From 440b5e5d7c7269e79450d441816a69077ed90edf Mon Sep 17 00:00:00 2001
From: Yongqiang Niu <yongqiang.niu@mediatek.com>
Date: Sun, 11 Jul 2021 14:53:51 +0800
Subject: drm/mediatek: Adjust rdma fifo threshold calculate formula
Git-commit: ef668f2790e966c43ff7e13cbedce98ff9da1f7b
Patch-mainline: v5.15-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
The orginal formula will caused rdma fifo threshold config overflow
and no one could come out a solution for all SoC,
set threshold to 70% of max fifo size to make sure it will
not overflow, and 70% is a empirical vlaue.
Signed-off-by: Yongqiang Niu <yongqiang.niu@mediatek.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/mediatek/mtk_disp_rdma.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
index 705f28ceb4dd..75d7f45579e2 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
@@ -162,10 +162,10 @@ void mtk_rdma_config(struct device *dev, unsigned int width,
/*
* Enable FIFO underflow since DSI and DPI can't be blocked.
* Keep the FIFO pseudo size reset default of 8 KiB. Set the
- * output threshold to 6 microseconds with 7/6 overhead to
- * account for blanking, and with a pixel depth of 4 bytes:
+ * output threshold to 70% of max fifo size to make sure the
+ * threhold will not overflow
*/
- threshold = width * height * vrefresh * 4 * 7 / 1000000;
+ threshold = rdma_fifo_size * 7 / 10;
reg = RDMA_FIFO_UNDERFLOW_EN |
RDMA_FIFO_PSEUDO_SIZE(rdma_fifo_size) |
RDMA_OUTPUT_VALID_FIFO_THRESHOLD(threshold);
--
2.38.1