Subject: Re: [PATCH 5/8] drm/panthor: Minor scheduler refactoring

From: Boris Brezillon <[email-masked]>
Date: Wed, 6 May 2026 12:33:14 +0200

On Tue,  5 May 2026 16:05:11 +0200
Ketil Johnsen <[email-masked]> wrote:

> From: Florent Tomasin <[email-masked]>
> 
> Refactor parts of the group scheduling logic into new helper functions.
> This will simplify addition of the protected mode feature.
> 
> Remove redundant assignments of csg_slot.
> 
> Signed-off-by: Florent Tomasin <[email-masked]>
> Co-developed-by: Ketil Johnsen <[email-masked]>
> Signed-off-by: Ketil Johnsen <[email-masked]>
> ---
>  drivers/gpu/drm/panthor/panthor_sched.c | 135 +++++++++++++++---------
>  1 file changed, 86 insertions(+), 49 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index 5ee386338005c..987072bd867c4 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -1934,6 +1934,12 @@ static void csgs_upd_ctx_init(struct panthor_csg_slots_upd_ctx *ctx)
>  	memset(ctx, 0, sizeof(*ctx));
>  }
>  
> +static void csgs_upd_ctx_ring_doorbell(struct panthor_csg_slots_upd_ctx *ctx,
> +				       u32 csg_id)
> +{
> +	ctx->update_mask |= BIT(csg_id);
> +}
> +
>  static void csgs_upd_ctx_queue_reqs(struct panthor_device *ptdev,
>  				    struct panthor_csg_slots_upd_ctx *ctx,
>  				    u32 csg_id, u32 value, u32 mask)
> @@ -1944,7 +1950,8 @@ static void csgs_upd_ctx_queue_reqs(struct panthor_device *ptdev,
>  
>  	ctx->requests[csg_id].value = (ctx->requests[csg_id].value & ~mask) | (value & mask);
>  	ctx->requests[csg_id].mask |= mask;
> -	ctx->update_mask |= BIT(csg_id);
> +
> +	csgs_upd_ctx_ring_doorbell(ctx, csg_id);
>  }
>  
>  static int csgs_upd_ctx_apply_locked(struct panthor_device *ptdev,
> @@ -1961,8 +1968,12 @@ static int csgs_upd_ctx_apply_locked(struct panthor_device *ptdev,
>  	while (update_slots) {
>  		struct panthor_fw_csg_iface *csg_iface;
>  		u32 csg_id = ffs(update_slots) - 1;
> +		u32 req_mask = ctx->requests[csg_id].mask;
>  
>  		update_slots &= ~BIT(csg_id);
> +		if (!req_mask)
> +			continue;

Looks like something that should be in patch 7, where you update the
doorbell_req register, and then call csgs_upd_ctx_ring_doorbell(),
meaning req_mask can be zero. The other option would be to teach
panthor_csg_slots_upd_ctx about CS doorbells, and let
csgs_upd_ctx_apply_locked() toggle the doorbell_req.

> +
>  		csg_iface = panthor_fw_get_csg_iface(ptdev, csg_id);
>  		panthor_fw_update_reqs(csg_iface, req,
>  				       ctx->requests[csg_id].value,
> @@ -1979,6 +1990,9 @@ static int csgs_upd_ctx_apply_locked(struct panthor_device *ptdev,
>  		int ret;
>  
>  		update_slots &= ~BIT(csg_id);
> +		if (!req_mask)
> +			continue;
> +
>  		csg_iface = panthor_fw_get_csg_iface(ptdev, csg_id);
>  
>  		ret = panthor_fw_csg_wait_acks(ptdev, csg_id, req_mask, &acked, 100);