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/drivers/mailbox, branch v6.15</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>treewide: Switch/rename to timer_delete[_sync]()</title>
<updated>2025-04-05T08:30:12+00:00</updated>
<author>
<name>Thomas Gleixner</name>
<email>tglx@linutronix.de</email>
</author>
<published>2025-04-05T08:17:26+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=8fa7292fee5c5240402371ea89ab285ec856c916'/>
<id>8fa7292fee5c5240402371ea89ab285ec856c916</id>
<content type='text'>
timer_delete[_sync]() replaces del_timer[_sync](). Convert the whole tree
over and remove the historical wrapper inlines.

Conversion was done with coccinelle plus manual fixups where necessary.

Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
timer_delete[_sync]() replaces del_timer[_sync](). Convert the whole tree
over and remove the historical wrapper inlines.

Conversion was done with coccinelle plus manual fixups where necessary.

Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'mailbox-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/jassibrar/mailbox</title>
<updated>2025-03-30T01:25:34+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2025-03-30T01:25:34+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=7f2ff7b6261742ed52aa973ccdf99151b7cc3a50'/>
<id>7f2ff7b6261742ed52aa973ccdf99151b7cc3a50</id>
<content type='text'>
Pull mailbox updates from Jassi Brar:
 "Core:
   - misc rejig of header includes
   - minor const fixes

  Misc:
   - constify amba_id table

  pcc:
   - cleanup and refactoring of shmem and irq handling

  qcom:
   - add MSM8226 compatible

  fsl,mu:
   - add i.MX94 compatible

  mediatek:
   - remove cl in struct cmdq_pkt

  tegra:
   - define dimensioning masks in SoC data"

* tag 'mailbox-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/jassibrar/mailbox: (25 commits)
  mailbox: Remove unneeded semicolon
  mailbox: pcc: Refactor and simplify check_and_ack()
  mailbox: pcc: Always map the shared memory communication address
  mailbox: pcc: Refactor error handling in irq handler into separate function
  mailbox: pcc: Use acpi_os_ioremap() instead of ioremap()
  mailbox: pcc: Return early if no GAS register from pcc_mbox_cmd_complete_check
  mailbox: pcc: Drop unnecessary endianness conversion of pcc_hdr.flags
  mailbox: pcc: Always clear the platform ack interrupt first
  mailbox: pcc: Fix the possible race in updation of chan_in_use flag
  dt-bindings: mailbox: qcom: add compatible for MSM8226 SoC
  dt-bindings: mailbox: fsl,mu: Add i.MX94 compatible
  MAINTAINERS: add mailbox API's tree type and location
  mailbox: remove unused header files
  mailbox: explicitly include &lt;linux/bits.h&gt;
  mailbox: sort headers alphabetically
  mailbox: don't protect of_parse_phandle_with_args with con_mutex
  mailbox: use error ret code of of_parse_phandle_with_args()
  mailbox: arm_mhuv2: Constify amba_id table
  mailbox: arm_mhu_db: Constify amba_id table
  mailbox: arm_mhu: Constify amba_id table
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull mailbox updates from Jassi Brar:
 "Core:
   - misc rejig of header includes
   - minor const fixes

  Misc:
   - constify amba_id table

  pcc:
   - cleanup and refactoring of shmem and irq handling

  qcom:
   - add MSM8226 compatible

  fsl,mu:
   - add i.MX94 compatible

  mediatek:
   - remove cl in struct cmdq_pkt

  tegra:
   - define dimensioning masks in SoC data"

