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Subject: Re: [PATCH] drm/msm/dp: deinitialize mainlink if link training failedo
From:   Stephen Boyd <swboyd@chromium.org>
Cc:     tanmay@codeaurora.org, abhinavk@codeaurora.org,
        aravindh@codeaurora.org, khsieh@codeaurora.org,
        rnayak@codeaurora.org, airlied@linux.ie, daniel@ffwll.ch,
        linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org
To:     Kuogee Hsieh <khsieh@codeaurora.org>, robdclark@gmail.com,
        sean@poorly.run
Date:   Mon, 02 Nov 2020 12:59:48 -0800
Message-ID: <160435078857.884498.13223713108695196370@swboyd.mtv.corp.google.com>
User-Agent: alot/0.9.1
Precedence: bulk

Quoting Kuogee Hsieh (2020-10-30 16:22:53)
> DP compo phy have to be enable to start link training. When
> link training failed phy need to be disabled so that next
> link trainng can be proceed smoothly at next plug in. This

s/trainng/training/

> patch de initialize mainlink to disable phy if link training

s/de/de-/

> failed. This prevent system crash due to
> disp_cc_mdss_dp_link_intf_clk stuck at "off" state.  This patch
> also perform checking power_on flag at dp_display_enable() and
> dp_display_disable() to avoid crashing when unplug cable while
> display is off.
>=20
> Fixes: fdaf9a5e3c15 (drm/msm/dp: fixes wrong connection state caused by f=
ailure of link train
>=20

Drop newline please.

> Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
> ---

Can you send this as a patch series? There were three patches sent near
each other and presumably they're related.

>  drivers/gpu/drm/msm/dp/dp_ctrl.c    | 34 +++++++++++++++++++++++++++--
>  drivers/gpu/drm/msm/dp/dp_display.c | 13 +++++++++++
>  2 files changed, 45 insertions(+), 2 deletions(-)
>=20
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp=
_ctrl.c
> index cee161c8ecc6..904698dfc7f7 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1468,6 +1468,29 @@ static int dp_ctrl_reinitialize_mainlink(struct dp=
_ctrl_private *ctrl)
>         return ret;
>  }
> =20
> +static int dp_ctrl_deinitialize_mainlink(struct dp_ctrl_private *ctrl)
> +{
> +       struct dp_io *dp_io;
> +       struct phy *phy;
> +       int ret =3D 0;

Please drop this initialization to 0.

> +
> +       dp_io =3D &ctrl->parser->io;
> +       phy =3D dp_io->phy;
> +
> +       dp_catalog_ctrl_mainlink_ctrl(ctrl->catalog, false);
> +
> +       dp_catalog_ctrl_reset(ctrl->catalog);
> +
> +       ret =3D dp_power_clk_enable(ctrl->power, DP_CTRL_PM, false);

As it's overwritten here.

> +       if (ret)
> +               DRM_ERROR("Failed to disable link clocks. ret=3D%d\n", re=
t);
> +
> +       phy_power_off(phy);
> +       phy_exit(phy);
> +
> +       return -ECONNRESET;

Isn't this an error for networking connections getting reset? Really it
should return 0 because it didn't fail.

> +}
> +
>  static int dp_ctrl_link_maintenance(struct dp_ctrl_private *ctrl)
>  {
>         int ret =3D 0;
> @@ -1648,8 +1671,7 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
>         if (rc)
>                 return rc;
> =20
> -       while (--link_train_max_retries &&
> -               !atomic_read(&ctrl->dp_ctrl.aborted)) {
> +       while (--link_train_max_retries) {
>                 rc =3D dp_ctrl_reinitialize_mainlink(ctrl);
>                 if (rc) {
>                         DRM_ERROR("Failed to reinitialize mainlink. rc=3D=
%d\n",
> @@ -1664,6 +1686,9 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
>                         break;
>                 } else if (training_step =3D=3D DP_TRAINING_1) {
>                         /* link train_1 failed */
> +                       if (!dp_catalog_hpd_get_state_status(ctrl->catalo=
g))
> +                               break;          /* link cable unplugged */
> +
>                         rc =3D dp_ctrl_link_rate_down_shift(ctrl);
>                         if (rc < 0) { /* already in RBR =3D 1.6G */
>                                 if (cr.lane_0_1 & DP_LANE0_1_CR_DONE) {
> @@ -1683,6 +1708,9 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
>                         }
>                 } else if (training_step =3D=3D DP_TRAINING_2) {
>                         /* link train_2 failed, lower lane rate */
> +                       if (!dp_catalog_hpd_get_state_status(ctrl->catalo=
g))

Maybe make a function called dp_catalog_link_disconnected()? Then the
comment isn't needed.

> +                               break;          /* link cable unplugged */
> +
>                         rc =3D dp_ctrl_link_lane_down_shift(ctrl);
>                         if (rc < 0) {
>                                 /* end with failure */
> @@ -1703,6 +1731,8 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
>          */
>         if (rc =3D=3D 0)  /* link train successfully */
>                 dp_ctrl_push_idle(dp_ctrl);
> +       else
> +               rc =3D dp_ctrl_deinitialize_mainlink(ctrl);

So if it fails we deinitialize and then return success? Shouldn't we
keep the error code from the link train attempt instead of overwrite it
with (most likely) zero? I see that it returns -ECONNRESET but that's
really odd and seeing this code here means you have to look at the
function to figure out that it's still returning an error code. Please
don't do that, just ignore the error code from this function.

> =20
>         return rc;
>  }
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp=
/dp_display.c
> index 3eb0d428abf7..13b66266cd69 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -529,6 +529,11 @@ static int dp_hpd_plug_handle(struct dp_display_priv=
ate *dp, u32 data)
>         if (ret) {      /* link train failed */
>                 hpd->hpd_high =3D 0;
>                 dp->hpd_state =3D ST_DISCONNECTED;
> +
> +               if (ret =3D=3D -ECONNRESET) { /* cable unplugged */
> +                       dp->core_initialized =3D false;
> +               }

Style: Drop braces on single line if statements.

> +
>         } else {
>                 /* start sentinel checking in case of missing uevent */
>                 dp_add_event(dp, EV_CONNECT_PENDING_TIMEOUT, 0, tout);
> @@ -794,6 +799,11 @@ static int dp_display_enable(struct dp_display_priva=
te *dp, u32 data)
> =20
>         dp_display =3D g_dp_display;
> =20
> +       if (dp_display->power_on) {
> +               DRM_DEBUG_DP("Link already setup, return\n");
> +               return 0;
> +       }
> +
>         rc =3D dp_ctrl_on_stream(dp->ctrl);
>         if (!rc)
>                 dp_display->power_on =3D true;
> @@ -826,6 +836,9 @@ static int dp_display_disable(struct dp_display_priva=
te *dp, u32 data)
> =20
>         dp_display =3D g_dp_display;
> =20
> +       if (!dp_display->power_on)
> +               return -EINVAL;
> +
>         /* wait only if audio was enabled */
>         if (dp_display->audio_enabled) {
>                 if (!wait_for_completion_timeout(&dp->audio_comp,
>=20
> base-commit: fd4a29bed29b3d8f15942fdf77e7a0a52796d836

What is this commit?