Re: [PATCH v5 6/7] arm64: dts: renesas: sparrow-hawk: Enable DisplayPort by adding DSC

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The rcar_dsc driver ignores the `resets` property from the DT binding, failing to deassert the DSC hardware module's reset state.
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commit a8616c71b764dc9fa4ae244e47795371e7fead44
Author: Marek Vasut <marek.vasut+renesas@mailbox.org>

drm/rcar-du: dsc: Add rudimentary Renesas R-Car V4H DSC driver

This commit introduces a rudimentary DSC bridge driver for the Renesas R-Car
V4H SoC. The driver functions as a pass-through to enable the DSI1 pipeline
and performs VESA DSC encoding.

> diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_dsc.c b/drivers/gpu/drm/renesas/rcar-du/rcar_dsc.c
> new file mode 100644
> index 0000000000000..362e683289d69
> --- /dev/null
> +++ b/drivers/gpu/drm/renesas/rcar-du/rcar_dsc.c

[ ... ]

> +static int rcar_dsc_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct rcar_dsc *dsc;
> +	int ret;
> +
> +	dsc = devm_drm_bridge_alloc(dev, struct rcar_dsc, bridge,
> +				    &rcar_dsc_bridge_ops);
> +	if (IS_ERR(dsc))
> +		return PTR_ERR(dsc);
> +
> +	platform_set_drvdata(pdev, dsc);
> +
> +	dsc->dev = &pdev->dev;
> +
> +	dsc->bridge.next_bridge = of_drm_get_bridge_by_endpoint(dev->of_node,
> +								1, 0);

[Severity: High]
Does this driver fail to retrieve and deassert the DSC module's hardware reset
state?

If the reset control isn't retrieved and deasserted, the DSC hardware module
will remain in a reset state, breaking the display pipeline functionality. It
might coincidentally work if the bootloader has already deasserted the reset,
but could fail on suspend/resume or when the bootloader does not initialize
the display.

Should the driver use devm_reset_control_get_exclusive() here and deassert
the reset state during probe?

> +	if (IS_ERR(dsc->bridge.next_bridge))
> +		return PTR_ERR(dsc->bridge.next_bridge);
> +
> +	dsc->bridge.of_node = dev->of_node;
> +
> +	pm_runtime_enable(&pdev->dev);
> +
> +	ret = devm_drm_bridge_add(dev, &dsc->bridge);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260615-rcar-du-dsc-v5-0-aed1a28610e4@ideasonboard.com?part=6