linux-kernel - Re: [PATCH] drm/msm/dp: handle irq_hpd with sink

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Date:   Mon, 10 May 2021 11:15:16 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <khsieh@...eaurora.org>, agross@...nel.org,
        bjorn.andersson@...aro.org, robdclark@...il.com, sean@...rly.run,
        vkoul@...nel.org
Cc:     abhinavk@...eaurora.org, aravindh@...eaurora.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dp: handle irq_hpd with sink_count = 0 correctly

Quoting Kuogee Hsieh (2021-05-05 14:52:01)
> irq_hpd interrupt should be handled after dongle plugged in and
> before dongle unplugged. Hence irq_hpd interrupt is enabled at
> the end of the plugin handle and disabled at the beginning of
> unplugged handle. Current irq_hpd with sink_count = 0 is wrongly
> handled same as the dongle unplugged which tears down the mainlink
> and disables the phy. This patch fixes this problem by only tearing
> down the mainlink but keeping phy enabled at irq_hpd with
> sink_count = 0 handle so that next irq_hpe with sink_count =1 can be
> handled by setup mainlink only.
>
> Signed-off-by: Kuogee Hsieh <khsieh@...eaurora.org>
> ---

It works for me, but I question the poking into phy internals below.

>  drivers/gpu/drm/msm/dp/dp_catalog.c |  5 +--
>  drivers/gpu/drm/msm/dp/dp_ctrl.c    | 78 +++++++++++++++++++++++++++++++++----
>  drivers/gpu/drm/msm/dp/dp_ctrl.h    |  2 +
>  drivers/gpu/drm/msm/dp/dp_display.c | 47 +++++++++++++++++-----
>  4 files changed, 111 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_catalog.c b/drivers/gpu/drm/msm/dp/dp_catalog.c
> index b1a9b1b..f4f53f2 100644
> --- a/drivers/gpu/drm/msm/dp/dp_catalog.c
> +++ b/drivers/gpu/drm/msm/dp/dp_catalog.c
> @@ -582,10 +582,9 @@ void dp_catalog_ctrl_hpd_config(struct dp_catalog *dp_catalog)
>
>         u32 reftimer = dp_read_aux(catalog, REG_DP_DP_HPD_REFTIMER);
>
> -       /* enable HPD interrupts */
> +       /* enable HPD plug and unplug interrupts */
>         dp_catalog_hpd_config_intr(dp_catalog,
> -               DP_DP_HPD_PLUG_INT_MASK | DP_DP_IRQ_HPD_INT_MASK
> -               | DP_DP_HPD_UNPLUG_INT_MASK | DP_DP_HPD_REPLUG_INT_MASK, true);
> +               DP_DP_HPD_PLUG_INT_MASK | DP_DP_HPD_UNPLUG_INT_MASK, true);
>
>         /* Configure REFTIMER and enable it */
>         reftimer |= DP_DP_HPD_REFTIMER_ENABLE;
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index 8d59eb9..5922259 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1334,8 +1334,10 @@ static int dp_ctrl_enable_mainlink_clocks(struct dp_ctrl_private *ctrl)
>         dp_ctrl_set_clock_rate(ctrl, DP_CTRL_PM, "ctrl_link",
>                                         ctrl->link->link_params.rate * 1000);
>
> -       phy_configure(phy, &dp_io->phy_opts);
> -       phy_power_on(phy);
> +       if (!phy->power_count) {
> +               phy_configure(phy, &dp_io->phy_opts);
> +               phy_power_on(phy);
> +       }
>
>         ret = dp_power_clk_enable(ctrl->power, DP_CTRL_PM, true);
>         if (ret)
> @@ -1414,6 +1416,10 @@ void dp_ctrl_host_deinit(struct dp_ctrl *dp_ctrl)
>         phy = dp_io->phy;
>
>         dp_catalog_ctrl_enable_irq(ctrl->catalog, false);
> +
> +       if (phy->power_count)
> +               phy_power_off(phy);
> +
>         phy_exit(phy);
>
>         DRM_DEBUG_DP("Host deinitialized successfully\n");
> @@ -1445,7 +1451,6 @@ static int dp_ctrl_reinitialize_mainlink(struct dp_ctrl_private *ctrl)
>
>         dp_catalog_ctrl_mainlink_ctrl(ctrl->catalog, false);
>         opts_dp->lanes = ctrl->link->link_params.num_lanes;
> -       phy_configure(phy, &dp_io->phy_opts);
>         /*
>          * Disable and re-enable the mainlink clock since the
>          * link clock might have been adjusted as part of the
> @@ -1456,9 +1461,13 @@ static int dp_ctrl_reinitialize_mainlink(struct dp_ctrl_private *ctrl)
>                 DRM_ERROR("Failed to disable clocks. ret=%d\n", ret);
>                 return ret;
>         }
> -       phy_power_off(phy);
> -       /* hw recommended delay before re-enabling clocks */
> -       msleep(20);
> +
> +       if (phy->power_count) {

I don't believe members of 'phy' are supposed to be looked at by various
phy consumer drivers. Vinod, is that right?

> +               phy_configure(phy, &dp_io->phy_opts);
> +               phy_power_off(phy);
> +               /* hw recommended delay before re-enabling clocks */
> +               msleep(20);
> +       }
>
>         ret = dp_ctrl_enable_mainlink_clocks(ctrl);
>         if (ret) {
> @@ -1487,7 +1496,9 @@ static int dp_ctrl_deinitialize_mainlink(struct dp_ctrl_private *ctrl)
>                 DRM_ERROR("Failed to disable link clocks. ret=%d\n", ret);
>         }
>
> -       phy_power_off(phy);
> +       if (phy->power_count)
> +               phy_power_off(phy);
> +

Given that init/power_on are both refcounted, maybe the code could call
phy_init()/phy_exit() when hpd changes, i.e. the link is up and
phy_power_on()/phy_power_off() when the mainlink is supposed to be
enabled (I guess when we're going to display bit to the screen?). That
way we don't have to check the counts.

>         phy_exit(phy);
>
>         return 0;