drm/amdkfd: Fix SDMA ring buffer size calculation

[ Upstream commit d12fb13f23199faa7e536acec1db49068e5a067d ]

ffs function return the position of the first bit set on 1 based.
(bit zero returns 1).

Signed-off-by: shaoyun liu <shaoyun.liu@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_cik.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_cik.c
index 44ffd23348fc4481932a851ea6e1d6a38a9b2989..164fa4b1f9a9d7c4305cb69320fe20d4ca858d15 100644 (file)
--- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_cik.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_cik.c
@@ -205,8 +205,8 @@ static int update_mqd_sdma(struct mqd_manager *mm, void *mqd,
        struct cik_sdma_rlc_registers *m;
 
        m = get_sdma_mqd(mqd);
-       m->sdma_rlc_rb_cntl = ffs(q->queue_size / sizeof(unsigned int)) <<
-                       SDMA0_RLC0_RB_CNTL__RB_SIZE__SHIFT |
+       m->sdma_rlc_rb_cntl = (ffs(q->queue_size / sizeof(unsigned int)) - 1)
+                       << SDMA0_RLC0_RB_CNTL__RB_SIZE__SHIFT |
                        q->vmid << SDMA0_RLC0_RB_CNTL__RB_VMID__SHIFT |
                        1 << SDMA0_RLC0_RB_CNTL__RPTR_WRITEBACK_ENABLE__SHIFT |
                        6 << SDMA0_RLC0_RB_CNTL__RPTR_WRITEBACK_TIMER__SHIFT;