* [PATCH v1] drm/mediatek: fix up 1440x900 dp display black screen issue
@ 2019-11-26 6:47 yongqiang.niu
2019-11-27 1:31 ` CK Hu
0 siblings, 1 reply; 2+ messages in thread
From: yongqiang.niu @ 2019-11-26 6:47 UTC (permalink / raw)
To: CK Hu, Philipp Zabel, Rob Herring, Matthias Brugger
Cc: David Airlie, Daniel Vetter, Mark Rutland, dri-devel, devicetree,
linux-kernel, linux-arm-kernel, linux-mediatek, Yongqiang Niu
From: Yongqiang Niu <yongqiang.niu@mediatek.com>
This patch fix up 1440x900 dp display black screen issue
the computed result will overflow rdma1 fifo max size
when external display pixel clock bigger than 74MHZ
Signed-off-by: Yongqiang Niu <yongqiang.niu@mediatek.com>
---
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 c1abde3..41143f5 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
@@ -152,6 +152,10 @@ static void mtk_rdma_config(struct mtk_ddp_comp *comp, 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;
+
reg = RDMA_FIFO_UNDERFLOW_EN |
RDMA_FIFO_PSEUDO_SIZE(rdma_fifo_size) |
RDMA_OUTPUT_VALID_FIFO_THRESHOLD(threshold);
--
1.8.1.1.dirty
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v1] drm/mediatek: fix up 1440x900 dp display black screen issue
2019-11-26 6:47 [PATCH v1] drm/mediatek: fix up 1440x900 dp display black screen issue yongqiang.niu
@ 2019-11-27 1:31 ` CK Hu
0 siblings, 0 replies; 2+ messages in thread
From: CK Hu @ 2019-11-27 1:31 UTC (permalink / raw)
To: yongqiang.niu
Cc: Philipp Zabel, Rob Herring, Matthias Brugger, David Airlie,
Daniel Vetter, Mark Rutland, dri-devel, devicetree, linux-kernel,
linux-arm-kernel, linux-mediatek
Hi, Yongqiang:
On Tue, 2019-11-26 at 14:47 +0800, yongqiang.niu@mediatek.com wrote:
> From: Yongqiang Niu <yongqiang.niu@mediatek.com>
>
> This patch fix up 1440x900 dp display black screen issue
> the computed result will overflow rdma1 fifo max size
> when external display pixel clock bigger than 74MHZ
>
> Signed-off-by: Yongqiang Niu <yongqiang.niu@mediatek.com>
> ---
> 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 c1abde3..41143f5 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> @@ -152,6 +152,10 @@ static void mtk_rdma_config(struct mtk_ddp_comp *comp, 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;
> +
This looks like that threshold is over spec. I think this FIFO is used
to cover the latency of reading data from DRAM. When data is read from
OVL not RDMA, OVL already has a FIFO, so RDMA FIFO is useless. So I
think you should set threshold to a special value when RDMA is in direct
link mode.
Regards,
CK
> reg = RDMA_FIFO_UNDERFLOW_EN |
> RDMA_FIFO_PSEUDO_SIZE(rdma_fifo_size) |
> RDMA_OUTPUT_VALID_FIFO_THRESHOLD(threshold);
^ permalink raw reply [flat|nested] 2+ messages in thread
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