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[PATCH RFC 1/4] drm/dp: Add helper to set LTTPRs in transparent mode

Abel Vesa posted 4 patches 3 weeks, 3 days ago
[PATCH RFC 1/4] drm/dp: Add helper to set LTTPRs in transparent mode
Posted by Abel Vesa 3 weeks, 3 days ago 
According to the DisplayPort standard, LTTPRs have two operating
modes:
 - non-transparent - it replies to DPCD LTTPR field specific AUX
   requests, while passes through all other AUX requests
 - transparent - it passes through all AUX requests.

Switching between this two modes is done by the DPTX by issuing
an AUX write to the DPCD PHY_REPEATER_MODE register.

Add a generic helper that allows switching between these modes.

Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
---
 drivers/gpu/drm/display/drm_dp_helper.c | 17 +++++++++++++++++
 include/drm/display/drm_dp_helper.h     |  1 +
 2 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
index 6ee51003de3ce616c3a52653c2f1979ad7658e21..38d612345986ad54b42228902ea718a089d169c4 100644
--- a/drivers/gpu/drm/display/drm_dp_helper.c
+++ b/drivers/gpu/drm/display/drm_dp_helper.c
@@ -2694,6 +2694,23 @@ int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE])
 }
 EXPORT_SYMBOL(drm_dp_lttpr_max_link_rate);
 
+/**
+ * drm_dp_lttpr_set_transparent_mode - set the LTTPR in transparent mode
+ * @aux: DisplayPort AUX channel
+ * @enable: Enable or disable transparent mode
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+
+int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable)
+{
+	u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT :
+			  DP_PHY_REPEATER_MODE_NON_TRANSPARENT;
+
+	return drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE, val);
+}
+EXPORT_SYMBOL(drm_dp_lttpr_set_transparent_mode);
+
 /**
  * drm_dp_lttpr_max_lane_count - get the maximum lane count supported by all LTTPRs
  * @caps: LTTPR common capabilities
diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
index 279624833ea9259809428162f4e845654359f8c9..8821ab2d36b0e04d38ccbdddcb703b34de7ed680 100644
--- a/include/drm/display/drm_dp_helper.h
+++ b/include/drm/display/drm_dp_helper.h
@@ -625,6 +625,7 @@ int drm_dp_read_lttpr_phy_caps(struct drm_dp_aux *aux,
 			       u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
 int drm_dp_lttpr_count(const u8 cap[DP_LTTPR_COMMON_CAP_SIZE]);
 int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
+int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable);
 int drm_dp_lttpr_max_lane_count(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
 bool drm_dp_lttpr_voltage_swing_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
 bool drm_dp_lttpr_pre_emphasis_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);

-- 
2.34.1
Re: [PATCH RFC 1/4] drm/dp: Add helper to set LTTPRs in transparent mode
Posted by Imre Deak 3 weeks, 3 days ago 
On Thu, Oct 31, 2024 at 05:12:45PM +0200, Abel Vesa wrote:
> According to the DisplayPort standard, LTTPRs have two operating
> modes:
>  - non-transparent - it replies to DPCD LTTPR field specific AUX
>    requests, while passes through all other AUX requests
>  - transparent - it passes through all AUX requests.
> 
> Switching between this two modes is done by the DPTX by issuing
> an AUX write to the DPCD PHY_REPEATER_MODE register.
> 
> Add a generic helper that allows switching between these modes.
> 
> Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
> ---
>  drivers/gpu/drm/display/drm_dp_helper.c | 17 +++++++++++++++++
>  include/drm/display/drm_dp_helper.h     |  1 +
>  2 files changed, 18 insertions(+)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> index 6ee51003de3ce616c3a52653c2f1979ad7658e21..38d612345986ad54b42228902ea718a089d169c4 100644
> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> @@ -2694,6 +2694,23 @@ int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE])
>  }
>  EXPORT_SYMBOL(drm_dp_lttpr_max_link_rate);
>  
> +/**
> + * drm_dp_lttpr_set_transparent_mode - set the LTTPR in transparent mode
> + * @aux: DisplayPort AUX channel
> + * @enable: Enable or disable transparent mode
> + *
> + * Returns 0 on success or a negative error code on failure.

