Re: [PATCH v6 2/2] usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The Renesas R-Car Gen5 glue register initialization is lost during system suspend and is never restored upon resume.
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commit 83607f1b223c5287acdc795a68974bae2662c342
Author: Thanh Quan <thanh.quan.xn@renesas.com>

usb: dwc3: dwc3-generic-plat: Add Renesas R-Car Gen5 DWC3 xHCI USB controller glue

The Renesas R-Car Gen5 SoC contains multiple instances of DWC3 USB
controller with glue logic wrapper around them. Extend the generic
DWC3 platform driver with Renesas R-Car Gen5 glue logic specifics.

> diff --git a/drivers/usb/dwc3/dwc3-generic-plat.c b/drivers/usb/dwc3/dwc3-generic-plat.c
> index ca69ac0eb07ce..e8586c40d5006 100644
> --- a/drivers/usb/dwc3/dwc3-generic-plat.c
> +++ b/drivers/usb/dwc3/dwc3-generic-plat.c

[ ... ]

> +static int dwc3_renesas_rcar_gen5_init(struct dwc3_generic *dwc3g)
> +{

[ ... ]

> +	/*
> +	 * The datasheet describes initialization procedure without full
> +	 * information about the registers. Therefore, the source code is
> +	 * based on the bare metal code shared by the board team.
> +	 */
> +	writew(0x211, glue + 0x26);
> +
> +	/* USB2 does need additional register programming. */
> +	if (!usb2only)
> +		return 0;
> +
> +	writew(0x11, glue + 0x81c);
> +	writew(0x0, glue + 0x81a);
> +	writew(0x1, glue + 0x802);
> +
> +	usleep_range(10000, 20000);
> +
> +	writew(0x0, glue + 0x802);
> +	writew(0x1, glue + 0x2a);
> +	writew(0x1, glue + 0x81a);

[Severity: High]
Are these glue register settings preserved during a system suspend/resume cycle?

On resume, dwc3_generic_resume() restarts the DWC3 core and reenables clocks,
but it does not provide a mechanism to invoke a platform-specific callback to
restore custom wrapper register writes:

	ret = clk_bulk_prepare_enable(dwc3g->num_clocks, dwc3g->clks);
	if (ret)
		return ret;

	ret = dwc3_pm_resume(dwc);

If the SoC's power domains are powered down during suspend, could the USB
controller operate with uninitialized glue logic after waking up?

Is there a need to add a suspend or resume callback to
struct dwc3_generic_config to ensure the platform-specific initialization
is re-applied?

> +
> +	usleep_range(10000, 20000);
> +
> +	return 0;
> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260828184212.395082-1-marek.vasut+renesas@mailbox.org?part=2