* tag 'mailbox-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/jassibrar/mailbox: (25 commits)
  mailbox: Remove unneeded semicolon
  mailbox: pcc: Refactor and simplify check_and_ack()
  mailbox: pcc: Always map the shared memory communication address
  mailbox: pcc: Refactor error handling in irq handler into separate function
  mailbox: pcc: Use acpi_os_ioremap() instead of ioremap()
  mailbox: pcc: Return early if no GAS register from pcc_mbox_cmd_complete_check
  mailbox: pcc: Drop unnecessary endianness conversion of pcc_hdr.flags
  mailbox: pcc: Always clear the platform ack interrupt first
  mailbox: pcc: Fix the possible race in updation of chan_in_use flag
  dt-bindings: mailbox: qcom: add compatible for MSM8226 SoC
  dt-bindings: mailbox: fsl,mu: Add i.MX94 compatible
  MAINTAINERS: add mailbox API's tree type and location
  mailbox: remove unused header files
  mailbox: explicitly include &lt;linux/bits.h&gt;
  mailbox: sort headers alphabetically
  mailbox: don't protect of_parse_phandle_with_args with con_mutex
  mailbox: use error ret code of of_parse_phandle_with_args()
  mailbox: arm_mhuv2: Constify amba_id table
  mailbox: arm_mhu_db: Constify amba_id table
  mailbox: arm_mhu: Constify amba_id table
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>mailbox: Remove unneeded semicolon</title>
<updated>2025-03-27T01:58:26+00:00</updated>
<author>
<name>Chen Ni</name>
<email>nichen@iscas.ac.cn</email>
</author>
<published>2025-03-10T08:26:28+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=1ec12fd31ecc38e2a81a137be7eec5df51894bcc'/>
<id>1ec12fd31ecc38e2a81a137be7eec5df51894bcc</id>
<content type='text'>
Remove unnecessary semicolons reported by Coccinelle/coccicheck and the
semantic patch at scripts/coccinelle/misc/semicolon.cocci.

Signed-off-by: Chen Ni &lt;nichen@iscas.ac.cn&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Remove unnecessary semicolons reported by Coccinelle/coccicheck and the
semantic patch at scripts/coccinelle/misc/semicolon.cocci.

Signed-off-by: Chen Ni &lt;nichen@iscas.ac.cn&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>mailbox: pcc: Refactor and simplify check_and_ack()</title>
<updated>2025-03-27T01:58:26+00:00</updated>
<author>
<name>Sudeep Holla</name>
<email>sudeep.holla@arm.com</email>
</author>
<published>2025-03-13T15:28:54+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=2475b36401eda70f60e5d18d67ccafb81cedd0f7'/>
<id>2475b36401eda70f60e5d18d67ccafb81cedd0f7</id>
<content type='text'>
The existing check_and_ack() function had unnecessary complexity. The
logic could be streamlined to improve code readability and maintainability.

The command update register needs to be updated in order to acknowledge
the platform notification through type 4 channel. So it can be done
unconditionally. Currently it is complicated just to make use of
pcc_send_data() which also executes the same updation.

In order to simplify, let us just ring the doorbell directly from
check_and_ack() instead of calling into pcc_send_data(). While at it,
rename it into pcc_chan_check_and_ack() to maintain consistency in the
driver.

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The existing check_and_ack() function had unnecessary complexity. The
logic could be streamlined to improve code readability and maintainability.

The command update register needs to be updated in order to acknowledge
the platform notification through type 4 channel. So it can be done
unconditionally. Currently it is complicated just to make use of
pcc_send_data() which also executes the same updation.

In order to simplify, let us just ring the doorbell directly from
check_and_ack() instead of calling into pcc_send_data(). While at it,
rename it into pcc_chan_check_and_ack() to maintain consistency in the
driver.

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>mailbox: pcc: Always map the shared memory communication address</title>
<updated>2025-03-27T01:58:26+00:00</updated>
<author>
<name>Sudeep Holla</name>
<email>sudeep.holla@arm.com</email>
</author>
<published>2025-03-13T15:28:53+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=fa362ffafa51b08cf8e2fcca38e056332f6b9b05'/>
<id>fa362ffafa51b08cf8e2fcca38e056332f6b9b05</id>
<content type='text'>
Currently the shared memory communication address was mapped by the
mailbox client drivers leading to all sorts of inconsistencies.

It also has resulted in the inconsistent attributes used while mapping
the shared memory regions.

In order to remove/eliminate any issues, let us ensures the shared
memory address is always mapped and unmapped when the PCC channels are
requested and release.

We need to map them as the ACPI PCCT associates these shared memory
with each channel subspace and may need use the status or the flags in
the headers of those shared memory communication address regions to
manage the transport/channel.

Note, until all the drivers using PCC start using this mapped shmem,
there might be double mapping of the shared memory address. This
shouldn't have any impact on existing mbox client drivers.

Since there are no users of pcc_chan_ioremap() and also it is mapped
by default, we can stop exporting it and merge the functionality into
pcc_mbox_request_channel().

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Currently the shared memory communication address was mapped by the
mailbox client drivers leading to all sorts of inconsistencies.

It also has resulted in the inconsistent attributes used while mapping
the shared memory regions.

