[PATCH] backlight: corgi_lcd: Use gpio_set_value_cansleep() for akita machines to avoid WARN_ON trigger

Tue Dec 4 17:28:24 EST 2012

On Fri, Nov 30, 2012 at 7:16 AM, Jingoo Han <jg1.han at samsung.com> wrote:
> On Friday, November 30, 2012 10:06 AM, Marko Katic wrote
>>
>> From: Marko Katic <dromede.gmail.com>
>>
>> Changing backlight intensity on an Akita (Sharp Zaurus C-1000)
>> will always trigger a WARN_ON:
>>
>> WARNING: at drivers/gpio/gpiolib.c:1672 __gpio_set_value+0x38/0xa4()
>> Modules linked in:
>> Backtrace:
>> [<c000c0ac>] (dump_backtrace+0x0/0x110) from [<c02c8278>] (dump_stack+0x18/0x1c)
>>  r6:c0158fc8 r5:00000009 r4:00000000 r3:c03d4f70
>> [<c02c8260>] (dump_stack+0x0/0x1c) from [<c0019194>] (warn_slowpath_common+0x54/0x6c)
>> [<c0019140>] (warn_slowpath_common+0x0/0x6c) from [<c00191d0>] (warn_slowpath_null+0x24/0x2c)
>>  r8:c38d5c00 r7:c03f82c0 r6:00000000 r5:000000d0 r4:c384e4fc
>> r3:00000009
>> [<c00191ac>] (warn_slowpath_null+0x0/0x2c) from [<c0158fc8>] (__gpio_set_value+0x38/0xa4)
>> [<c0158f90>] (__gpio_set_value+0x0/0xa4) from [<c0169b4c>] (corgi_bl_set_intensity+0x44/0x74)
>>  r7:c3933418 r6:c3933400 r5:c392cdf0 r4:0000002f
>> [<c0169b08>] (corgi_bl_set_intensity+0x0/0x74) from [<c0169c1c>] (corgi_bl_update_status+0x5c/0x64)
>>  r5:c03d31f0 r4:c3933400
>> [<c0169bc0>] (corgi_bl_update_status+0x0/0x64) from [<c02c3a68>] (corgi_lcd_probe+0x1a8/0x258)
>>  r4:c392cdf0 r3:c0169bc0
>> [<c02c38c0>] (corgi_lcd_probe+0x0/0x258) from [<c01da7a4>] (spi_drv_probe+0x20/0x24)
>>  r8:00000052 r7:c0192d9c r6:c03da6e8 r5:c38d5c34 r4:c38d5c00
>> [<c01da784>] (spi_drv_probe+0x0/0x24) from [<c0192c44>] (driver_probe_device+0xb0/0x208)
>> [<c0192b94>] (driver_probe_device+0x0/0x208) from [<c0192e0c>] (__driver_attach+0x70/0x94)
>>  r6:c03da6e8 r5:c38d5c34 r4:c38d5c00 r3:00000000
>> [<c0192d9c>] (__driver_attach+0x0/0x94) from [<c0191268>] (bus_for_each_dev+0x54/0x90)
>>  r6:c03da6e8 r5:c3827e80 r4:00000000 r3:00000000
>> [<c0191214>] (bus_for_each_dev+0x0/0x90) from [<c01927a4>] (driver_attach+0x20/0x28)
>>  r7:00000000 r6:c03e29ec r5:c3932980 r4:c03da6e8
>> [<c0192784>] (driver_attach+0x0/0x28) from [<c0192340>] (bus_add_driver+0xd4/0x22c)
>> [<c019226c>] (bus_add_driver+0x0/0x22c) from [<c019335c>] (driver_register+0xa4/0x134)
>>  r8:00000052 r7:c03ea900 r6:c03c32ac r5:c03bdfc8 r4:c03da6e8
>> [<c01932b8>] (driver_register+0x0/0x134) from [<c01db7ec>] (spi_register_driver+0x4c/0x60)
>> [<c01db7a0>] (spi_register_driver+0x0/0x60) from [<c03b3ce0>] (corgi_lcd_driver_init+0x14/0x1c)
>> [<c03b3ccc>] (corgi_lcd_driver_init+0x0/0x1c) from [<c000868c>] (do_one_initcall+0x9c/0x174)
>> [<c00085f0>] (do_one_initcall+0x0/0x174) from [<c02c1b94>] (kernel_init+0xf4/0x2a8)
>> [<c02c1aa0>] (kernel_init+0x0/0x2a8) from [<c0009270>] (ret_from_fork+0x14/0x24)
>> ---[ end trace a863a63f242ee38c ]---
>>
>> Akita machines have backlight controls hooked to a gpio expander chip, max7310.
>> The driver that controls the max7310 sets the cansleep flag and the corgi_lcd
>> driver only uses plain gpio_set_value calls for changing backlight controls.
>> This triggers the WARN_ON on akita machines.
>>
>> Akita is the only exception in this case since other users of corgi_bl access
>> backlight gpio controls through a different gpio expander which does not set the cansleep flag.
>
> How about modifying the commit message as below?
>
> Akita machines have backlight controls hooked to a gpio expander chip,
> max7310. In this case, pca953x_gpio_set_value() can be called to control
> gpio, and pca953x_setup_gpio() sets can_sleep flag. Therefore,
> gpio_set_value_cansleep() should be used in order to avoid WARN_ON on
> akita machines.
>
Ok, i'll be more specific in my v2 commit message.
> Akita is the only exception in this case since other users of corgi_lcd
> access backlight gpio controls through a different gpio expander which
> does not set the can_sleep flag.
>
>>
>> Fix this by conditionally using gpio_set_value_cansleep() when changing backlight intensity on
>> akita machines.
>
> I don't think this sentence is necessary.

