<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/arch/mips, branch v4.4.253</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>MIPS: BCM47XX: fix kconfig dependency bug for BCM47XX_BCMA</title>
<updated>2020-12-29T12:42:35+00:00</updated>
<author>
<name>Necip Fazil Yildiran</name>
<email>fazilyildiran@gmail.com</email>
</author>
<published>2020-11-02T21:34:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=334eeb468709801de68447f4b1326ab777d8142b'/>
<id>334eeb468709801de68447f4b1326ab777d8142b</id>
<content type='text'>
[ Upstream commit 3a5fe2fb9635c43359c9729352f45044f3c8df6b ]

When BCM47XX_BCMA is enabled and BCMA_DRIVER_PCI is disabled, it results
in the following Kbuild warning:

WARNING: unmet direct dependencies detected for BCMA_DRIVER_PCI_HOSTMODE
  Depends on [n]: MIPS [=y] &amp;&amp; BCMA_DRIVER_PCI [=n] &amp;&amp; PCI_DRIVERS_LEGACY [=y] &amp;&amp; BCMA [=y]=y
  Selected by [y]:
  - BCM47XX_BCMA [=y] &amp;&amp; BCM47XX [=y] &amp;&amp; PCI [=y]

The reason is that BCM47XX_BCMA selects BCMA_DRIVER_PCI_HOSTMODE without
depending on or selecting BCMA_DRIVER_PCI while BCMA_DRIVER_PCI_HOSTMODE
depends on BCMA_DRIVER_PCI. This can also fail building the kernel.

Honor the kconfig dependency to remove unmet direct dependency warnings
and avoid any potential build failures.

Fixes: c1d1c5d4213e ("bcm47xx: add support for bcma bus")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=209879
Signed-off-by: Necip Fazil Yildiran &lt;fazilyildiran@gmail.com&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 3a5fe2fb9635c43359c9729352f45044f3c8df6b ]

When BCM47XX_BCMA is enabled and BCMA_DRIVER_PCI is disabled, it results
in the following Kbuild warning:

WARNING: unmet direct dependencies detected for BCMA_DRIVER_PCI_HOSTMODE
  Depends on [n]: MIPS [=y] &amp;&amp; BCMA_DRIVER_PCI [=n] &amp;&amp; PCI_DRIVERS_LEGACY [=y] &amp;&amp; BCMA [=y]=y
  Selected by [y]:
  - BCM47XX_BCMA [=y] &amp;&amp; BCM47XX [=y] &amp;&amp; PCI [=y]

The reason is that BCM47XX_BCMA selects BCMA_DRIVER_PCI_HOSTMODE without
depending on or selecting BCMA_DRIVER_PCI while BCMA_DRIVER_PCI_HOSTMODE
depends on BCMA_DRIVER_PCI. This can also fail building the kernel.

Honor the kconfig dependency to remove unmet direct dependency warnings
and avoid any potential build failures.

Fixes: c1d1c5d4213e ("bcm47xx: add support for bcma bus")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=209879
Signed-off-by: Necip Fazil Yildiran &lt;fazilyildiran@gmail.com&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>MIPS: Alchemy: Fix memleak in alchemy_clk_setup_cpu</title>
<updated>2020-11-24T11:48:11+00:00</updated>
<author>
<name>Zhang Qilong</name>
<email>zhangqilong3@huawei.com</email>
</author>
<published>2020-11-13T13:18:56+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=354c6294a6393830ce7527ba33c48d88e30d3c52'/>
<id>354c6294a6393830ce7527ba33c48d88e30d3c52</id>
<content type='text'>
[ Upstream commit ac3b57adf87ad9bac7e33ca26bbbb13fae1ed62b ]

If the clk_register fails, we should free h before
function returns to prevent memleak.