In order to remove/eliminate any issues, let us ensures the shared
memory address is always mapped and unmapped when the PCC channels are
requested and release.

We need to map them as the ACPI PCCT associates these shared memory
with each channel subspace and may need use the status or the flags in
the headers of those shared memory communication address regions to
manage the transport/channel.

Note, until all the drivers using PCC start using this mapped shmem,
there might be double mapping of the shared memory address. This
shouldn't have any impact on existing mbox client drivers.

Since there are no users of pcc_chan_ioremap() and also it is mapped
by default, we can stop exporting it and merge the functionality into
pcc_mbox_request_channel().

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>mailbox: pcc: Refactor error handling in irq handler into separate function</title>
<updated>2025-03-27T01:58:26+00:00</updated>
<author>
<name>Sudeep Holla</name>
<email>sudeep.holla@arm.com</email>
</author>
<published>2025-03-13T15:28:52+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=3a675f50415b95f2ae10bfd932e2154ba1a08ee7'/>
<id>3a675f50415b95f2ae10bfd932e2154ba1a08ee7</id>
<content type='text'>
The existing error handling logic in pcc_mbox_irq() is intermixed with the
main flow of the function. The command complete check and the complete
complete update/acknowledgment are nicely factored into separate functions.

Moves error detection and clearing logic into a separate function called:
pcc_mbox_error_check_and_clear() by extracting error-handling logic from
pcc_mbox_irq().

This ensures error checking and clearing are handled separately and it
improves maintainability by keeping the IRQ handler focused on processing
events.

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The existing error handling logic in pcc_mbox_irq() is intermixed with the
main flow of the function. The command complete check and the complete
complete update/acknowledgment are nicely factored into separate functions.

Moves error detection and clearing logic into a separate function called:
pcc_mbox_error_check_and_clear() by extracting error-handling logic from
pcc_mbox_irq().

This ensures error checking and clearing are handled separately and it
improves maintainability by keeping the IRQ handler focused on processing
events.

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>mailbox: pcc: Use acpi_os_ioremap() instead of ioremap()</title>
<updated>2025-03-27T01:58:26+00:00</updated>
<author>
<name>Sudeep Holla</name>
<email>sudeep.holla@arm.com</email>
</author>
<published>2025-03-13T15:28:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=d181acea5b864e91f38f5771b8961215ce5017ae'/>
<id>d181acea5b864e91f38f5771b8961215ce5017ae</id>
<content type='text'>
The Platform Communication Channel (PCC) mailbox driver currently uses
ioremap() to map channel shared memory regions. However it is preferred
to use acpi_os_ioremap(), which is mapping function specific to EFI/ACPI
defined memory regions. It ensures that the correct memory attributes
are applied when mapping ACPI-provided regions.

While at it, also add checks for handling any errors with the mapping.

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The Platform Communication Channel (PCC) mailbox driver currently uses
ioremap() to map channel shared memory regions. However it is preferred
to use acpi_os_ioremap(), which is mapping function specific to EFI/ACPI
defined memory regions. It ensures that the correct memory attributes
are applied when mapping ACPI-provided regions.

While at it, also add checks for handling any errors with the mapping.

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>mailbox: pcc: Return early if no GAS register from pcc_mbox_cmd_complete_check</title>
<updated>2025-03-27T01:58:25+00:00</updated>
<author>
<name>Sudeep Holla</name>
<email>sudeep.holla@arm.com</email>
</author>
<published>2025-03-13T15:28:50+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=4119a44c71840e6ab9a8d340ca09e7b3210ade76'/>
<id>4119a44c71840e6ab9a8d340ca09e7b3210ade76</id>
<content type='text'>
pcc_mbox_cmd_complete_check() accesses pchan-&gt;cmd_complete.gas to check
command completion status. Even if GAS is NULL, pcc_chan_reg_read() gets
called which returns success doing nothing and then we return.

Add an early return if pchan-&gt;cmd_complete.gas == NULL before performing
any operations.

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
pcc_mbox_cmd_complete_check() accesses pchan-&gt;cmd_complete.gas to check
command completion status. Even if GAS is NULL, pcc_chan_reg_read() gets
called which returns success doing nothing and then we return.

Add an early return if pchan-&gt;cmd_complete.gas == NULL before performing
any operations.

