linux.git/drivers/tty/serial/msm_serial.c, branch v4.7

tty: serial: msm: Support more bauds

2016-04-30T16:26:55+00:00

The msm_find_best_baud() function is written with the assumption
that the port->uartclk rate is fixed to a particular rate at boot
time, but now this driver changes that clk rate at runtime when
the baud is changed.

The way the hardware works is that an input clk rate comes from
the clk controller into the uart hw block. That rate is typically
1843200 or 3686400 Hz. That rate can then be divided by an
internal divider in the hw block to achieve a particular baud on
the serial wire. msm_find_best_baud() is looking for that divider
value.

A few things are wrong with the way the code is written. First,
it assumes that the maximum baud that the uart can support if the
clk rate is fixed at boot is 460800, which would correspond to an
input clk rate of 230400 * 16 == 3686400 Hz.  Except some devices
have a boot rate of 1843200 Hz or max baud of 115200, so
achieving 230400 on those devices doesn't work at all because we
don't increase the clk rate unless max baud is 460800.

Second, we can't achieve bauds higher than 460800 that require
anything besides a divisor of 1, because we always call
msm_find_best_baud() with a fixed port->uartclk rate that will
eventually be changed after we calculate the divisor. So if we
need to get a baud of 500000, we'll just multiply that by 16 and
hope that the clk can give us 500000 * 16 == 8000000 Hz, which it
typically can't do. To really achieve 500000 baud, we need to get
an input clk rate of 24000000 Hz and then divide that by 3 inside
the uart hardware.

Finally, we return success for bauds even when we can't actually
achieve them. This means that when the user asks for 500000 baud,
we actually get 921600 right now, but the user doesn't know that.

Fix all of this by searching through the divisor and clk rate
space with a combination of clk_round_rate() and baud
calculations, keeping track of the best clk rate and divisor we
find if we can't get an exact match. Typically we can get an
exact match with a divisor of 1, but sometimes we need to keep
track and try more frequencies. On my msm8916 device, this
results in all standard bauds in baud_table being supported
except for 1800, 576000, 1152000, and 4000000.

Fixes: 850b37a71bde ("tty: serial: msm: Remove 115.2 Kbps maximum baud rate limitation")
Cc: "Ivan T. Ivanov" 
Cc: Matthew McClintock 
Signed-off-by: Stephen Boyd 
Tested-by: Srinivas Kandagatla 
Acked-by: Andy Gross 
Acked-by: Bjorn Andersson 
Tested-by: Cristian Prundeanu 
Signed-off-by: Greg Kroah-Hartman

tty: msm_serial: remove static clk rate setting in probe

2016-04-30T16:26:55+00:00

The issue with setting up a fixed clock rate at probe is that it would
overwrite the console rate set by the bootloader for its console device.
This would result in serial out corruption or missing log when we system
is booted with earlycon. This is not a issue if we boot system without
earlycon.

This setup is at least not required with the mainline driver, this code
used to be required because the clk_enable() call would fail if
clk_set_rate() wasn't called first.

Originally the issue was noticed on DB410c which is based on APQ8016
chipset.

Without this patch the console log with earlycon would look like:
...
[    0.000000] RCU: Adjusting geometry for rcu_fanout_leaf=64, nr_cpu_ids=1
[    0.000000] NR_IRQS:64 nr_irqs:64 0
����+HH��0.699378] console [ttyMSM0] enabled
[    0.699378] console [ttyMSM0] enabled
[    0.702003] bootconsole [uart0] disabled
[    0.702003] bootconsole [uart0] disabled
...

with this patch I can see all the skipped lines on the console

Reviewed-by: Stephen Boyd 
Signed-off-by: Srinivas Kandagatla 
Acked-by: Andy Gross 
Tested-by: Pramod Gurav 
Signed-off-by: Greg Kroah-Hartman

earlycon: Use common framework for earlycon declarations

2016-02-07T06:07:37+00:00

Use a single common table of struct earlycon_id for both command line
and devicetree. Re-define OF_EARLYCON_DECLARE() macro to instance a
unique earlycon declaration (the declaration is only guaranteed to be
unique within a compilation unit; separate compilation units must still
use unique earlycon names).