Fixes: 474402291a0ad ("MIPS: Alchemy: clock framework integration of onchip clocks")
Reported-by: Hulk Robot &lt;hulkci@huawei.com&gt;
Signed-off-by: Zhang Qilong &lt;zhangqilong3@huawei.com&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit ac3b57adf87ad9bac7e33ca26bbbb13fae1ed62b ]

If the clk_register fails, we should free h before
function returns to prevent memleak.

Fixes: 474402291a0ad ("MIPS: Alchemy: clock framework integration of onchip clocks")
Reported-by: Hulk Robot &lt;hulkci@huawei.com&gt;
Signed-off-by: Zhang Qilong &lt;zhangqilong3@huawei.com&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>MIPS: Fix BUILD_ROLLBACK_PROLOGUE for microMIPS</title>
<updated>2020-11-24T11:48:11+00:00</updated>
<author>
<name>Paul Burton</name>
<email>paul.burton@imgtec.com</email>
</author>
<published>2016-08-19T17:15:40+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=622b0c1f679dc6e1b9ac2006a7c542f9a51b963e'/>
<id>622b0c1f679dc6e1b9ac2006a7c542f9a51b963e</id>
<content type='text'>
[ Upstream commit 1eefcbc89cf3a8e252e5aeb25825594699b47360 ]

When the kernel is built for microMIPS, branches targets need to be
known to be microMIPS code in order to result in bit 0 of the PC being
set. The branch target in the BUILD_ROLLBACK_PROLOGUE macro was simply
the end of the macro, which may be pointing at padding rather than at
code. This results in recent enough GNU linkers complaining like so:

    mips-img-linux-gnu-ld: arch/mips/built-in.o: .text+0x3e3c: Unsupported branch between ISA modes.
    mips-img-linux-gnu-ld: final link failed: Bad value
    Makefile:936: recipe for target 'vmlinux' failed
    make: *** [vmlinux] Error 1

Fix this by changing the branch target to be the start of the
appropriate handler, skipping over any padding.

Signed-off-by: Paul Burton &lt;paul.burton@imgtec.com&gt;
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14019/
Signed-off-by: Ralf Baechle &lt;ralf@linux-mips.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 1eefcbc89cf3a8e252e5aeb25825594699b47360 ]

When the kernel is built for microMIPS, branches targets need to be
known to be microMIPS code in order to result in bit 0 of the PC being
set. The branch target in the BUILD_ROLLBACK_PROLOGUE macro was simply
the end of the macro, which may be pointing at padding rather than at
code. This results in recent enough GNU linkers complaining like so:

    mips-img-linux-gnu-ld: arch/mips/built-in.o: .text+0x3e3c: Unsupported branch between ISA modes.
    mips-img-linux-gnu-ld: final link failed: Bad value
    Makefile:936: recipe for target 'vmlinux' failed
    make: *** [vmlinux] Error 1

Fix this by changing the branch target to be the start of the
appropriate handler, skipping over any padding.

Signed-off-by: Paul Burton &lt;paul.burton@imgtec.com&gt;
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14019/
Signed-off-by: Ralf Baechle &lt;ralf@linux-mips.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>MIPS: Add the missing 'CPU_1074K' into __get_cpu_type()</title>
<updated>2020-10-01T09:11:57+00:00</updated>
<author>
<name>Wei Li</name>
<email>liwei391@huawei.com</email>
</author>
<published>2020-09-23T06:53:12+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=ad692d58dae16b6286e293231ccf3186cd019253'/>
<id>ad692d58dae16b6286e293231ccf3186cd019253</id>
<content type='text'>
[ Upstream commit e393fbe6fa27af23f78df6e16a8fd2963578a8c4 ]

Commit 442e14a2c55e ("MIPS: Add 1074K CPU support explicitly.") split
1074K from the 74K as an unique CPU type, while it missed to add the
'CPU_1074K' in __get_cpu_type(). So let's add it back.

