Re: [PATCH RFC 03/10] drm/panel: Add LGD panel driver for Sony Xperia XZ3

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

On 30/05/2023 00:11, Marijn Suijten wrote:
> On 2023-05-22 04:16:20, Dmitry Baryshkov wrote:
> <snip>
>>> +	if (ctx->dsi->dsc) {
>>
>> dsi->dsc is always set, thus this condition can be dropped.
> 
> I want to leave room for possibly running the panel without DSC (at a
> lower resolution/refresh rate, or at higher power consumption if there
> is enough BW) by not assigning the pointer, if we get access to panel
> documentation: probably one of the magic commands sent in this driver
> controls it but we don't know which.
> 
>>> +		drm_dsc_pps_payload_pack(&pps, ctx->dsi->dsc);
>>> +
>>> +		ret = mipi_dsi_picture_parameter_set(ctx->dsi, &pps);
>>> +		if (ret < 0) {
>>> +			dev_err(panel->dev, "failed to transmit PPS: %d\n", ret);
>>> +			goto fail;
>>> +		}
>>> +		ret = mipi_dsi_compression_mode(ctx->dsi, true);
>>> +		if (ret < 0) {
>>> +			dev_err(dev, "failed to enable compression mode: %d\n", ret);
>>> +			goto fail;
>>> +		}
>>> +
>>> +		msleep(28);
>>> +	}
>>> +
>>> +	ctx->prepared = true;
>>> +	return 0;
>>> +
>>> +fail:
>>> +	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
>>> +	regulator_disable(ctx->vddio);
>>> +	return ret;
>>> +}
> <snip>
>>> +	/* This panel only supports DSC; unconditionally enable it */
> 
> On that note I should perhaps reword this.
> 
>>> +	dsi->dsc = dsc = devm_kzalloc(&dsi->dev, sizeof(*dsc), GFP_KERNEL);
>>
>> I think double assignments are frowned upon.
> 
> Ack.
> 
>>
>>> +	if (!dsc)
>>> +		return -ENOMEM;
>>> +
>>> +	dsc->dsc_version_major = 1;
>>> +	dsc->dsc_version_minor = 1;
>>> +
>>> +	dsc->slice_height = 32;
>>> +	dsc->slice_count = 2;
>>> +	// TODO: Get hdisplay from the mode
>>
>> Would you like to fix the TODO?
> 
> I can't unless either migrating to drm_bridge (is that doable?) or
> expand drm_panel.  That's a larger task, but I don't think this driver
> is the right place to track that desire.  Should I drop the comment
> entirely or reword it?

I'd say, reword it, so that it becomes more obvious why this TODO can 
not be fixed at this moment.

> 
>>> +	WARN_ON(1440 % dsc->slice_count);
>>> +	dsc->slice_width = 1440 / dsc->slice_count;
> 
> <snip>
> 
> - Marijn

-- 
With best wishes
Dmitry