Re: [PATCH] fbdev: atmel_lcdfb: Rework backlight status updates
On Fri, 10 Jun 2022 10:49:55 +0100, Daniel Thompson wrote: > On Thu, Jun 09, 2022 at 07:45:11PM +0200, Stephen Kitt wrote: > > Hi Sam, Daniel, > > > > On Thu, 9 Jun 2022 19:30:57 +0200, Sam Ravnborg wrote: > > > > > thanks for taking care of all these backlight simplifications - this > > > really helps to make the code simpler and more readable. > > > > You’re welcome! I noticed fb_blank was deprecated and near enough unused, > > and started digging... > > I saw Sam's comment and kinda wished I'd thought to say that... definitely > good to see these things being tidied up. Thanks! I saw the nice wrapper functions in backlight.h and couldn’t resist. Regards, Stephen pgpL3_7dQWXRH.pgp Description: OpenPGP digital signature
Re: [PATCH] fbdev: atmel_lcdfb: Rework backlight status updates
On Thu, Jun 09, 2022 at 07:45:11PM +0200, Stephen Kitt wrote: > Hi Sam, Daniel, > > On Thu, 9 Jun 2022 19:30:57 +0200, Sam Ravnborg wrote: > > thanks for taking care of all these backlight simplifications - this > > really helps to make the code simpler and more readable. > > You’re welcome! I noticed fb_blank was deprecated and near enough unused, and > started digging... I saw Sam's comment and kinda wished I'd thought to say that... definitely good to see these things being tidied up. Daniel.
Re: [PATCH] fbdev: atmel_lcdfb: Rework backlight status updates
Hi Sam, Daniel, On Thu, 9 Jun 2022 19:30:57 +0200, Sam Ravnborg wrote: > thanks for taking care of all these backlight simplifications - this > really helps to make the code simpler and more readable. You’re welcome! I noticed fb_blank was deprecated and near enough unused, and started digging... > On Thu, Jun 09, 2022 at 10:54:12AM +0100, Daniel Thompson wrote: > > On Wed, Jun 08, 2022 at 10:56:23PM +0200, Stephen Kitt wrote: > > > Instead of checking the state of various backlight_properties fields > > > against the memorised state in atmel_lcdfb_info.bl_power, > > > atmel_bl_update_status() should retrieve the desired state using > > > backlight_get_brightness (which takes into account the power state, > > > blanking etc.). This means the explicit checks using props.fb_blank > > > and props.power can be dropped. > > > > > > Then brightness can only be negative if the backlight is on but > > > props.brightness is negative, so the test before reading the > > > brightness value from the hardware can be simplified to > > > (brightness < 0). > > > > props.brightness should always be in the interval 0..max_brightness. > > > > This is enforced by the main backlight code (and APIs to set the > > brightness use unsigned values). Thus props.brightness could only be > > negative is the driver explicitly sets a negative value as some kind of > > placeholder (which this driver does not do). > > > > I don't think there is any need to keep this logic. > > Daniel is right - please drop the "if (brightness < 0)" logic. > I have looked a bit on the datasheet in my attempt to do a drm version > of this driver - something that I am yet to succeed and the backlight > core avoid any negative values. Thanks for the reviews! I’ve prepared a v2 without the (brightness < 0) logic, I’m about to submit it. Regards, Stephen pgprkzPSpGJXf.pgp Description: OpenPGP digital signature
Re: [PATCH] fbdev: atmel_lcdfb: Rework backlight status updates
Hi Stephen, thanks for taking care of all these backlight simplifications - this really helps to make the code simpler and more readable. On Thu, Jun 09, 2022 at 10:54:12AM +0100, Daniel Thompson wrote: > On Wed, Jun 08, 2022 at 10:56:23PM +0200, Stephen Kitt wrote: > > Instead of checking the state of various backlight_properties fields > > against the memorised state in atmel_lcdfb_info.bl_power, > > atmel_bl_update_status() should retrieve the desired state using > > backlight_get_brightness (which takes into account the power state, > > blanking etc.). This means the explicit checks using props.fb_blank > > and props.power can be dropped. > > > > Then brightness can only be negative if the backlight is on but > > props.brightness is negative, so the test before reading the > > brightness value from the hardware can be simplified to > > (brightness < 0). > > props.brightness should always be in the interval 0..max_brightness. > > This is enforced by the main backlight code (and APIs to set the > brightness use unsigned values). Thus props.brightness could only be > negative is the driver explicitly sets a negative value as some kind of > placeholder (which this driver does not do). > > I don't think there is any need to keep this logic. Daniel is right - please drop the "if (brightness < 0)" logic. I have looked a bit on the datasheet in my attempt to do a drm version of this driver - something that I am yet to succeed and the backlight core avoid any negative values. Sam
Re: [PATCH] fbdev: atmel_lcdfb: Rework backlight status updates
On Wed, Jun 08, 2022 at 10:56:23PM +0200, Stephen Kitt wrote:
> Instead of checking the state of various backlight_properties fields
> against the memorised state in atmel_lcdfb_info.bl_power,
> atmel_bl_update_status() should retrieve the desired state using
> backlight_get_brightness (which takes into account the power state,
> blanking etc.). This means the explicit checks using props.fb_blank
> and props.power can be dropped.
>
> Then brightness can only be negative if the backlight is on but
> props.brightness is negative, so the test before reading the
> brightness value from the hardware can be simplified to
> (brightness < 0).
props.brightness should always be in the interval 0..max_brightness.
This is enforced by the main backlight code (and APIs to set the
brightness use unsigned values). Thus props.brightness could only be
negative is the driver explicitly sets a negative value as some kind of
placeholder (which this driver does not do).
I don't think there is any need to keep this logic.
Daniel.
> diff --git a/drivers/video/fbdev/atmel_lcdfb.c
> b/drivers/video/fbdev/atmel_lcdfb.c
> index 1fc8de4ecbeb..06159a4da293 100644
> --- a/drivers/video/fbdev/atmel_lcdfb.c
> +++ b/drivers/video/fbdev/atmel_lcdfb.c
> @@ -109,22 +108,10 @@ static u32 contrast_ctr = ATMEL_LCDC_PS_DIV8
> static int atmel_bl_update_status(struct backlight_device *bl)
> {
> struct atmel_lcdfb_info *sinfo = bl_get_data(bl);
> - int power = sinfo->bl_power;
> - int brightness = bl->props.brightness;
> + int brightness = backlight_get_brightness(bl);
>
> - /* REVISIT there may be a meaningful difference between
> - * fb_blank and power ... there seem to be some cases
> - * this doesn't handle correctly.
> - */
> - if (bl->props.fb_blank != sinfo->bl_power)
> - power = bl->props.fb_blank;
> - else if (bl->props.power != sinfo->bl_power)
> - power = bl->props.power;
> -
> - if (brightness < 0 && power == FB_BLANK_UNBLANK)
> + if (brightness < 0)
> brightness = lcdc_readl(sinfo, ATMEL_LCDC_CONTRAST_VAL);
> - else if (power != FB_BLANK_UNBLANK)
> - brightness = 0;
>
> lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_VAL, brightness);
> if (contrast_ctr & ATMEL_LCDC_POL_POSITIVE)
