Re: [PATCH v1] drm/xe/guc_ct: Assert on credits mismatch during runtime suspend

[Matthew Brost <matthew.brost@intel.com>]

On Tue, Dec 02, 2025 at 02:03:34PM +0530, Raag Jadav wrote:
> G2H credits should be in fully idle state when runtime suspending GuC CT.
> Assert on mismatch.
> 
> Suggested-by: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> Signed-off-by: Raag Jadav <raag.jadav@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_ct.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
> index 2a24d3fb6881..648f0f523abb 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> @@ -253,8 +253,11 @@ static bool g2h_fence_needs_alloc(struct g2h_fence *g2h_fence)
>  #define CTB_DESC_SIZE		ALIGN(sizeof(struct guc_ct_buffer_desc), SZ_2K)
>  #define CTB_H2G_BUFFER_OFFSET	(CTB_DESC_SIZE * 2)
>  #define CTB_H2G_BUFFER_SIZE	(SZ_4K)
> +#define CTB_H2G_BUFFER_DWORDS	(CTB_H2G_BUFFER_SIZE / sizeof(u32))
>  #define CTB_G2H_BUFFER_SIZE	(SZ_128K)
> +#define CTB_G2H_BUFFER_DWORDS	(CTB_G2H_BUFFER_SIZE / sizeof(u32))
>  #define G2H_ROOM_BUFFER_SIZE	(CTB_G2H_BUFFER_SIZE / 2)
> +#define G2H_ROOM_BUFFER_DWORDS	(CTB_G2H_BUFFER_DWORDS / 2)
>  
>  /**
>   * xe_guc_ct_queue_proc_time_jiffies - Return maximum time to process a full
> @@ -403,7 +406,7 @@ int xe_guc_ct_init_post_hwconfig(struct xe_guc_ct *ct)
>  static void guc_ct_ctb_h2g_init(struct xe_device *xe, struct guc_ctb *h2g,
>  				struct iosys_map *map)
>  {
> -	h2g->info.size = CTB_H2G_BUFFER_SIZE / sizeof(u32);
> +	h2g->info.size = CTB_H2G_BUFFER_DWORDS;
>  	h2g->info.resv_space = 0;
>  	h2g->info.tail = 0;
>  	h2g->info.head = 0;
> @@ -421,8 +424,8 @@ static void guc_ct_ctb_h2g_init(struct xe_device *xe, struct guc_ctb *h2g,
>  static void guc_ct_ctb_g2h_init(struct xe_device *xe, struct guc_ctb *g2h,
>  				struct iosys_map *map)
>  {
> -	g2h->info.size = CTB_G2H_BUFFER_SIZE / sizeof(u32);
> -	g2h->info.resv_space = G2H_ROOM_BUFFER_SIZE / sizeof(u32);
> +	g2h->info.size = CTB_G2H_BUFFER_DWORDS;
> +	g2h->info.resv_space = G2H_ROOM_BUFFER_DWORDS;
>  	g2h->info.head = 0;
>  	g2h->info.tail = 0;
>  	g2h->info.space = CIRC_SPACE(g2h->info.tail, g2h->info.head,
> @@ -725,6 +728,12 @@ void xe_guc_ct_stop(struct xe_guc_ct *ct)
>   */
>  void xe_guc_ct_runtime_suspend(struct xe_guc_ct *ct)
>  {
> +	struct guc_ctb *g2h = &ct->ctbs.g2h;
> +	u32 credits = CIRC_SPACE(0, 0, CTB_G2H_BUFFER_DWORDS) - G2H_ROOM_BUFFER_DWORDS;
> +
> +	/* We should be back to guc_ct_ctb_g2h_init() values */
> +	xe_gt_assert(ct_to_gt(ct), g2h->info.space == credits);
> +
>  	/*
>  	 * Since we're already in runtime suspend path, we shouldn't have pending
>  	 * messages. But if there happen to be any, we'd probably want them to be
> -- 
> 2.43.0
>