linux-kernel - Re: [PATCH 2/2] drm/msm/dp: unplug interrupt missed after irq

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Message-ID: <161056938760.3661239.7140156995833982843@swboyd.mtv.corp.google.com>
Date:   Wed, 13 Jan 2021 12:23:07 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     khsieh@...eaurora.org
Cc:     dri-devel@...ts.freedesktop.org, robdclark@...il.com,
        sean@...rly.run, tanmay@...eaurora.org, abhinavk@...eaurora.org,
        aravindh@...eaurora.org, airlied@...ux.ie, daniel@...ll.ch,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/msm/dp: unplug interrupt missed after irq_hpd handler

Quoting khsieh@...eaurora.org (2021-01-13 09:48:25)
> On 2021-01-11 11:54, Stephen Boyd wrote:
> > Quoting Kuogee Hsieh (2021-01-07 12:30:25)
> >> There is HPD unplug interrupts missed at scenario of an irq_hpd
> >> followed by unplug interrupts with around 10 ms in between.
> >> Since both AUX_SW_RESET and DP_SW_RESET clear pending HPD interrupts,
> >> irq_hpd handler should not issues either aux or sw reset to avoid
> >> following unplug interrupt be cleared accidentally.
> > 
> > So the problem is that we're resetting the DP aux phy in the middle of
> > the HPD state machine transitioning states?
> > 
> yes, after reset aux, hw clear pending hpd interrupts
> >> 
> >> Signed-off-by: Kuogee Hsieh <khsieh@...eaurora.org>
> >> ---
> >> diff --git a/drivers/gpu/drm/msm/dp/dp_catalog.c 
> >> b/drivers/gpu/drm/msm/dp/dp_catalog.c
> >> index 44f0c57..9c0ce98 100644
> >> --- a/drivers/gpu/drm/msm/dp/dp_catalog.c
> >> +++ b/drivers/gpu/drm/msm/dp/dp_catalog.c
> >> @@ -190,6 +190,18 @@ int dp_catalog_aux_clear_hw_interrupts(struct 
> >> dp_catalog *dp_catalog)
> >>         return 0;
> >>  }
> >> 
> >> +/**
> >> + * dp_catalog_aux_reset() - reset AUX controller
> >> + *
> >> + * @aux: DP catalog structure
> >> + *
> >> + * return: void
> >> + *
> >> + * This function reset AUX controller
> >> + *
> >> + * NOTE: reset AUX controller will also clear any pending HPD related 
> >> interrupts
> >> + *
> >> + */
> >>  void dp_catalog_aux_reset(struct dp_catalog *dp_catalog)
> >>  {
> >>         u32 aux_ctrl;
> >> @@ -483,6 +495,18 @@ int dp_catalog_ctrl_set_pattern(struct dp_catalog 
> >> *dp_catalog,
> >>         return 0;
> >>  }
> >> 
> >> +/**
> >> + * dp_catalog_ctrl_reset() - reset DP controller
> >> + *
> >> + * @aux: DP catalog structure
> > 
> > It's called dp_catalog though.
> registers access are through dp_catalog_xxxx

Agreed. The variable is not called 'aux' though, it's called
'dp_catalog'.

> > 
> >> + *
> >> + * return: void
> >> + *
> >> + * This function reset DP controller
> > 
> > resets the
> > 
> >> + *
> >> + * NOTE: reset DP controller will also clear any pending HPD related 
> >> interrupts
> >> + *
> >> + */
> >>  void dp_catalog_ctrl_reset(struct dp_catalog *dp_catalog)

Right here.

> >>  {
> >>         u32 sw_reset;
> >> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c 
> >> b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> >> index e3462f5..f96c415 100644
> >> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> >> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> >> @@ -1296,7 +1296,8 @@ static int dp_ctrl_setup_main_link(struct 
> >> dp_ctrl_private *ctrl,
> >>          * transitioned to PUSH_IDLE. In order to start transmitting
> >>          * a link training pattern, we have to first do soft reset.
> >>          */
> >> -       dp_catalog_ctrl_reset(ctrl->catalog);
> >> +       if (*training_step != DP_TRAINING_NONE)
> > 
> > Can we check for the positive value instead? i.e.
> > DP_TRAINING_1/DP_TRAINING_2
> > 

Any answer?