On Thu, Jan 28, 2021 at 3:52 PM CK Hu [off-list ref] wrote:

Hi, Hsin-Yi:

On Thu, 2021-01-28 at 15:27 +0800, Hsin-Yi Wang wrote:

quoted

From: Yongqiang Niu <redacted>

This patch add RDMA fifo size error handle
rdma fifo size will not always bigger than the calculated threshold
if that case happened, we need set fifo size as the threshold

Signed-off-by: Yongqiang Niu <redacted>
Signed-off-by: Hsin-Yi Wang <redacted>
---
 drivers/gpu/drm/mediatek/mtk_disp_rdma.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
index b84004394970f..04b9542010b00 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c

@@ -168,6 +168,10 @@ void mtk_rdma_config(struct device *dev, unsigned int width,
       * account for blanking, and with a pixel depth of 4 bytes:
       */
      threshold = width * height * vrefresh * 4 * 7 / 1000000;
+
+     if (threshold > rdma_fifo_size)
+             threshold = rdma_fifo_size;
+

Please see the discussion in [1].

[1]
https://patchwork.kernel.org/project/linux-mediatek/patch/1607591262-21736-6-git-send-email-yongqiang.niu@mediatek.com/

Regards,
CK

Hi CK,

Even if we set threshold to
threshold = RDMA_FIFO_PSEUDO_SIZE(rdma_fifo_size) * width * height *
vrefresh / 2 / MAX_WIDTH / MAX_HEIGHT / MAX_VREFRESH;

I'm not sure what value MAX_WIDTH, MAX_HEIGHT, and MAX_VREFRESH should
set to for each SoC.
Since there's no conclusion yet, I'll drop this patch in the series,
as this seems not an mt8183 specific fix.

quoted

      reg = RDMA_FIFO_UNDERFLOW_EN |
            RDMA_FIFO_PSEUDO_SIZE(rdma_fifo_size) |
            RDMA_OUTPUT_VALID_FIFO_THRESHOLD(threshold);

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