Should be "Returns 1 on success".

> + */
> +
> +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable)
> +{
> +	u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT :
> +			  DP_PHY_REPEATER_MODE_NON_TRANSPARENT;
> +
> +	return drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE, val);
> +}
> +EXPORT_SYMBOL(drm_dp_lttpr_set_transparent_mode);
> +
>  /**
>   * drm_dp_lttpr_max_lane_count - get the maximum lane count supported by all LTTPRs
>   * @caps: LTTPR common capabilities
> diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
> index 279624833ea9259809428162f4e845654359f8c9..8821ab2d36b0e04d38ccbdddcb703b34de7ed680 100644
> --- a/include/drm/display/drm_dp_helper.h
> +++ b/include/drm/display/drm_dp_helper.h
> @@ -625,6 +625,7 @@ int drm_dp_read_lttpr_phy_caps(struct drm_dp_aux *aux,
>  			       u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
>  int drm_dp_lttpr_count(const u8 cap[DP_LTTPR_COMMON_CAP_SIZE]);
>  int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
> +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable);
>  int drm_dp_lttpr_max_lane_count(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
>  bool drm_dp_lttpr_voltage_swing_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
>  bool drm_dp_lttpr_pre_emphasis_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
> 
> -- 
> 2.34.1
>
Re: [PATCH RFC 1/4] drm/dp: Add helper to set LTTPRs in transparent mode
Posted by Jani Nikula 3 weeks, 2 days ago 
On Thu, 31 Oct 2024, Imre Deak <imre.deak@intel.com> wrote:
> On Thu, Oct 31, 2024 at 05:12:45PM +0200, Abel Vesa wrote:
>> According to the DisplayPort standard, LTTPRs have two operating
>> modes:
>>  - non-transparent - it replies to DPCD LTTPR field specific AUX
>>    requests, while passes through all other AUX requests
>>  - transparent - it passes through all AUX requests.
>> 
>> Switching between this two modes is done by the DPTX by issuing
>> an AUX write to the DPCD PHY_REPEATER_MODE register.
>> 
>> Add a generic helper that allows switching between these modes.
>> 
>> Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
>> ---
>>  drivers/gpu/drm/display/drm_dp_helper.c | 17 +++++++++++++++++
>>  include/drm/display/drm_dp_helper.h     |  1 +
>>  2 files changed, 18 insertions(+)
>> 
>> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
>> index 6ee51003de3ce616c3a52653c2f1979ad7658e21..38d612345986ad54b42228902ea718a089d169c4 100644
>> --- a/drivers/gpu/drm/display/drm_dp_helper.c
>> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
>> @@ -2694,6 +2694,23 @@ int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE])
>>  }
>>  EXPORT_SYMBOL(drm_dp_lttpr_max_link_rate);
>>  
>> +/**
>> + * drm_dp_lttpr_set_transparent_mode - set the LTTPR in transparent mode
>> + * @aux: DisplayPort AUX channel
>> + * @enable: Enable or disable transparent mode
>> + *
>> + * Returns 0 on success or a negative error code on failure.
>
> Should be "Returns 1 on success".

But is that a sensible return value?

>
>> + */
>> +

Superfluous newline.

>> +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable)
>> +{
>> +	u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT :
>> +			  DP_PHY_REPEATER_MODE_NON_TRANSPARENT;
>> +
>> +	return drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE, val);
>> +}
>> +EXPORT_SYMBOL(drm_dp_lttpr_set_transparent_mode);
>> +
>>  /**
>>   * drm_dp_lttpr_max_lane_count - get the maximum lane count supported by all LTTPRs
>>   * @caps: LTTPR common capabilities
>> diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
>> index 279624833ea9259809428162f4e845654359f8c9..8821ab2d36b0e04d38ccbdddcb703b34de7ed680 100644
>> --- a/include/drm/display/drm_dp_helper.h
>> +++ b/include/drm/display/drm_dp_helper.h
>> @@ -625,6 +625,7 @@ int drm_dp_read_lttpr_phy_caps(struct drm_dp_aux *aux,
>>  			       u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
>>  int drm_dp_lttpr_count(const u8 cap[DP_LTTPR_COMMON_CAP_SIZE]);
>>  int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
>> +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable);
>>  int drm_dp_lttpr_max_lane_count(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
>>  bool drm_dp_lttpr_voltage_swing_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
>>  bool drm_dp_lttpr_pre_emphasis_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
>> 
>> -- 
>> 2.34.1
>> 

