[PATCH] drm/amdkfd: fix the wrong no space return while acquires packet buffer

[Pan, Xinhui]

> 2020年3月19日 18:51，Huang Rui <ray.huang at amd.com> 写道：
> 
> The queue buffer index starts from position 0, so the available buffer size
> which starts from position 0 to rptr should be "rptr" index value. While the
> packet_size_in_dwords == rptr, the available buffer is just good enough.
> 
> Signed-off-by: Huang Rui <ray.huang at amd.com>
> ---
> drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c b/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
> index bae7064..4667c8f 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
> @@ -263,7 +263,7 @@ int kq_acquire_packet_buffer(struct kernel_queue *kq,
> 		/* make sure after rolling back to position 0, there is
> 		 * still enough space.
> 		 */
> -		if (packet_size_in_dwords >= rptr)
> +		if (packet_size_in_dwords > rptr)

rptr should always be > wptr unless ring is empty.

say, rptr is 4, packet_size_in_dwords is 4. Then wptr changes from 0 to 4, that is illegal.


> 			goto err_no_space;
> 
> 		/* fill nops, roll back and start at position 0 */
> -- 
> 2.7.4
> 
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