Re: [Intel-gfx] [RFC PATCH 4/4] drm/i915: Enable voltage swing before enabling DDI_BUF_CTL.

[Ville Syrjälä]

On Wed, Aug 16, 2017 at 01:19:51PM -0700, Rodrigo Vivi wrote:
> Sequences for DisplayPort asks us to
> " Configure voltage swing and related IO settings.
> Refer to DDI Buffer section."
> 
> before "Configure and enable DDI_BUF_CTL"
> 
> On BXT and CNL this means to execute the ddi vswing sequences.
> 
> At this point these sequences calls are getting duplicated for DP
> because they are all called from DP link trainning sequences.
> 
> However this patch is not yet removing it before a futher discussion
> since spec also allows that during link training without disabling
> anything:
> 
> "
> Notes
> Changing voltage swing during link training:
> Change the swing setting following the DDI Buffer section.
> The port does not need to be disabled.
> "
> 
> Cc: Ville Syrjälä 
> Signed-off-by: Rodrigo Vivi 
> ---
>  drivers/gpu/drm/i915/intel_ddi.c | 7 ++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c 
> b/drivers/gpu/drm/i915/intel_ddi.c
> index a6056bb4f801..8ea0368e15b1 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -2133,6 +2133,7 @@ static void intel_ddi_pre_enable_dp(struct 
> intel_encoder *encoder,
>   struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
>   enum port port = intel_ddi_get_encoder_port(encoder);
>   struct intel_digital_port *dig_port = enc_to_dig_port(>base);
> + uint32_t level = intel_ddi_dp_level(intel_dp);
>  
>   WARN_ON(link_mst && (port == PORT_A || port == PORT_E));
>  
> @@ -2145,7 +2146,11 @@ static void intel_ddi_pre_enable_dp(struct 
> intel_encoder *encoder,
>  
>   intel_display_power_get(dev_priv, dig_port->ddi_io_power_domain);
>  
> - if (!IS_GEN9_LP(dev_priv) && !IS_CANNONLAKE(dev_priv))
> + if (IS_CANNONLAKE(dev_priv))
> + cnl_ddi_vswing_sequence(encoder, level);
> + else if (IS_GEN9_LP(dev_priv))
> + bxt_ddi_vswing_sequence(dev_priv, level, port, encoder->type);

Hmm. Yeah, I guess it would make sense to set these up already before we
enable DDI_BUF_CTL, which I think would happend from the
.prepare_link_retrain() hook on DDI, and that does get called before the
signal levels have been set up.

So I'm fine with this change. Imre, any thoughts?

> + else
>   intel_prepare_dp_ddi_buffers(encoder);
>  
>   intel_ddi_init_dp_buf_reg(encoder);
> -- 
> 2.13.2

-- 
Ville Syrjälä
Intel OTC
___
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

[Intel-gfx] [RFC PATCH 4/4] drm/i915: Enable voltage swing before enabling DDI_BUF_CTL.

[Rodrigo Vivi]

Sequences for DisplayPort asks us to
" Configure voltage swing and related IO settings.
Refer to DDI Buffer section."

before "Configure and enable DDI_BUF_CTL"

On BXT and CNL this means to execute the ddi vswing sequences.

At this point these sequences calls are getting duplicated for DP
because they are all called from DP link trainning sequences.

However this patch is not yet removing it before a futher discussion
since spec also allows that during link training without disabling
anything:

"
Notes
Changing voltage swing during link training:
Change the swing setting following the DDI Buffer section.
The port does not need to be disabled.
"

Cc: Ville Syrjälä 
Signed-off-by: Rodrigo Vivi 
---
 drivers/gpu/drm/i915/intel_ddi.c | 7 ++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index a6056bb4f801..8ea0368e15b1 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -2133,6 +2133,7 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder 
*encoder,
struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
enum port port = intel_ddi_get_encoder_port(encoder);
struct intel_digital_port *dig_port = enc_to_dig_port(>base);
+   uint32_t level = intel_ddi_dp_level(intel_dp);
 
WARN_ON(link_mst && (port == PORT_A || port == PORT_E));
 
@@ -2145,7 +2146,11 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder 
*encoder,
 
intel_display_power_get(dev_priv, dig_port->ddi_io_power_domain);
 
-   if (!IS_GEN9_LP(dev_priv) && !IS_CANNONLAKE(dev_priv))
+   if (IS_CANNONLAKE(dev_priv))
+   cnl_ddi_vswing_sequence(encoder, level);
+   else if (IS_GEN9_LP(dev_priv))
+   bxt_ddi_vswing_sequence(dev_priv, level, port, encoder->type);
+   else
intel_prepare_dp_ddi_buffers(encoder);
 
intel_ddi_init_dp_buf_reg(encoder);
-- 
2.13.2

___
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx