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

[Yakir Yang]

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@xxxxxxxxxxxxxxxx>
> > 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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