Re: [PATCH] backlight: l4f00242t03: Fix reset sequence

From: Alberto Panizzo
Date: Tue Jan 04 2011 - 19:33:13 EST


On Tue, 2011-01-04 at 15:59 -0800, Andrew Morton wrote:
> On Sun, 28 Nov 2010 18:13:53 +0100
> Alberto Panizzo <maramaopercheseimorto@xxxxxxxxx> wrote:
>
> > The reset command is part of the init sequence and it take effect
> > only if the lcd is powered.
> >
> > Signed-off-by: Alberto Panizzo <maramaopercheseimorto@xxxxxxxxx>
> > ---
> >
> > This patch is built on top of:
> > http://userweb.kernel.org/~akpm/mmotm/broken-out/drivers-video-backlight-l4f00242t03c-full-implement-fb-power-states-for-this-lcd.patch
> >
> > drivers/video/backlight/l4f00242t03.c | 3 ++-
> > 1 files changed, 2 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/video/backlight/l4f00242t03.c b/drivers/video/backlight/l4f00242t03.c
> > index 5d25743..c04aa90 100644
> > --- a/drivers/video/backlight/l4f00242t03.c
> > +++ b/drivers/video/backlight/l4f00242t03.c
> > @@ -62,6 +62,8 @@ static void l4f00242t03_lcd_init(struct spi_device *spi)
> > regulator_enable(priv->core_reg);
> > }
> >
> > + l4f00242t03_reset(pdata->reset_gpio);
> > +
> > gpio_set_value(pdata->data_enable_gpio, 1);
> > msleep(60);
> > spi_write(spi, (const u8 *)cmd, ARRAY_SIZE(cmd) * sizeof(u16));
> > @@ -225,7 +227,6 @@ static int __devinit l4f00242t03_probe(struct spi_device *spi)
> > }
> >
> > /* Init the LCD */
> > - l4f00242t03_reset(pdata->reset_gpio);
> > l4f00242t03_lcd_init(spi);
> > priv->lcd_state = FB_BLANK_VSYNC_SUSPEND;
> > l4f00242t03_lcd_power_set(priv->ld, FB_BLANK_UNBLANK);
>
> What were the user-visible effects of the bug which you just fixed?
>
> Please always include this info when sending a bugfix! Because without
> that info it's much harder to work out whether we should backport the
> fix into earlier kernels and it's harder for end-users and distro
> maintainers to work out if the patch will fix particular behaviour
> which they or their customers are seeing.
>

The effect of the bug was that the sequence:
set lcd power_state to FB_BLANK_POWERDOWN
set lcd power_state to FB_BLANK_UNBLANK
Did not produced a complete reboot of the LCD which was showing fuzzy
colours.

This was not experienced before implementing correctly all the LCD power
states with the patch [1]. Since before the patch [1] the regulators
were not touched and the LCD shutdown was reached with a register
write. After the patch [1] a complete boot sequence with an initial
reset is needed for the display every time the LCD is powered up.

drivers-video-backlight-l4f00242t03c-full-implement-fb-power-states-for-this-lcd.patch

Best Regards,
--
Alberto!

Be Persistent!
- Greg Kroah-Hartman (FOSDEM 2010)

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