Re: [PATCH v6 5/5] drm/v3d: Use V3D_SMS registers for power on/off and reset on V3D 7.x

[Stefan Wahren <wahrenst@gmx.net>]

Hi Maíra,

Am 18.03.25 um 02:01 schrieb Maíra Canal:
> In addition to the standard reset controller, V3D 7.x requires configuring
> the V3D_SMS registers for proper power on/off and reset. Add the new
> registers to `v3d_regs.h` and ensure they are properly configured during
> device probing, removal, and reset.
>
> This change fixes GPU reset issues on the Raspberry Pi 5 (BCM2712).
> Without exposing these registers, a GPU reset causes the GPU to hang,
> stopping any further job execution and freezing the desktop GUI. The same
> issue occurs when unloading and loading the v3d driver.
>
> Link: https://github.com/raspberrypi/linux/issues/6660
> Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
> Signed-off-by: Maíra Canal <mcanal@igalia.com>
> ---
>   drivers/gpu/drm/v3d/v3d_drv.c  | 40 ++++++++++++++++++++++++++++++++++++++++
>   drivers/gpu/drm/v3d/v3d_drv.h  | 11 +++++++++++
>   drivers/gpu/drm/v3d/v3d_gem.c  | 17 +++++++++++++++++
>   drivers/gpu/drm/v3d/v3d_regs.h | 26 ++++++++++++++++++++++++++
>   4 files changed, 94 insertions(+)
>
> diff --git a/drivers/gpu/drm/v3d/v3d_drv.c b/drivers/gpu/drm/v3d/v3d_drv.c
> index c63f0ed1bd8a3d5511085e76ed2fbd6ee7df6f80..122848cdccc4a02039d9ea2e77aa2f377886b5d6 100644
> --- a/drivers/gpu/drm/v3d/v3d_drv.c
> +++ b/drivers/gpu/drm/v3d/v3d_drv.c
> @@ -263,6 +263,36 @@ static const struct of_device_id v3d_of_match[] = {
>   };
>   MODULE_DEVICE_TABLE(of, v3d_of_match);
>
> +static void
> +v3d_idle_sms(struct v3d_dev *v3d)
> +{
> +	if (v3d->ver < V3D_GEN_71)
> +		return;
> +
> +	V3D_SMS_WRITE(V3D_SMS_TEE_CS, V3D_SMS_CLEAR_POWER_OFF);
> +
> +	if (wait_for((V3D_GET_FIELD(V3D_SMS_READ(V3D_SMS_TEE_CS),
> +				    V3D_SMS_STATE) == V3D_SMS_IDLE), 100)) {
> +		DRM_ERROR("Failed to power up SMS\n");
> +	}
> +
> +	v3d_reset_sms(v3d);
> +}
> +
> +static void
> +v3d_power_off_sms(struct v3d_dev *v3d)
> +{
> +	if (v3d->ver < V3D_GEN_71)
> +		return;
> +
> +	V3D_SMS_WRITE(V3D_SMS_TEE_CS, V3D_SMS_POWER_OFF);
> +
> +	if (wait_for((V3D_GET_FIELD(V3D_SMS_READ(V3D_SMS_TEE_CS),
> +				    V3D_SMS_STATE) == V3D_SMS_POWER_OFF_STATE), 100)) {
> +		DRM_ERROR("Failed to power off SMS\n");
> +	}
> +}
> +
>   static int
>   map_regs(struct v3d_dev *v3d, void __iomem **regs, const char *name)
>   {
> @@ -300,6 +330,12 @@ static int v3d_platform_drm_probe(struct platform_device *pdev)
>   	if (ret)
>   		return ret;
>
> +	if (v3d->ver >= V3D_GEN_71) {
> +		ret = map_regs(v3d, &v3d->sms_regs, "sms");
> +		if (ret)
> +			return ret;
Is it correct, that BCM2712 now requires the SMS register and otherwise
the driver doesn't probe?

Just a note for the future: the devicetree is considered as an ABI [1],
so new kernels should still work with old DTB (no regression). For
Raspberry Pi OS, the kernel and DTB are always updated, but this doesn't
apply for Linux Mainline. AFAIK V3D doesn't work with Linux Mainline on
Raspberry Pi 5 yet, so this is just a theoretical problem.

Best regards

[1] - https://docs.kernel.org/devicetree/bindings/ABI.html