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Date:   Wed, 25 Aug 2021 18:11:48 -0500
From:   Bjorn Andersson <bjorn.andersson@linaro.org>
To:     sbillaka@codeaurora.org
Cc:     Stephen Boyd <swboyd@chromium.org>,
        dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        robdclark@gmail.com, seanpaul@chromium.org,
        kalyan_t@codeaurora.org, abhinavk@codeaurora.org,
        dianders@chromium.org, khsieh@codeaurora.org,
        mkrishn@codeaurora.org
Subject: Re: [PATCH v1 1/2] drm/msm/dp: Add support for SC7280 eDP
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 <0b2aa426c8f511a29143f2a1117fe9a2@codeaurora.org>
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On Thu 12 Aug 19:28 CDT 2021, sbillaka@codeaurora.org wrote:

> On 2021-08-12 06:11, Stephen Boyd wrote:
> > Quoting Sankeerth Billakanti (2021-08-11 17:08:01)
[..]
> > > +static int dp_parser_gpio(struct dp_parser *parser)
> > > +{
> > > +       struct device *dev = &parser->pdev->dev;
> > > +       int ret;
> > > +
> > > +       parser->panel_bklt_gpio = devm_gpiod_get(dev, "panel-bklt",
> > > +                       GPIOD_OUT_HIGH);
> > > +       if (IS_ERR(parser->panel_bklt_gpio)) {
> > > +               ret = PTR_ERR(parser->panel_bklt_gpio);
> > > +               parser->panel_bklt_gpio = NULL;
> > > +               DRM_ERROR("%s: cannot get panel-bklt gpio, %d\n",
> > > __func__, ret);
> > > +               goto fail;
> > > +       }
> > > +
> > > +       parser->panel_pwm_gpio = devm_gpiod_get(dev, "panel-pwm",
> > > GPIOD_OUT_HIGH);
> > > +       if (IS_ERR(parser->panel_pwm_gpio)) {
> > > +               ret = PTR_ERR(parser->panel_pwm_gpio);
> > > +               parser->panel_pwm_gpio = NULL;
> > > +               DRM_ERROR("%s: cannot get panel-pwm gpio, %d\n",
> > > __func__, ret);
> > > +               goto fail;
> > > +       }
> > > +
> > > +       DRM_INFO("gpio on");
> > > +fail:
> > > +       return 0;
> > > +}
> > 
> > Don't we have pwm backlight drivers like
> > drivers/video/backlight/pwm_bl.c to support this? This sort of thing
> > doesn't belong in the dp driver.
> 
> Okay. I will explore it.
> 

I proposed that we attach a drm_panel and allow that to control the
(pwm-)backlight. Here's the link for the DP patch:

https://lore.kernel.org/linux-arm-msm/20210726231351.655302-1-bjorn.andersson@linaro.org/

Regards,
Bjorn