Re: [PATCH v2 07/12] drm/rockchip: dw_dp: Implement out-of-band HPD handling

[Chaoyi Chen]

Hi Sebastian,

On 5/1/2026 6:20 AM, Sebastian Reichel wrote:
> Implement out-of-band hotplug handling, which will be used to receive
> external hotplug information from the USB-C state machine. This is
> currently handled by the USBDP PHY, which brings quite some trouble
> as the register being accessed requires the power-domain from the DP
> controller and also requires custom TypeC HPD info parsing in the
> USBDP PHY driver.
> 
> In contrast to the USBDP PHY this does not just enable the hotplug
> signal when a DP AltMode capable adapter is plugged in, but instead
> properly detects if a cable is plugged in for things like USB-C to
> HDMI adapters.
> 
> Signed-off-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>

[...]

> +static void dw_dp_rockchip_hpd_sw_cfg(void *data, bool hpd)
> +{
> +	struct rockchip_dw_dp *dp = data;
> +	u32 hpd_reg = dp->pdata->hpd_reg[dp->id];
> +
> +	dev_dbg(dp->dev, "Force HPD connected=%s\n", str_yes_no(hpd));
> +
> +	dp->hpd_cfg = hpd;
> +
> +	regmap_write(dp->vo_grf, hpd_reg,
> +		     FIELD_PREP_WM16_CONST(ROCKCHIP_VO_GRF_DP_SINK_HPD_CFG, dp->hpd_cfg));

FIELD_PREP_WM16() should be used here because "dp->hpd_cfg" is not a
constant expression.

Other patches in this series have similar issues. Doesn't your compiler
warn you about this? Thanks.

-- 
Best, 
Chaoyi