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>mailbox: pcc: Drop unnecessary endianness conversion of pcc_hdr.flags</title>
<updated>2025-03-27T01:58:25+00:00</updated>
<author>
<name>Sudeep Holla</name>
<email>sudeep.holla@arm.com</email>
</author>
<published>2025-03-13T15:28:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=29237e6df42b08ccb4152121ec2c650fdae103e1'/>
<id>29237e6df42b08ccb4152121ec2c650fdae103e1</id>
<content type='text'>
The Sparse static checker flags a type mismatch warning related to
endianness conversion:

  |  warning: incorrect type in argument 1 (different base types)
  |     expected restricted __le32 const [usertype] *p
  |     got unsigned int *

This is because an explicit endianness conversion (le32_to_cpu()) was
applied unnecessarily to a pcc_hdr.flags field that is already in
little-endian format.

The PCC driver is only enabled on little-endian kernels due to its
dependency on ACPI and EFI, making the explicit conversion unnecessary.

The redundant conversion occurs in pcc_chan_check_and_ack() for the
pcc_hdr.flags field. Drop this unnecessary endianness conversion of
pcc_hdr.flags.

Also drop the redundant PCC_ACK_FLAG_MASK definition and use the
more appropriate and already defined PCC_CMD_COMPLETION_NOTIFY.

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The Sparse static checker flags a type mismatch warning related to
endianness conversion:

  |  warning: incorrect type in argument 1 (different base types)
  |     expected restricted __le32 const [usertype] *p
  |     got unsigned int *

This is because an explicit endianness conversion (le32_to_cpu()) was
applied unnecessarily to a pcc_hdr.flags field that is already in
little-endian format.

The PCC driver is only enabled on little-endian kernels due to its
dependency on ACPI and EFI, making the explicit conversion unnecessary.

The redundant conversion occurs in pcc_chan_check_and_ack() for the
pcc_hdr.flags field. Drop this unnecessary endianness conversion of
pcc_hdr.flags.

Also drop the redundant PCC_ACK_FLAG_MASK definition and use the
more appropriate and already defined PCC_CMD_COMPLETION_NOTIFY.

Acked-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>mailbox: pcc: Always clear the platform ack interrupt first</title>
<updated>2025-03-27T01:58:25+00:00</updated>
<author>
<name>Sudeep Holla</name>
<email>sudeep.holla@arm.com</email>
</author>
<published>2025-03-13T15:28:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=cf1338c0e02880cd235a4590eeb15e2039c873bc'/>
<id>cf1338c0e02880cd235a4590eeb15e2039c873bc</id>
<content type='text'>
The PCC mailbox interrupt handler (pcc_mbox_irq()) currently checks
for command completion flags and any error status before clearing the
interrupt.

The below sequence highlights an issue in the handling of PCC mailbox
interrupts, specifically when dealing with doorbell notifications and
acknowledgment between the OSPM and the platform where type3 and type4
channels are sharing the interrupt.

-------------------------------------------------------------------------
| T |       Platform Firmware         |    OSPM/Linux PCC driver        |
|---|---------------------------------|---------------------------------|
| 1 |                                 | Build message in shmem          |
| 2 |                                 | Ring Type3 chan doorbell        |
| 3 | Receives the doorbell interrupt |                                 |
| 4 | Process the message from OSPM   |                                 |
| 5 | Build response for the message  |                                 |
| 6 | Ring Platform ACK interrupt on  |                                 |
|   |  Type3 chan to OSPM             | Received the interrupt          |
| 7 | Build Notification in Type4 Chan|                                 |
| 8 |                                 | Start processing interrupt in   |
|   |                                 |  pcc_mbox_irq() handler         |
| 9 |                                 | Enter PCC handler for Type4 chan|
|10 |                                 | Check command complete cleared  |
|11 |                                 | Read the notification           |
|12 |                                 | Clear Platform ACK interrupt    |
|   | No effect from the previous step yet as the Platform ACK          |
|   |  interrupt has not yet been triggered for this channel            |
|13 | Ring Platform ACK interrupt on  |                                 |
|   | Type4 chan to OSPM              |                                 |
|14 |                                 | Enter PCC handler for Type3 chan|
|15 |                                 | Command complete is set.        |
|16 |                                 | Read the response.              |
|17 |                                 | Clear Platform ACK interrupt    |
|18 |                                 | Leave PCC handler for Type3     |
|19 |                                 | Leave pcc_mbox_irq() handler    |
|20 |                                 | Re-enter pcc_mbox_irq() handler |
|21 |                                 | Enter PCC handler for Type4 chan|
|22 |                                 | Leave PCC handler for Type4 chan|
|23 |                                 | Enter PCC handler for Type3 chan|
|24 |                                 | Leave PCC handler for Type3 chan|
|25 |                                 | Leave pcc_mbox_irq() handler    |
-------------------------------------------------------------------------

The key issue occurs when OSPM tries to acknowledge platform ack
interrupt for a notification which is ready to be read and processed
but the interrupt itself is not yet triggered by the platform.

