[Intel-xe] [PATCH 3/4] drm/xe/guc: Fix handling of GUC_HXG_TYPE_NO_RESPONSE_BUSY

[Matthew Brost]

On Wed, Nov 15, 2023 at 12:37:47PM +0100, Michal Wajdeczko wrote:
> If GuC responds with the NO_RESPONSE_BUSY message, we extend
> our timeout while waiting for the actual response, but we wrongly
> assumed that the next message will be RESPONSE_SUCCESS, missing
> that we still can get RESPONSE_FAILURE.
> 
> Change the condition for the expected message type, using only
> common bits from RESPONSE_SUCCESS and RESPONSE_FAILURE (as they
> differ, by ABI design, only by the last bit).
> 
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc.c b/drivers/gpu/drm/xe/xe_guc.c
> index ddbe64eb0f3b..16c233f120c6 100644
> --- a/drivers/gpu/drm/xe/xe_guc.c
> +++ b/drivers/gpu/drm/xe/xe_guc.c
> @@ -671,9 +671,10 @@ int xe_guc_mmio_send_recv(struct xe_guc *guc, const u32 *request,
>  	header = xe_mmio_read32(gt, reply_reg);
>  	if (FIELD_GET(GUC_HXG_MSG_0_TYPE, header) ==
>  	    GUC_HXG_TYPE_NO_RESPONSE_BUSY) {
> +		u32 resp_bits = GUC_HXG_TYPE_RESPONSE_SUCCESS & GUC_HXG_TYPE_RESPONSE_FAILURE;

I think this works but is kinda goofy. It only works because 0x7 & 0x6
are values. If these are defined as 0x6 & 0x1 this doesn't work.

> +		u32 resp_mask = FIELD_PREP(GUC_HXG_MSG_0_TYPE, resp_bits);
>  
> -		ret = xe_mmio_wait32(gt, reply_reg, GUC_HXG_MSG_0_TYPE,
> -				     FIELD_PREP(GUC_HXG_MSG_0_TYPE, GUC_HXG_TYPE_RESPONSE_SUCCESS),
> +		ret = xe_mmio_wait32(gt, reply_reg,  resp_mask, resp_mask,
>  				     1000000, &header, false);
>

Here now we'd need to check for a failure in the header field.

With all of this, I believe it is better just to wait for
GUC_HXG_TYPE_RESPONSE_SUCCESS and have xe_mmio_wait32 timeout on all
other returns. Getting a failure case is rare and we can live a timeout.

Matt

>  		if (unlikely(FIELD_GET(GUC_HXG_MSG_0_ORIGIN, header) !=
> -- 
> 2.25.1
>