Re: [PATCH v2 11/11] drm/rockchip/dsi: fix insufficient bandwidth of some panel

From: Chris Zhong
Date: Tue Feb 14 2017 - 23:13:15 EST

Hi John

On 01/17/2017 06:54 PM, John Keeping wrote:
On Tue, 17 Jan 2017 17:31:53 +0800, Chris Zhong wrote:

On 01/16/2017 08:44 PM, John Keeping wrote:
On Mon, 16 Jan 2017 18:08:31 +0800, Chris Zhong wrote:
Set the lanes bps to 1 / 0.9 times of pclk, the margin is not enough
for some panel, it will cause the screen display is not normal, so
increases the badnwidth to 1 / 0.8.

Signed-off-by: Chris Zhong <zyw@xxxxxxxxxxxxxx>


drivers/gpu/drm/rockchip/dw-mipi-dsi.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
index 9dfa73d..5a973fe 100644
--- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
@@ -501,8 +501,8 @@ static int dw_mipi_dsi_get_lane_bps(struct dw_mipi_dsi *dsi)
mpclk = DIV_ROUND_UP(dsi->mode->clock, MSEC_PER_SEC);
if (mpclk) {
- /* take 1 / 0.9, since mbps must big than bandwidth of RGB */
- tmp = mpclk * (bpp / dsi->lanes) * 10 / 9;
+ /* take 1 / 0.8, since mbps must big than bandwidth of RGB */
+ tmp = mpclk * (bpp / dsi->lanes) * 10 / 8;
This and patch 9 are just hacking around the underlying problem in order
to make particular panels work. I'm pretty sure the actual issue is the
use of hardcoded values when configuring the PHY, since the PHY
parameters are specified in clock cycles but the MIPI spec requires
absolute time durations.

I posted a series addressing this a while ago, although I screwed up
sending it so some patches were included twice and since no one
expressed any interest I didn't post a cleaned up version.

The relevant patch is here:
Thanks very much, your patches are very useful for me. It looks your
method is correct.
And I am very confused why Mark Yao and me did not receive your patches
although we have subscribed the <linux-rockchip@xxxxxxxxxxxxxxxxxxx>.

In addition, could you tell me which device ware you testing with these
mipi patches.
I going to test them these day.
I'm using RK3288 and I tested my patches with three different MIPI
displays, two of which require commands to be sent in order to set up
the panel.

Thanks for testing the patches.

I think we really need this patch, one mipi panel hit this problem again, with all your 24 patches
and my 6 MIPI DSI patches
So I will update my series to v7, and add this patch into it.