Fixes: 442e14a2c55e ("MIPS: Add 1074K CPU support explicitly.")
Signed-off-by: Wei Li &lt;liwei391@huawei.com&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit e393fbe6fa27af23f78df6e16a8fd2963578a8c4 ]

Commit 442e14a2c55e ("MIPS: Add 1074K CPU support explicitly.") split
1074K from the 74K as an unique CPU type, while it missed to add the
'CPU_1074K' in __get_cpu_type(). So let's add it back.

Fixes: 442e14a2c55e ("MIPS: Add 1074K CPU support explicitly.")
Signed-off-by: Wei Li &lt;liwei391@huawei.com&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>MIPS: SNI: Fix spurious interrupts</title>
<updated>2020-09-23T06:44:27+00:00</updated>
<author>
<name>Thomas Bogendoerfer</name>
<email>tsbogend@alpha.franken.de</email>
</author>
<published>2020-09-16T13:54:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=16783098e0c1ffdf0015645bd7602abca23c4fb4'/>
<id>16783098e0c1ffdf0015645bd7602abca23c4fb4</id>
<content type='text'>
[ Upstream commit b959b97860d0fee8c8f6a3e641d3c2ad76eab6be ]

On A20R machines the interrupt pending bits in cause register need to be
updated by requesting the chipset to do it. This needs to be done to
find the interrupt cause and after interrupt service. In
commit 0b888c7f3a03 ("MIPS: SNI: Convert to new irq_chip functions") the
function to do after service update got lost, which caused spurious
interrupts.

Fixes: 0b888c7f3a03 ("MIPS: SNI: Convert to new irq_chip functions")
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit b959b97860d0fee8c8f6a3e641d3c2ad76eab6be ]

On A20R machines the interrupt pending bits in cause register need to be
updated by requesting the chipset to do it. This needs to be done to
find the interrupt cause and after interrupt service. In
commit 0b888c7f3a03 ("MIPS: SNI: Convert to new irq_chip functions") the
function to do after service update got lost, which caused spurious
interrupts.

Fixes: 0b888c7f3a03 ("MIPS: SNI: Convert to new irq_chip functions")
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>MIPS: SNI: Fix MIPS_L1_CACHE_SHIFT</title>
<updated>2020-09-23T06:44:27+00:00</updated>
<author>
<name>Thomas Bogendoerfer</name>
<email>tsbogend@alpha.franken.de</email>
</author>
<published>2020-09-14T16:05:00+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=5c56e5fc60b501877437281b84f8ddcf7241e5f2'/>
<id>5c56e5fc60b501877437281b84f8ddcf7241e5f2</id>
<content type='text'>
[ Upstream commit 564c836fd945a94b5dd46597d6b7adb464092650 ]

Commit 930beb5ac09a ("MIPS: introduce MIPS_L1_CACHE_SHIFT_&lt;N&gt;") forgot
to select the correct MIPS_L1_CACHE_SHIFT for SNI RM. This breaks non
coherent DMA because of a wrong allocation alignment.

Fixes: 930beb5ac09a ("MIPS: introduce MIPS_L1_CACHE_SHIFT_&lt;N&gt;")
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 564c836fd945a94b5dd46597d6b7adb464092650 ]

Commit 930beb5ac09a ("MIPS: introduce MIPS_L1_CACHE_SHIFT_&lt;N&gt;") forgot
to select the correct MIPS_L1_CACHE_SHIFT for SNI RM. This breaks non
coherent DMA because of a wrong allocation alignment.

Fixes: 930beb5ac09a ("MIPS: introduce MIPS_L1_CACHE_SHIFT_&lt;N&gt;")
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>mips/vdso: Fix resource leaks in genvdso.c</title>
<updated>2020-09-03T09:19:24+00:00</updated>
<author>
<name>Peng Fan</name>
<email>fanpeng@loongson.cn</email>
</author>
<published>2020-07-14T12:30:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=a43f5de749e72a960003264833dab4407af00fbd'/>
<id>a43f5de749e72a960003264833dab4407af00fbd</id>
<content type='text'>
[ Upstream commit a859647b4e6bfeb192284d27d24b6a0c914cae1d ]

Close "fd" before the return of map_vdso() and close "out_file"
in main().

