[PATCH v4 0/2] cleared DP_DOWNSPREAD_CTRL register

[PATCH v4 0/2] cleared DP_DOWNSPREAD_CTRL register

[Kuogee Hsieh]

cleared DP_DOWNSPREAD_CTRL register before start link training

Kuogee Hsieh (2):
  drm/msm/dp: cleared DP_DOWNSPREAD_CTRL register before start link
    training
  drm/msm/dp: retry 3 times if set sink to D0 poweer state failed

 drivers/gpu/drm/msm/dp/dp_ctrl.c | 13 +++++--------
 drivers/gpu/drm/msm/dp/dp_link.c | 21 ++++++++++++---------
 2 files changed, 17 insertions(+), 17 deletions(-)

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v4 1/2] drm/msm/dp: cleared DP_DOWNSPREAD_CTRL register before start link training

[Kuogee Hsieh]

DOWNSPREAD_CTRL (0x107) shall be cleared to 0 upon power-on reset or an
upstream device disconnect. This patch will enforce this rule by always
cleared DOWNSPREAD_CTRL register to 0 before start link training. At rare
case that DP MSA timing parameters may be mis-interpreted by the sink
which causes audio sampling rate be calculated wrongly and cause audio
did not work at sink if DOWNSPREAD_CTRL register is not cleared to 0.

Changes in v2:
1) fix spelling at commit text
2) merge ssc variable into encoding[0]

Changes in v3:
-- correct spelling of DOWNSPREAD_CTRL
-- replace err with len of ssize_t

Changes in v4:
-- split into 2 patches

Fixes: 154b5a7da0fd ("drm/msm/dp: add displayPort driver support")
Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
---
 drivers/gpu/drm/msm/dp/dp_ctrl.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
index ab6aa13..2c74c59 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
@@ -1245,8 +1245,7 @@ static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
 {
 	int ret = 0;
 	const u8 *dpcd = ctrl->panel->dpcd;
-	u8 encoding = DP_SET_ANSI_8B10B;
-	u8 ssc;
+	u8 encoding[] = { 0, DP_SET_ANSI_8B10B };
 	u8 assr;
 	struct dp_link_info link_info = {0};
 
@@ -1258,13 +1257,11 @@ static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
 
 	dp_aux_link_configure(ctrl->aux, &link_info);
 
-	if (drm_dp_max_downspread(dpcd)) {
-		ssc = DP_SPREAD_AMP_0_5;
-		drm_dp_dpcd_write(ctrl->aux, DP_DOWNSPREAD_CTRL, &ssc, 1);
-	}
+	if (drm_dp_max_downspread(dpcd))
+		encoding[0] |= DP_SPREAD_AMP_0_5;
 
-	drm_dp_dpcd_write(ctrl->aux, DP_MAIN_LINK_CHANNEL_CODING_SET,
-				&encoding, 1);
+	/* config DOWNSPREAD_CTRL and MAIN_LINK_CHANNEL_CODING_SET */
+	drm_dp_dpcd_write(ctrl->aux, DP_DOWNSPREAD_CTRL, encoding, 2);
 
 	if (drm_dp_alternate_scrambler_reset_cap(dpcd)) {
 		assr = DP_ALTERNATE_SCRAMBLER_RESET_ENABLE;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v4 2/2] drm/msm/dp: retry 3 times if set sink to D0 poweer state failed

[Kuogee Hsieh]

Bring sink out of D3 (power down) mode into D0 (normal operation) mode
by setting DP_SET_POWER_D0 bit to DP_SET_POWER dpcd register. This
patch will retry 3 times if written to DP_SET_POWER register failed.

Changes in v4:
-- split into two patches

Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
---
 drivers/gpu/drm/msm/dp/dp_link.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_link.c b/drivers/gpu/drm/msm/dp/dp_link.c
index 36f0af0..7b5ecf5 100644
--- a/drivers/gpu/drm/msm/dp/dp_link.c
+++ b/drivers/gpu/drm/msm/dp/dp_link.c
@@ -49,23 +49,26 @@ static int dp_aux_link_power_up(struct drm_dp_aux *aux,
 					struct dp_link_info *link)
 {
 	u8 value;
-	int err;
+	ssize_t len;
+	int i;
 
 	if (link->revision < 0x11)
 		return 0;
 
-	err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
-	if (err < 0)
-		return err;
+	len = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
+	if (len < 0)
+		return len;
 
 	value &= ~DP_SET_POWER_MASK;
 	value |= DP_SET_POWER_D0;
 
-	err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
-	if (err < 0)
-		return err;
-
-	usleep_range(1000, 2000);
+	/* retry for 1ms to give the sink time to wake up */
+	for (i = 0; i < 3; i++) {
+	        len = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
+		usleep_range(1000, 2000);
+		if (len == 1)
+			break;
+	}
 
 	return 0;
 }
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v4 2/2] drm/msm/dp: retry 3 times if set sink to D0 poweer state failed

[Dmitry Baryshkov]

On Fri, 9 Sept 2022 at 00:18, Kuogee Hsieh <quic_khsieh@quicinc.com> wrote:
>
> Bring sink out of D3 (power down) mode into D0 (normal operation) mode
> by setting DP_SET_POWER_D0 bit to DP_SET_POWER dpcd register. This
> patch will retry 3 times if written to DP_SET_POWER register failed.
>
> Changes in v4:
> -- split into two patches
>
> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
> ---
>  drivers/gpu/drm/msm/dp/dp_link.c | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_link.c b/drivers/gpu/drm/msm/dp/dp_link.c
> index 36f0af0..7b5ecf5 100644
> --- a/drivers/gpu/drm/msm/dp/dp_link.c
> +++ b/drivers/gpu/drm/msm/dp/dp_link.c
> @@ -49,23 +49,26 @@ static int dp_aux_link_power_up(struct drm_dp_aux *aux,
>                                         struct dp_link_info *link)
>  {
>         u8 value;
> -       int err;
> +       ssize_t len;
> +       int i;
>
>         if (link->revision < 0x11)
>                 return 0;
>
> -       err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
> -       if (err < 0)
> -               return err;
> +       len = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
> +       if (len < 0)
> +               return len;

This is a separate patch.

>
>         value &= ~DP_SET_POWER_MASK;
>         value |= DP_SET_POWER_D0;
>
> -       err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
> -       if (err < 0)
> -               return err;
> -
> -       usleep_range(1000, 2000);
> +       /* retry for 1ms to give the sink time to wake up */
> +       for (i = 0; i < 3; i++) {
> +               len = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
> +               usleep_range(1000, 2000);
> +               if (len == 1)
> +                       break;
> +       }
>
>         return 0;
>  }
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>


-- 
With best wishes
Dmitry