-- 
Jani Nikula, Intel
Re: [PATCH RFC 1/4] drm/dp: Add helper to set LTTPRs in transparent mode
Posted by Imre Deak 3 weeks, 2 days ago 
On Fri, Nov 01, 2024 at 11:22:13AM +0200, Jani Nikula wrote:
> On Thu, 31 Oct 2024, Imre Deak <imre.deak@intel.com> wrote:
> > On Thu, Oct 31, 2024 at 05:12:45PM +0200, Abel Vesa wrote:
> >> According to the DisplayPort standard, LTTPRs have two operating
> >> modes:
> >>  - non-transparent - it replies to DPCD LTTPR field specific AUX
> >>    requests, while passes through all other AUX requests
> >>  - transparent - it passes through all AUX requests.
> >> 
> >> Switching between this two modes is done by the DPTX by issuing
> >> an AUX write to the DPCD PHY_REPEATER_MODE register.
> >> 
> >> Add a generic helper that allows switching between these modes.
> >> 
> >> Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
> >> ---
> >>  drivers/gpu/drm/display/drm_dp_helper.c | 17 +++++++++++++++++
> >>  include/drm/display/drm_dp_helper.h     |  1 +
> >>  2 files changed, 18 insertions(+)
> >> 
> >> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> >> index 6ee51003de3ce616c3a52653c2f1979ad7658e21..38d612345986ad54b42228902ea718a089d169c4 100644
> >> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> >> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> >> @@ -2694,6 +2694,23 @@ int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE])
> >>  }
> >>  EXPORT_SYMBOL(drm_dp_lttpr_max_link_rate);
> >>  
> >> +/**
> >> + * drm_dp_lttpr_set_transparent_mode - set the LTTPR in transparent mode
> >> + * @aux: DisplayPort AUX channel
> >> + * @enable: Enable or disable transparent mode
> >> + *
> >> + * Returns 0 on success or a negative error code on failure.
> >
> > Should be "Returns 1 on success".
> 
> But is that a sensible return value?

It matches what the function returns, but yes, would make more sense to
fix the return value instead to be 0 in case of success.

