On Mon, 24 Oct 2016, Imre Deak <imre.d...@intel.com> wrote:
> On my APL the LSPCON firmware resumes in PCON mode as opposed to the
> expected LS mode. It also appears to be in a state where AUX DPCD reads
> will succeed but return garbage recovering only after a few hundreds of
> milliseconds. After the recovery time DPCD reads will result in the
> correct values and things will continue to work. If I2C over AUX is
> attempted during this recovery time (implying an AUX write transaction)
> the firmware won't recover and will stay in this broken state.
>
> As a workaround check if the firmware is in PCON state after resume and
> if so wait until the correct DPCD values are returned. For this we
> compare the branch descriptor with the one we cached during init time.
> If the firmware was in the LS state, we skip the w/a and continue as
> before.
>
> v2:
> - Use the DP descriptor value cached in intel_dp. (Jani)
> - Get to intel_dp using container_of(), instead of a cached ptr.
> (Shashank)
> - Use usleep_range() instead of msleep().
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98353
> Cc: Shashank Sharma <shashank.sha...@intel.com>
> Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
> Cc: Jani Nikula <jani.nik...@intel.com>
> Signed-off-by: Imre Deak <imre.d...@intel.com>
I don't think we properly understand what's going on with the device. In
the mean time, limp on with this if this fixes stuff.
Acked-by: Jani Nikula <jani.nik...@intel.com>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 2 +-
> drivers/gpu/drm/i915/intel_drv.h | 3 +++
> drivers/gpu/drm/i915/intel_lspcon.c | 37
> ++++++++++++++++++++++++++++++++++++-
> 3 files changed, 40 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 043993f..e9be955 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1451,7 +1451,7 @@ static void intel_dp_print_rates(struct intel_dp
> *intel_dp)
> DRM_DEBUG_KMS("common rates: %s\n", str);
> }
>
> -static bool
> +bool
> __intel_dp_read_desc(struct intel_dp *intel_dp, struct intel_dp_desc *desc)
> {
> u32 base = drm_dp_is_branch(intel_dp->dpcd) ? DP_BRANCH_OUI :
> diff --git a/drivers/gpu/drm/i915/intel_drv.h
> b/drivers/gpu/drm/i915/intel_drv.h
> index 45f55b5..f2b6c59 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -974,6 +974,7 @@ struct intel_dp {
> struct intel_lspcon {
> bool active;
> enum drm_lspcon_mode mode;
> + bool desc_valid;
> };
>
> struct intel_digital_port {
> @@ -1461,6 +1462,8 @@ static inline unsigned int
> intel_dp_unused_lane_mask(int lane_count)
> }
>
> bool intel_dp_read_dpcd(struct intel_dp *intel_dp);
> +bool __intel_dp_read_desc(struct intel_dp *intel_dp,
> + struct intel_dp_desc *desc);
> bool intel_dp_read_desc(struct intel_dp *intel_dp);
>
> /* intel_dp_aux_backlight.c */
> diff --git a/drivers/gpu/drm/i915/intel_lspcon.c
> b/drivers/gpu/drm/i915/intel_lspcon.c
> index 3dc5a0b..daa5234 100644
> --- a/drivers/gpu/drm/i915/intel_lspcon.c
> +++ b/drivers/gpu/drm/i915/intel_lspcon.c
> @@ -97,8 +97,43 @@ static bool lspcon_probe(struct intel_lspcon *lspcon)
> return true;
> }
>
> +static void lspcon_resume_in_pcon_wa(struct intel_lspcon *lspcon)
> +{
> + struct intel_dp *intel_dp = lspcon_to_intel_dp(lspcon);
> + unsigned long start = jiffies;
> +
> + if (!lspcon->desc_valid)
> + return;
> +
> + while (1) {
> + struct intel_dp_desc desc;
> +
> + /*
> + * The w/a only applies in PCON mode and we don't expect any
> + * AUX errors.
> + */
> + if (!__intel_dp_read_desc(intel_dp, &desc))
> + return;
> +
> + if (!memcmp(&intel_dp->desc, &desc, sizeof(desc))) {
> + DRM_DEBUG_KMS("LSPCON recovering in PCON mode after %u
> ms\n",
> + jiffies_to_msecs(jiffies - start));
> + return;
> + }
> +
> + if (time_after(jiffies, start + msecs_to_jiffies(1000)))
> + break;
> +
> + usleep_range(10000, 15000);
> + }
> +
> + DRM_DEBUG_KMS("LSPCON DP descriptor mismatch after resume\n");
> +}
> +
> void lspcon_resume(struct intel_lspcon *lspcon)
> {
> + lspcon_resume_in_pcon_wa(lspcon);
> +
> if (lspcon_change_mode(lspcon, DRM_LSPCON_MODE_PCON, true))
> DRM_ERROR("LSPCON resume failed\n");
> else
> @@ -143,7 +178,7 @@ bool lspcon_init(struct intel_digital_port
> *intel_dig_port)
> return false;
> }
>
> - intel_dp_read_desc(dp);
> + lspcon->desc_valid = intel_dp_read_desc(dp);
>
> DRM_DEBUG_KMS("Success: LSPCON init\n");
> return true;
--
Jani Nikula, Intel Open Source Technology Center
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