Signed-off-by: Peng Fan &lt;fanpeng@loongson.cn&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit a859647b4e6bfeb192284d27d24b6a0c914cae1d ]

Close "fd" before the return of map_vdso() and close "out_file"
in main().

Signed-off-by: Peng Fan &lt;fanpeng@loongson.cn&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>MIPS: CPU#0 is not hotpluggable</title>
<updated>2020-08-21T08:53:05+00:00</updated>
<author>
<name>Huacai Chen</name>
<email>chenhc@lemote.com</email>
</author>
<published>2020-07-16T10:40:23+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=e8f18159737d57154d7947eb936fa9fc51a95de2'/>
<id>e8f18159737d57154d7947eb936fa9fc51a95de2</id>
<content type='text'>
commit 9cce844abf07b683cff5f0273977d5f8d0af94c7 upstream.

Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices
/system/cpu/cpu0/online which confuses some user-space tools.

Cc: stable@vger.kernel.org
Signed-off-by: Huacai Chen &lt;chenhc@lemote.com&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 9cce844abf07b683cff5f0273977d5f8d0af94c7 upstream.

Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices
/system/cpu/cpu0/online which confuses some user-space tools.

Cc: stable@vger.kernel.org
Signed-off-by: Huacai Chen &lt;chenhc@lemote.com&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>MIPS: Fix build for LTS kernel caused by backporting lpj adjustment</title>
<updated>2020-07-22T07:10:07+00:00</updated>
<author>
<name>Huacai Chen</name>
<email>chenhc@lemote.com</email>
</author>
<published>2020-07-16T09:39:29+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=13c5c64880c563319ab45f2192ca20eeeeb3ebca'/>
<id>13c5c64880c563319ab45f2192ca20eeeeb3ebca</id>
<content type='text'>
Commit ed26aacfb5f71eecb20a ("mips: Add udelay lpj numbers adjustment")
has backported to 4.4~5.4, but the "struct cpufreq_freqs" (and also the
cpufreq notifier machanism) of 4.4~4.19 are different from the upstream
kernel. These differences cause build errors, and this patch can fix the
build.

Cc: Serge Semin &lt;Sergey.Semin@baikalelectronics.ru&gt;
Cc: Stable &lt;stable@vger.kernel.org&gt; # 4.4/4.9/4.14/4.19
Signed-off-by: Huacai Chen &lt;chenhc@lemote.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Commit ed26aacfb5f71eecb20a ("mips: Add udelay lpj numbers adjustment")
has backported to 4.4~5.4, but the "struct cpufreq_freqs" (and also the
cpufreq notifier machanism) of 4.4~4.19 are different from the upstream
kernel. These differences cause build errors, and this patch can fix the
build.

Cc: Serge Semin &lt;Sergey.Semin@baikalelectronics.ru&gt;
Cc: Stable &lt;stable@vger.kernel.org&gt; # 4.4/4.9/4.14/4.19
Signed-off-by: Huacai Chen &lt;chenhc@lemote.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>MIPS: Add missing EHB in mtc0 -&gt; mfc0 sequence for DSPen</title>
<updated>2020-07-09T07:35:09+00:00</updated>
<author>
<name>Hauke Mehrtens</name>
<email>hauke@hauke-m.de</email>
</author>
<published>2020-07-02T22:53:34+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=7d04fcf7d3c7028a1f6e4f6837d109a03e31405c'/>
<id>7d04fcf7d3c7028a1f6e4f6837d109a03e31405c</id>
<content type='text'>
commit fcec538ef8cca0ad0b84432235dccd9059c8e6f8 upstream.

This resolves the hazard between the mtc0 in the change_c0_status() and
the mfc0 in configure_exception_vector(). Without resolving this hazard
configure_exception_vector() could read an old value and would restore
this old value again. This would revert the changes change_c0_status()
did. I checked this by printing out the read_c0_status() at the end of
per_cpu_trap_init() and the ST0_MX is not set without this patch.

