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

[Chris Zhong]

Hi John

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:
>
> https://patchwork.kernel.org/patch/9340193/
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 
before,
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.

Chris Zhong
> >   		if (tmp < max_mbps)
> >   			target_mbps = tmp;
> >   		else