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From:   Yongqiang Niu <yongqiang.niu@mediatek.com>
To:     Chun-Kuang Hu <chunkuang.hu@kernel.org>
CC:     Rob Herring <robh+dt@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        Yongqiang Niu <yongqiang.niu@mediatek.com>,
        Fabien Parent <fparent@baylibre.com>,
        Dennis YC Hsieh <dennis-yc.hsieh@mediatek.com>,
        <devicetree@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-mediatek@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <dri-devel@lists.freedesktop.org>,
        <Project_Global_Chrome_Upstream_Group@mediatek.com>,
        Hsin-Yi Wang <hsinyi@chromium.org>
Subject: [PATCH v3] drm/mediatek: adjust rdma fifo threshold calculate formula
Date:   Sun, 11 Jul 2021 14:53:51 +0800
Message-ID: <1625986431-27399-2-git-send-email-yongqiang.niu@mediatek.com>
In-Reply-To: <1625986431-27399-1-git-send-email-yongqiang.niu@mediatek.com>
References: <1625986431-27399-1-git-send-email-yongqiang.niu@mediatek.com>
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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>
---
 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 f123fc0..f1f6a2e 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
@@ -164,10 +164,10 @@ 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);
-- 
1.8.1.1.dirty