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    SubjectRe: [PATCH] atmel_lcdfb: suspend/resume support
    On Thu, 13 Mar 2008 11:19:37 -0800
    David Brownell <david-b@pacbell.net> wrote:

    > On Thursday 13 March 2008, Haavard Skinnemoen wrote:
    >
    > > > + sinfo->saved_lcdcon = lcdc_readl(sinfo, ATMEL_LCDC_CONTRAST_VAL);
    > >
    > > You're saving CONTRAST_VAL into a field called saved_lcdcon even though
    > > it has nothing to do with LCDCON1 or LCDCON2...
    >
    > Yeah, why don't registers named LCDCONx have nothing
    > to do with LCD CONtrast? Better to have named the PWM
    > registers PWM ... and say they could be used for either
    > contrast or backlight control.

    While I admit you have a point, I think it's easier to change the name
    of that field than changing the hardware documentation at this point ;)

    > The saved contrast/backlight counter value CONTRAST_VAL is
    > one of two PWM control registers.

    I know.

    > > > + lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR, 0);
    > >
    > > ...then you're altering CONTRAST_CTR...
    >
    > That's forces the contrast signal low and disables the
    > PWM counter, so it won't "randomly" leave the PWM output
    > high when the clock is stopped (leaving at least some
    > displays lit during suspend).

    I'm not saying it's the wrong thing to do. I just think it's strange
    that you alter a different register than the one you saved.

    > It's possible that only CTR needed to be saved; all the
    > backlight support in this driver still needs work.

    Yes, I do think we can assume VAL stays unchanged during suspend.

    > > > +}
    > > > +
    > > > +static int atmel_lcdfb_resume(struct platform_device *pdev)
    > > > +{
    > >
    > > > + lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR, sinfo->saved_lcdcon);
    > >
    > > ...and later restoring the saved value of CONTRAST_VAL into CONTRAST_CTR.
    > >
    > > Confused.
    >
    > Yeah, that looks wrong; the patch below makes more sense.
    > Though it *does* behave right for some reason...

    Yes, that looks better. Perhaps you used a contrast value that happened
    to set the right bits when written to CTR?

    I still think the name of the saved_lcdcon field is confusing though.

    Haavard


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