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

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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




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