linux-kernel - Re: [PATCH 08/12] drm: bridge/dw_hdmi: avoid enabling interface in mode

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Message-ID: <5614969D.7030201@rock-chips.com>
Date:	Wed, 07 Oct 2015 11:50:53 +0800
From:	Yakir Yang <ykk@...k-chips.com>
To:	Russell King <rmk+kernel@....linux.org.uk>,
	linux-rockchip@...ts.infradead.org,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
CC:	Philipp Zabel <p.zabel@...gutronix.de>,
	Andy Yan <andy.yan@...k-chips.com>,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Jon Nettleton <jon.nettleton@...il.com>,
	David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH 08/12] drm: bridge/dw_hdmi: avoid enabling interface in
 mode_set



On 08/09/2015 12:04 AM, Russell King wrote:
> On a mode set, DRM makes the following sequence of calls:
> * for_each_encoder
> *   bridge	mode_fixup
> *   encoder	mode_fixup
> * crtc		mode_fixup
> * for_each_encoder
> *   bridge	disable
> *   encoder	prepare
> *   bridge	post_disable
> * disable unused encoders
> * crtc		prepare
> * crtc		mode_set
> * for_each_encoder
> *   encoder	mode_set
> *   bridge	mode_set
> * crtc		commit
> * for_each_encoder
> *   bridge	pre_enable
> *   encoder	commit
> *   bridge	enable
>
> dw_hdmi enables the HDMI output in both the bridge mode_set() and also
> the bridge enable() step.  This is duplicated work - we can avoid the
> setup in mode_set() and just do it in the enable() stage.  This
> simplifies the code a little.
>
> Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>

I have noticed that dw_hdmi driver have poweron/poweroff when
driver detect HPD event in irq thread, that's also duplicated works,
would you like to collect that changes into this one:

static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
{
         ......

         if (intr_stat & HDMI_IH_PHY_STAT0_HPD) {
                 if (phy_int_pol & HDMI_PHY_HPD) {
                         dev_dbg(hdmi->dev, "EVENT=plugin\n");

                         hdmi_modb(hdmi, 0, HDMI_PHY_HPD, HDMI_PHY_POL0);

                         dw_hdmi_poweron(hdmi);    // no need here
                 } else {
                         dev_dbg(hdmi->dev, "EVENT=plugout\n");

                         hdmi_modb(hdmi, HDMI_PHY_HPD, HDMI_PHY_HPD,
                                   HDMI_PHY_POL0);

                         dw_hdmi_poweroff(hdmi);    // no need here
                 }
                 drm_helper_hpd_irq_event(hdmi->connector.dev);
         }
         ......
}

Thanks,
- Yakir
> ---
>   drivers/gpu/drm/bridge/dw_hdmi.c | 2 --
>   1 file changed, 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
> index 578d7362cd65..fbac8386552b 100644
> --- a/drivers/gpu/drm/bridge/dw_hdmi.c
> +++ b/drivers/gpu/drm/bridge/dw_hdmi.c
> @@ -1389,8 +1389,6 @@ static void dw_hdmi_bridge_mode_set(struct drm_bridge *bridge,
>   {
>   	struct dw_hdmi *hdmi = bridge->driver_private;
>   
> -	dw_hdmi_setup(hdmi, mode);
> -
>   	/* Store the display mode for plugin/DKMS poweron events */
>   	memcpy(&hdmi->previous_mode, mode, sizeof(hdmi->previous_mode));
>   }


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