Fine by me.

>
>>
>> Signed-off-by: Marko Katic <dromede at gmail.com>
>> ---
>>  drivers/video/backlight/corgi_lcd.c |   18 +++++++++++++-----
>>  1 file changed, 13 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/video/backlight/corgi_lcd.c b/drivers/video/backlight/corgi_lcd.c
>> index c781768..f33e26f 100644
>> --- a/drivers/video/backlight/corgi_lcd.c
>> +++ b/drivers/video/backlight/corgi_lcd.c
>> @@ -26,7 +26,7 @@
>>  #include <linux/spi/corgi_lcd.h>
>>  #include <linux/slab.h>
>>  #include <asm/mach/sharpsl_param.h>
>> -
>> +#include <asm/mach-types.h>
>>  #define POWER_IS_ON(pwr)     ((pwr) <= FB_BLANK_NORMAL)
>>
>>  /* Register Addresses */
>> @@ -408,11 +408,19 @@ static int corgi_bl_set_intensity(struct corgi_lcd *lcd, int intensity)
>>       /* Bit 5 via GPIO_BACKLIGHT_CONT */
>>       cont = !!(intensity & 0x20) ^ lcd->gpio_backlight_cont_inverted;
>>
>> -     if (gpio_is_valid(lcd->gpio_backlight_cont))
>> -             gpio_set_value(lcd->gpio_backlight_cont, cont);
>> +     if (gpio_is_valid(lcd->gpio_backlight_cont)) {
>> +             if (machine_is_akita())
>> +                     gpio_set_value_cansleep(lcd->gpio_backlight_cont, cont);
>> +             else
>> +                     gpio_set_value(lcd->gpio_backlight_cont, cont);
>> +     }
>
> Please don't use machine-specific code such as machine_is_akita().
> Using machine_is_xxx() in drivers is not preferable.
> gpio_cansleep() would be better.
>
> However, there seems to be no difference between gpio_set_value_cansleep()
> and gpio_set_value(), except for WARN_ON(chip->can_sleep);
> So, if there is no side effect at other machines, please use only
> gpio_set_value_cansleep().
>

I'm not in favor of this approach. Differences between these
functions might be small now but that might change sometime
in the future. I thinks akpm's solution is good.

>
> Best regards,
> Jingoo Han
>
>>
>> -     if (gpio_is_valid(lcd->gpio_backlight_on))
>> -             gpio_set_value(lcd->gpio_backlight_on, intensity);
>> +     if (gpio_is_valid(lcd->gpio_backlight_on)) {
>> +             if (machine_is_akita())
>> +                     gpio_set_value_cansleep(lcd->gpio_backlight_on, intensity);
>> +             else
>> +                     gpio_set_value(lcd->gpio_backlight_on, intensity);
>> +     }
>>
>>       if (lcd->kick_battery)
>>               lcd->kick_battery();
>> --
>> 1.7.10.4
>