The semantics of OF_EARLYCON_DECLARE() is different; it declares an
earlycon which can matched either on the command line or by devicetree.
EARLYCON_DECLARE() is semantically unchanged; it declares an earlycon
which is matched by command line only. Remove redundant instances of
EARLYCON_DECLARE().

This enables all earlycons to properly initialize struct console
with the appropriate name and index, which improves diagnostics and
enables direct earlycon-to-console handoff.

Acked-by: Rob Herring 
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: serial: msm: Remove 115.2 Kbps maximum baud rate limitation

2015-10-04T18:15:17+00:00

UART controller is capable to perform transfers up to 4 Mbps.
Remove artificial 115.2 Kbps limitation.

Signed-off-by: Ivan T. Ivanov 
Signed-off-by: Greg Kroah-Hartman

tty: serial: msm: Add RX DMA support

2015-10-04T18:15:17+00:00

Add receive DMA support for UARTDM type of controllers.

Tested on APQ8064, which have UARTDM v1.3 and ADM DMA engine
and APQ8016, which have UARTDM v1.4 and BAM DMA engine.

Signed-off-by: Ivan T. Ivanov 
Signed-off-by: Greg Kroah-Hartman

tty: serial: msm: Add TX DMA support

2015-10-04T18:15:17+00:00

Add transmit DMA support for UARTDM type of controllers.

Tested on APQ8064, which have UARTDM v1.3 and ADM DMA engine
and APQ8016, which have UARTDM v1.4 and BAM DMA engine.

Signed-off-by: Ivan T. Ivanov 
Signed-off-by: Greg Kroah-Hartman

tty: serial: msm: Add msm prefix to all driver functions

2015-10-04T18:15:17+00:00

Make function naming consistent across this driver.
Also rename msm_irq to msm_uart_irq. No functional changes.

Signed-off-by: Ivan T. Ivanov 
Reviewed-by: Stephen Boyd 
Signed-off-by: Greg Kroah-Hartman

tty: serial: msm: Add mask value for UART_DM registers

2015-10-04T18:15:17+00:00

The bit masks for RFR_LEVEL1 and STALE_TIMEOUT_MSB values in MR1 and
IPR registers respectively are different for UART and UART_DM hardware
cores. We have been using UART core mask values for these. Add the same
for UART_DM core.

There is no bit setting as UART_IPR_RXSTALE_LAST for UART_DM core so do
it only for UART core.

Signed-off-by: Pramod Gurav 
Reviewed-by: Stephen Boyd 
Signed-off-by: Ivan T. Ivanov 
Signed-off-by: Greg Kroah-Hartman

tty: serial: msm_serial: Remove console unregistration from driver exit.

2015-02-02T18:11:25+00:00

unregister_console() will be called from uart_remove_one_port() while
removing the platform driver. So not necessary to call it in driver
exit path.

Signed-off-by: Pramod Gurav 
Reviewed-by: Stephen Boyd 
Signed-off-by: Greg Kroah-Hartman

tty: serial: msm_serial: code cleanup in msm_console_setup

2015-02-02T18:11:25+00:00

The change does following:
 - baud, flow, bits, parity were being overwritten as they were
   being reinitialized after parsing.  Initialize them when they are
   declared so that user provided setting are not overwritten.
 - msm_set_baud_rate() is anyway called in uart_set_options when it calls
   msm_set_termios(). msm_reset() is called when we change the baud rate.
   Hence doing away with both of these calls.
 - CR_CMD_PROTECTION_EN and CR_TX_ENABLE settings are done in msm_set_baud_rate.
   So do away with this here.

Signed-off-by: Pramod Gurav 
Reviewed-by: Stephen Boyd 
Signed-off-by: Greg Kroah-Hartman