linux-kernel - Re: [RFC][PATCH 1/3] drm/bridge: adv7511: Rework adv7511_power_on/off() so they can be reused internally

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Message-ID: <1926540.Y3AOuWnbYN@avalon>
Date:   Tue, 22 Nov 2016 10:27:42 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        David Airlie <airlied@...ux.ie>,
        Archit Taneja <architt@...eaurora.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [RFC][PATCH 1/3] drm/bridge: adv7511: Rework adv7511_power_on/off() so they can be reused internally

Hi John,

On Tuesday 22 Nov 2016 00:16:55 John Stultz wrote:
> On Tue, Nov 22, 2016 at 12:14 AM, Laurent Pinchart wrote:
> > On Monday 21 Nov 2016 16:37:30 John Stultz wrote:
> >> In chasing down issues with EDID probing, I found some
> >> duplicated but incomplete logic used to power the chip on and
> >> off.
> >> 
> >> This patch refactors the adv7511_power_on/off functions, so
> >> they can be used for internal needs, and replaces duplicative
> >> logic that powers the chip on and off around the EDID probing
> >> with the common logic.
> >> 
> >> Cc: David Airlie <airlied@...ux.ie>
> >> Cc: Archit Taneja <architt@...eaurora.org>
> >> Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>
> >> Cc: Lars-Peter Clausen <lars@...afoo.de>
> >> Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> >> Cc: dri-devel@...ts.freedesktop.org
> >> Signed-off-by: John Stultz <john.stultz@...aro.org>
> >> ---
> >> 
> >>  drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 30 +++++++++-------------
> >>  1 file changed, 14 insertions(+), 16 deletions(-)
> >> 
> >> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> >> b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c index 8dba729..b240e05
> >> 100644
> >> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> >> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> >> @@ -325,7 +325,7 @@ static void adv7511_set_link_config(struct adv7511
> >> *adv7511, adv7511->rgb = config->input_colorspace == HDMI_COLORSPACE_RGB;
> >> 
> >>  }
> >> 
> >> -static void adv7511_power_on(struct adv7511 *adv7511)
> >> +static void __adv7511_power_on(struct adv7511 *adv7511)
> >>  {
> >>       adv7511->current_edid_segment = -1;
> >> 
> >> @@ -343,6 +343,7 @@ static void adv7511_power_on(struct adv7511 *adv7511)
> >>                            ADV7511_INT1_DDC_ERROR);
> >>       }
> >> 
> >> +
> > 
> > This isn't needed.
> 
> Apologies. I saw this right after I sent it!
> 
> >>       /*
> >>        * Per spec it is allowed to pulse the HPD signal to indicate that
> >>        the
> >>        * EDID information has changed. Some monitors do this when they
> >> wakeup
> >> @@ -362,11 +363,15 @@ static void adv7511_power_on(struct adv7511
> >> *adv7511)
> >> 
> >>       if (adv7511->type == ADV7533)
> >>               adv7533_dsi_power_on(adv7511);
> >> +}
> >> 
> >> +static void adv7511_power_on(struct adv7511 *adv7511)
> >> +{
> >> +     __adv7511_power_on(adv7511);
> >>       adv7511->powered = true;
> >>  }
> >> 
> >> -static void adv7511_power_off(struct adv7511 *adv7511)
> >> +static void __adv7511_power_off(struct adv7511 *adv7511)
> >>  {
> >>       /* TODO: setup additional power down modes */
> >>       regmap_update_bits(adv7511->regmap, ADV7511_REG_POWER,
> >> @@ -376,7 +381,11 @@ static void adv7511_power_off(struct adv7511
> >> *adv7511)
> >> 
> >>       if (adv7511->type == ADV7533)
> >>               adv7533_dsi_power_off(adv7511);
> >> +}
> >> 
> >> +static void adv7511_power_off(struct adv7511 *adv7511)
> >> +{
> >> +     __adv7511_power_off(adv7511);
> >>       adv7511->powered = false;
> >>  }
> >> 
> >> @@ -545,24 +554,13 @@ static int adv7511_get_modes(struct adv7511
> >> *adv7511,
> >>       unsigned int count;
> >>       
> >>       /* Reading the EDID only works if the device is powered */
> >> -     if (!adv7511->powered) {
> >> -             regmap_update_bits(adv7511->regmap, ADV7511_REG_POWER,
> >> -                                ADV7511_POWER_POWER_DOWN, 0);
> >> -             if (adv7511->i2c_main->irq) {
> >> -                     regmap_write(adv7511->regmap,
> > 
> > ADV7511_REG_INT_ENABLE(0),
> > 
> >> -                                  ADV7511_INT0_EDID_READY);
> >> -                     regmap_write(adv7511->regmap,
> >> ADV7511_REG_INT_ENABLE(1),
> >> -                                  ADV7511_INT1_DDC_ERROR);
> >> -             }
> >> -             adv7511->current_edid_segment = -1;
> >> -     }
> >> +     if (!adv7511->powered)
> >> +             __adv7511_power_on(adv7511);
> > 
> > The __adv7511_power_on() function does more than the above, in particular
> > it performs an expensive regcache_sync() and calls adv7533_dsi_power_on()
> > for the ADV7533. Don't those operations have side effects that are either
> > not wanted or not needed here ? In any case this patch modifies the
> > behaviour of the driver, which needs to be documented in the kernel
> > message.
> 
> Sorry, what do you mean by kernel message? Commit message, maybe?

Sorry, yes, I meant commit message.

> Fair point, I'll review the adv7533_dsi_power_on bits and see if they
> should move out to the external function rather then the internal one.
> Similarly for the regcache_sync.
> 
> Thanks so much for the review!

-- 
Regards,

Laurent Pinchart