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

From: Laurent Pinchart
Date: Tue Nov 22 2016 - 03:14:21 EST


Hi John,

Thank you for the patch.

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@xxxxxxxx>
> Cc: Archit Taneja <architt@xxxxxxxxxxxxxx>
> Cc: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
> Cc: Lars-Peter Clausen <lars@xxxxxxxxxx>
> Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
> ---
> 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.

> /*
> * 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.

> edid = drm_do_get_edid(connector, adv7511_get_edid_block, adv7511);
>
> if (!adv7511->powered)
> - regmap_update_bits(adv7511->regmap, ADV7511_REG_POWER,
> - ADV7511_POWER_POWER_DOWN,
> - ADV7511_POWER_POWER_DOWN);
> + __adv7511_power_off(adv7511);
>
> kfree(adv7511->edid);
> adv7511->edid = edid;

--
Regards,

Laurent Pinchart