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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     shaoyunl <Shaoyun.Liu@amd.com>, shaoyun liu <shaoyun.liu@amd.com>,
        "Felix Kuehling" <Felix.Kuehling@amd.com>,
        Oded Gabbay <oded.gabbay@gmail.com>,
        "Sasha Levin" <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.14 034/100] drm/amdkfd: Fix SDMA ring buffer
 size calculation
Thread-Topic: [PATCH AUTOSEL for 4.14 034/100] drm/amdkfd: Fix SDMA ring
 buffer size calculation
Thread-Index: AQHTlMna6c7eVwegMk2sycA7OOV3sg==
Date:   Wed, 24 Jan 2018 04:14:40 +0000
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From: shaoyunl <Shaoyun.Liu@amd.com>

[ 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@microsoft.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_cik.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

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 44ffd23348fc..164fa4b1f9a9 100644
--- 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;
=20
 	m =3D get_sdma_mqd(mqd);
-	m->sdma_rlc_rb_cntl =3D ffs(q->queue_size / sizeof(unsigned int)) <<
-			SDMA0_RLC0_RB_CNTL__RB_SIZE__SHIFT |
+	m->sdma_rlc_rb_cntl =3D (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;
--=20
2.11.0