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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 22 Nov 2016 10:14:33 +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
Subject: Re: [RFC][PATCH 1/3] drm/bridge: adv7511: Rework adv7511_power_on/off() so they can be reused internally

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@...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.

>  	/*
>  	 * 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