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Re: [PATCH 08/12] drm: bridge/dw_hdmi: avoid enabling interface in mode_set

Started byYakir Yang <ykk@rock-chips.com>
First post2015-10-07 06:00 +0200
Last post2015-10-07 11:40 +0200
Articles 3 — 2 participants

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  Re: [PATCH 08/12] drm: bridge/dw_hdmi: avoid enabling interface in  mode_set Yakir Yang <ykk@rock-chips.com> - 2015-10-07 06:00 +0200
    Re: [PATCH 08/12] drm: bridge/dw_hdmi: avoid enabling interface in  mode_set Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-10-07 11:20 +0200
      Re: [PATCH 08/12] drm: bridge/dw_hdmi: avoid enabling interface in  mode_set Yakir Yang <ykk@rock-chips.com> - 2015-10-07 11:40 +0200

#1241145 — Re: [PATCH 08/12] drm: bridge/dw_hdmi: avoid enabling interface in mode_set

FromYakir Yang <ykk@rock-chips.com>
Date2015-10-07 06:00 +0200
SubjectRe: [PATCH 08/12] drm: bridge/dw_hdmi: avoid enabling interface in mode_set
Message-ID<qgO3v-1C5-1@gated-at.bofh.it>

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@arm.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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#1241253

FromRussell King - ARM Linux <linux@arm.linux.org.uk>
Date2015-10-07 11:20 +0200
Message-ID<qgT3b-st-1@gated-at.bofh.it>
In reply to#1241145
On Wed, Oct 07, 2015 at 11:50:53AM +0800, Yakir Yang wrote:
> 
> 
> 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@arm.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);
>         }
>         ......
> }

I'm very much of the opinion of making small logical changes.  This
patch is one small logical change to the DRM-side logic to get rid
of the identified duplication there without touching anything else.
If removing the above calls to dw_hdmi_poweron()/dw_hdmi_poweroff()
were found to cause a regression, then the whole change would end
up being reverted, which would be annoying.

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#1241291

FromYakir Yang <ykk@rock-chips.com>
Date2015-10-07 11:40 +0200
Message-ID<qgTmx-P7-7@gated-at.bofh.it>
In reply to#1241253

On 10/07/2015 05:18 PM, Russell King - ARM Linux wrote:
> On Wed, Oct 07, 2015 at 11:50:53AM +0800, Yakir Yang wrote:
>>
>> 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@arm.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);
>>          }
>>          ......
>> }
> I'm very much of the opinion of making small logical changes.  This
> patch is one small logical change to the DRM-side logic to get rid
> of the identified duplication there without touching anything else.
> If removing the above calls to dw_hdmi_poweron()/dw_hdmi_poweroff()
> were found to cause a regression, then the whole change would end
> up being reverted, which would be annoying.

Hmm... Yeah, it do make some driver logical changes, but I
thought that's good, just make a clean on HPD thread, and I
do give lots of test on chrome tree about this changes, guess
a separate patch would be better.

If you don't feel good enough about this, okay, I would give
more test on that changes, and send upstream to request
comment later.

- Yakir

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