Re: [PATCH 3/3] drm/i915: Updating the CPU_TRANSCODER for BXT DSI

[Jani Nikula <jani.nikula@intel.com>]

On Thu, 11 Feb 2016, Ramalingam C <ramalingam.c@intel.com> wrote:
> In case of BXT DSI we are updating the CPU_TRANSCODER
> with appropriate value.
>
> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
> Signed-off-by: Uma Shankar <uma.shankar@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h      |    2 ++
>  drivers/gpu/drm/i915/intel_display.c |    5 +++++
>  2 files changed, 7 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 65a2cd0..ef4b376 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -122,6 +122,8 @@ enum transcoder {
>  	TRANSCODER_B,
>  	TRANSCODER_C,
>  	TRANSCODER_EDP,
> +	TRANSCODER_MIPI_A,
> +	TRANSCODER_MIPI_C,
>  	I915_MAX_TRANSCODERS
>  };
>  #define transcoder_name(t) ((t) + 'A')
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index e47a75c..9715056 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -7851,6 +7851,11 @@ static void intel_get_dsi_pipe_timings(struct intel_crtc *crtc,
>  				enc_to_intel_dsi(&encoder->base);
>  			pipe_config->pipe_bpp =
>  				dsi_pixel_format_bpp(intel_dsi->pixel_format);
> +
> +			if (intel_dsi->ports & (1 << PORT_A))
> +				pipe_config->cpu_transcoder = TRANSCODER_MIPI_A;
> +			else
> +				pipe_config->cpu_transcoder = TRANSCODER_MIPI_C;
>  		}
>  	}

As I've said in my review of the previous version of the patch [1], you
can't just add transcoder identifiers and expect everything to magically
work.

The current assumption is there are at most transcoders A, B, C, and
eDP. We use them to index registers. Not all registers have a
corresponding DSI transcoder variant, and if they do, they are not
uniformly spread in the register offset space. See haswell_crtc_disable
for an example where things go wrong. There are others.

I do not know what the best approach here would be; it is obvious to me
this can't work.

BR,
Jani.


[1] http://mid.gmane.org/87powceh4r.fsf@intel.com



-- 
Jani Nikula, Intel Open Source Technology Center
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