This ineffective acknowledgment leads to an issue later in time where
the interrupt remains pending as we exit the interrupt handler without
clearing the platform ack interrupt as there is no pending response or
notification. The interrupt acknowledgment order is incorrect.

To resolve this issue, the platform acknowledgment interrupt should
always be cleared before processing the interrupt for any notifications
or response.

Reported-by: Robbie King &lt;robbiek@xsightlabs.com&gt;
Reviewed-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Tested-by: Robbie King &lt;robbiek@xsightlabs.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The PCC mailbox interrupt handler (pcc_mbox_irq()) currently checks
for command completion flags and any error status before clearing the
interrupt.

The below sequence highlights an issue in the handling of PCC mailbox
interrupts, specifically when dealing with doorbell notifications and
acknowledgment between the OSPM and the platform where type3 and type4
channels are sharing the interrupt.

-------------------------------------------------------------------------
| T |       Platform Firmware         |    OSPM/Linux PCC driver        |
|---|---------------------------------|---------------------------------|
| 1 |                                 | Build message in shmem          |
| 2 |                                 | Ring Type3 chan doorbell        |
| 3 | Receives the doorbell interrupt |                                 |
| 4 | Process the message from OSPM   |                                 |
| 5 | Build response for the message  |                                 |
| 6 | Ring Platform ACK interrupt on  |                                 |
|   |  Type3 chan to OSPM             | Received the interrupt          |
| 7 | Build Notification in Type4 Chan|                                 |
| 8 |                                 | Start processing interrupt in   |
|   |                                 |  pcc_mbox_irq() handler         |
| 9 |                                 | Enter PCC handler for Type4 chan|
|10 |                                 | Check command complete cleared  |
|11 |                                 | Read the notification           |
|12 |                                 | Clear Platform ACK interrupt    |
|   | No effect from the previous step yet as the Platform ACK          |
|   |  interrupt has not yet been triggered for this channel            |
|13 | Ring Platform ACK interrupt on  |                                 |
|   | Type4 chan to OSPM              |                                 |
|14 |                                 | Enter PCC handler for Type3 chan|
|15 |                                 | Command complete is set.        |
|16 |                                 | Read the response.              |
|17 |                                 | Clear Platform ACK interrupt    |
|18 |                                 | Leave PCC handler for Type3     |
|19 |                                 | Leave pcc_mbox_irq() handler    |
|20 |                                 | Re-enter pcc_mbox_irq() handler |
|21 |                                 | Enter PCC handler for Type4 chan|
|22 |                                 | Leave PCC handler for Type4 chan|
|23 |                                 | Enter PCC handler for Type3 chan|
|24 |                                 | Leave PCC handler for Type3 chan|
|25 |                                 | Leave pcc_mbox_irq() handler    |
-------------------------------------------------------------------------

The key issue occurs when OSPM tries to acknowledge platform ack
interrupt for a notification which is ready to be read and processed
but the interrupt itself is not yet triggered by the platform.

This ineffective acknowledgment leads to an issue later in time where
the interrupt remains pending as we exit the interrupt handler without
clearing the platform ack interrupt as there is no pending response or
notification. The interrupt acknowledgment order is incorrect.

To resolve this issue, the platform acknowledgment interrupt should
always be cleared before processing the interrupt for any notifications
or response.

Reported-by: Robbie King &lt;robbiek@xsightlabs.com&gt;
Reviewed-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Huisong Li &lt;lihuisong@huawei.com&gt;
Tested-by: Adam Young &lt;admiyo@os.amperecomputing.com&gt;
Tested-by: Robbie King &lt;robbiek@xsightlabs.com&gt;
Signed-off-by: Sudeep Holla &lt;sudeep.holla@arm.com&gt;
Signed-off-by: Jassi Brar &lt;jassisinghbrar@gmail.com&gt;
</pre>
</div>
</content>
</entry>
</feed>