The hazard is documented in the MIPS Architecture Reference Manual Vol.
III: MIPS32/microMIPS32 Privileged Resource Architecture (MD00088), rev
6.03 table 8.1 which includes:

   Producer | Consumer | Hazard
  ----------|----------|----------------------------
   mtc0     | mfc0     | any coprocessor 0 register

I saw this hazard on an Atheros AR9344 rev 2 SoC with a MIPS 74Kc CPU.
There the change_c0_status() function would activate the DSPen by
setting ST0_MX in the c0_status register. This was reverted and then the
system got a DSP exception when the DSP registers were saved in
save_dsp() in the first process switch. The crash looks like this:

[    0.089999] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.097796] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.107070] Kernel panic - not syncing: Unexpected DSP exception
[    0.113470] Rebooting in 1 seconds..

We saw this problem in OpenWrt only on the MIPS 74Kc based Atheros SoCs,
not on the 24Kc based SoCs. We only saw it with kernel 5.4 not with
kernel 4.19, in addition we had to use GCC 8.4 or 9.X, with GCC 8.3 it
did not happen.

In the kernel I bisected this problem to commit 9012d011660e ("compiler:
allow all arches to enable CONFIG_OPTIMIZE_INLINING"), but when this was
reverted it also happened after commit 172dcd935c34b ("MIPS: Always
allocate exception vector for MIPSr2+").

Commit 0b24cae4d535 ("MIPS: Add missing EHB in mtc0 -&gt; mfc0 sequence.")
does similar changes to a different file. I am not sure if there are
more places affected by this problem.

Signed-off-by: Hauke Mehrtens &lt;hauke@hauke-m.de&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit fcec538ef8cca0ad0b84432235dccd9059c8e6f8 upstream.

This resolves the hazard between the mtc0 in the change_c0_status() and
the mfc0 in configure_exception_vector(). Without resolving this hazard
configure_exception_vector() could read an old value and would restore
this old value again. This would revert the changes change_c0_status()
did. I checked this by printing out the read_c0_status() at the end of
per_cpu_trap_init() and the ST0_MX is not set without this patch.

The hazard is documented in the MIPS Architecture Reference Manual Vol.
III: MIPS32/microMIPS32 Privileged Resource Architecture (MD00088), rev
6.03 table 8.1 which includes:

   Producer | Consumer | Hazard
  ----------|----------|----------------------------
   mtc0     | mfc0     | any coprocessor 0 register

I saw this hazard on an Atheros AR9344 rev 2 SoC with a MIPS 74Kc CPU.
There the change_c0_status() function would activate the DSPen by
setting ST0_MX in the c0_status register. This was reverted and then the
system got a DSP exception when the DSP registers were saved in
save_dsp() in the first process switch. The crash looks like this:

[    0.089999] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.097796] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.107070] Kernel panic - not syncing: Unexpected DSP exception
[    0.113470] Rebooting in 1 seconds..

We saw this problem in OpenWrt only on the MIPS 74Kc based Atheros SoCs,
not on the 24Kc based SoCs. We only saw it with kernel 5.4 not with
kernel 4.19, in addition we had to use GCC 8.4 or 9.X, with GCC 8.3 it
did not happen.

In the kernel I bisected this problem to commit 9012d011660e ("compiler:
allow all arches to enable CONFIG_OPTIMIZE_INLINING"), but when this was
reverted it also happened after commit 172dcd935c34b ("MIPS: Always
allocate exception vector for MIPSr2+").

Commit 0b24cae4d535 ("MIPS: Add missing EHB in mtc0 -&gt; mfc0 sequence.")
does similar changes to a different file. I am not sure if there are
more places affected by this problem.

Signed-off-by: Hauke Mehrtens &lt;hauke@hauke-m.de&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

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