[Intel-gfx] [PATCH v2] drm/i915/display: Set TRANS_DDI_MODE_SELECT to default value when clearing DDI select

[Ville Syrjälä]

On Mon, Feb 03, 2020 at 02:55:49PM -0800, José Roberto de Souza wrote:
> TGL is suffering of timeouts and fifo underruns when disabling
> transcoder in MST mode, this is fixed by set TRANS_DDI_MODE_SELECT to
> 0(HDMI mode) when clearing DDI select.
> 
> Although BSpec disable sequence don't require this step, it is a
> harmless change and it is also done by Windows driver.
> Anyhow HW team was notified about that but it can take some time to
> documentation to be updated.
> 
> A case that always lead to those issues is:
> - do a modeset enabling pipe A and pipe B in the same MST stream
> leaving A as master
> - disable pipe A, promote B as master doing a full modeset in A
> - enable pipe A, changing the master transcoder back to A(doing a
> full modeset in B)
> - Pow: underruns and timeouts
> 
> The transcoders involved will only work again when complete disabled
> and their power wells turned off causing a reset in their registers.
> 
> v2: Setting TRANS_DDI_MODE_SELECT to default when clearing DDI select
> not anymore when disabling TRANS_DDI, both work but this one looks
> more safe. (Ville comment)

I presume this still fixes the issue?

> 
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index aa066fb9eb00..45082e71262c 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -1988,10 +1988,12 @@ void intel_ddi_disable_transcoder_func(const struct intel_crtc_state *crtc_state
>  	val &= ~TRANS_DDI_FUNC_ENABLE;
>  
>  	if (INTEL_GEN(dev_priv) >= 12) {
> -		if (!intel_dp_mst_is_master_trans(crtc_state))
> +		if (!intel_dp_mst_is_master_trans(crtc_state)) {
>  			val &= ~TGL_TRANS_DDI_PORT_MASK;
> +			val &= ~TRANS_DDI_MODE_SELECT_MASK;

Two separate statements.

> +		}
>  	} else {
> -		val &= ~TRANS_DDI_PORT_MASK;
> +		val &= ~(TRANS_DDI_PORT_MASK | TRANS_DDI_MODE_SELECT_MASK);

One statement.

>  	}
>  	intel_de_write(dev_priv, TRANS_DDI_FUNC_CTL(cpu_transcoder), val);
>  
> @@ -3729,6 +3731,7 @@ static void intel_ddi_post_disable_dp(struct intel_encoder *encoder,
>  			val = intel_de_read(dev_priv,
>  					    TRANS_DDI_FUNC_CTL(cpu_transcoder));
>  			val &= ~TGL_TRANS_DDI_PORT_MASK;
> +			val &= ~TRANS_DDI_MODE_SELECT_MASK;

Two again.

A bit inconsistent, otherwise lgtm.

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

>  			intel_de_write(dev_priv,
>  				       TRANS_DDI_FUNC_CTL(cpu_transcoder),
>  				       val);
> -- 
> 2.25.0

-- 
Ville Syrjälä
Intel