linux-kernel - Re: [PATCH v3] backlight: corgi_lcd: Use gpio_set_value_cansleep() to avoid WARN

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Message-id: <000001cdd27f$a88f1000$f9ad3000$%han@samsung.com>
Date:	Wed, 05 Dec 2012 09:29:59 +0900
From:	Jingoo Han <jg1.han@...sung.com>
To:	'Marko Katić' <dromede@...il.com>
Cc:	'Andrew Morton' <akpm@...ux-foundation.org>,
	'LKML' <linux-kernel@...r.kernel.org>,
	'Grant Likely' <grant.likely@...retlab.ca>,
	'Florian Tobias Schandinat' <FlorianSchandinat@....de>,
	'Richard Purdie' <rpurdie@...ys.net>,
	linux-arm-kernel@...ts.infradead.org,
	'Jingoo Han' <jg1.han@...sung.com>
Subject: Re: [PATCH v3] backlight: corgi_lcd: Use gpio_set_value_cansleep() to
 avoid WARN_ON

On Wednesday, December 05, 2012 8:28 AM, Marko Katic wrote
> On Tue, Dec 4, 2012 at 6:28 AM, Jingoo Han <jg1.han@...sung.com> wrote:
> > From: Marko Katic <dromede@...il.com>
> >
> > Changing backlight intensity on an Akita (Sharp Zaurus C-1000)
> > triggers WARN_ON message:
> >
> > 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. 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.
> >
> > Akita is the only exception in this case since other users of corgi_lcd
> > access backlight gpio controls through a different gpio expander such as
> > max7310 which does not set the can_sleep flag.
> 
> I think you forgot to delete "such as max7310". Akita has
> the max7310, all the other models have a different expander.

Yes, you're right.
I added an unnecessary word, 'such as max7310'.
It should be deleted.

I will send v4 patch, soon.

Best regards,
Jingoo Han

> 
> >
> > [jg1.han@...sung.com: used gpio_cansleep()]
> > Signed-off-by: Marko Katic <dromede@...il.com>
> > Signed-off-by: Jingoo Han <jg1.han@...sung.com>
> > ---
> >  drivers/video/backlight/corgi_lcd.c |   17 +++++++++++++----
> >  1 files changed, 13 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/video/backlight/corgi_lcd.c b/drivers/video/backlight/corgi_lcd.c
> > index e2e1b62..e5168f4 100644
> > --- a/drivers/video/backlight/corgi_lcd.c
> > +++ b/drivers/video/backlight/corgi_lcd.c
> > @@ -408,11 +408,20 @@ 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 (gpio_cansleep(lcd->gpio_backlight_cont))
> > +                       gpio_set_value_cansleep(lcd->gpio_backlight_cont, cont);
> > +               else
> > +                       gpio_set_value(lcd->gpio_backlight_cont, cont);
> > +       }
> >
> > -       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 (gpio_cansleep(lcd->gpio_backlight_on))
> > +                       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();
> > --
> > 1.7.2.5
> >
> >

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