> >
> >> + */
> >> +
> 
> Superfluous newline.
> 
> >> +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable)
> >> +{
> >> +	u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT :
> >> +			  DP_PHY_REPEATER_MODE_NON_TRANSPARENT;
> >> +
> >> +	return drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE, val);
> >> +}
> >> +EXPORT_SYMBOL(drm_dp_lttpr_set_transparent_mode);
> >> +
> >>  /**
> >>   * drm_dp_lttpr_max_lane_count - get the maximum lane count supported by all LTTPRs
> >>   * @caps: LTTPR common capabilities
> >> diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
> >> index 279624833ea9259809428162f4e845654359f8c9..8821ab2d36b0e04d38ccbdddcb703b34de7ed680 100644
> >> --- a/include/drm/display/drm_dp_helper.h
> >> +++ b/include/drm/display/drm_dp_helper.h
> >> @@ -625,6 +625,7 @@ int drm_dp_read_lttpr_phy_caps(struct drm_dp_aux *aux,
> >>  			       u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
> >>  int drm_dp_lttpr_count(const u8 cap[DP_LTTPR_COMMON_CAP_SIZE]);
> >>  int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
> >> +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable);
> >>  int drm_dp_lttpr_max_lane_count(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
> >>  bool drm_dp_lttpr_voltage_swing_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
> >>  bool drm_dp_lttpr_pre_emphasis_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
> >> 
> >> -- 
> >> 2.34.1
> >> 
> 
> -- 
> Jani Nikula, Intel
Re: [PATCH RFC 1/4] drm/dp: Add helper to set LTTPRs in transparent mode
Posted by Dmitry Baryshkov 3 weeks, 2 days ago 
On Fri, Nov 01, 2024 at 03:43:40PM +0200, Imre Deak wrote:
> On Fri, Nov 01, 2024 at 11:22:13AM +0200, Jani Nikula wrote:
> > On Thu, 31 Oct 2024, Imre Deak <imre.deak@intel.com> wrote:
> > > On Thu, Oct 31, 2024 at 05:12:45PM +0200, Abel Vesa wrote:
> > >> According to the DisplayPort standard, LTTPRs have two operating
> > >> modes:
> > >>  - non-transparent - it replies to DPCD LTTPR field specific AUX
> > >>    requests, while passes through all other AUX requests
> > >>  - transparent - it passes through all AUX requests.
> > >> 
> > >> Switching between this two modes is done by the DPTX by issuing
> > >> an AUX write to the DPCD PHY_REPEATER_MODE register.
> > >> 
> > >> Add a generic helper that allows switching between these modes.
> > >> 
> > >> Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
> > >> ---
> > >>  drivers/gpu/drm/display/drm_dp_helper.c | 17 +++++++++++++++++
> > >>  include/drm/display/drm_dp_helper.h     |  1 +
> > >>  2 files changed, 18 insertions(+)
> > >> 
> > >> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> > >> index 6ee51003de3ce616c3a52653c2f1979ad7658e21..38d612345986ad54b42228902ea718a089d169c4 100644
> > >> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> > >> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> > >> @@ -2694,6 +2694,23 @@ int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE])
> > >>  }
> > >>  EXPORT_SYMBOL(drm_dp_lttpr_max_link_rate);
> > >>  
> > >> +/**
> > >> + * drm_dp_lttpr_set_transparent_mode - set the LTTPR in transparent mode
> > >> + * @aux: DisplayPort AUX channel
> > >> + * @enable: Enable or disable transparent mode
> > >> + *
> > >> + * Returns 0 on success or a negative error code on failure.
> > >
> > > Should be "Returns 1 on success".
> > 
> > But is that a sensible return value?
> 
> It matches what the function returns, but yes, would make more sense to
> fix the return value instead to be 0 in case of success.

I think returning 0 is better in case of this function.

> 
> > >
> > >> + */
> > >> +
> > 
> > Superfluous newline.
> > 
> > >> +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable)
> > >> +{
> > >> +	u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT :
> > >> +			  DP_PHY_REPEATER_MODE_NON_TRANSPARENT;
> > >> +
> > >> +	return drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE, val);
> > >> +}
> > >> +EXPORT_SYMBOL(drm_dp_lttpr_set_transparent_mode);
> > >> +
> > >>  /**
> > >>   * drm_dp_lttpr_max_lane_count - get the maximum lane count supported by all LTTPRs
> > >>   * @caps: LTTPR common capabilities
> > >> diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
> > >> index 279624833ea9259809428162f4e845654359f8c9..8821ab2d36b0e04d38ccbdddcb703b34de7ed680 100644
> > >> --- a/include/drm/display/drm_dp_helper.h
> > >> +++ b/include/drm/display/drm_dp_helper.h
> > >> @@ -625,6 +625,7 @@ int drm_dp_read_lttpr_phy_caps(struct drm_dp_aux *aux,
> > >>  			       u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
> > >>  int drm_dp_lttpr_count(const u8 cap[DP_LTTPR_COMMON_CAP_SIZE]);
> > >>  int drm_dp_lttpr_max_link_rate(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
> > >> +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable);
> > >>  int drm_dp_lttpr_max_lane_count(const u8 caps[DP_LTTPR_COMMON_CAP_SIZE]);
> > >>  bool drm_dp_lttpr_voltage_swing_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
> > >>  bool drm_dp_lttpr_pre_emphasis_level_3_supported(const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);
> > >> 
> > >> -- 
> > >> 2.34.1
> > >> 
> > 
> > -- 
> > Jani Nikula, Intel

-- 
With best wishes
Dmitry

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