[PATCH v3,4/4] drm/mediatek: Add pull-down MIPI operation in mtk_dsi_poweroff function

[Rex-BC Chen]

On Tue, 2022-03-22 at 18:00 +0800, xinlei.lee wrote:
> On Thu, 2022-03-17 at 20:20 +0800, Rex-BC Chen wrote:
> > Hello Xinlei,
> > 
> > On Thu, 2022-03-17 at 15:53 +0800, xinlei.lee at mediatek.com wrote:
> > > From: Xinlei Lee <xinlei.lee at mediatek.com>
> > > 
> > > In the dsi_enable function, mtk_dsi_rxtx_control is to
> > > pull up the MIPI signal operation. Before dsi_disable,
> > > MIPI should also be pulled down by writing a register instead of
> > > disabling dsi.
> > > 
> > 
> > What will happen if you do not pulled down the mipi before disable
> > dsi?
> > What's differnet for this two setting?
> > 
> > > Signed-off-by: Jitao Shi <jitao.shi at mediatek.com>
> > > Signed-off-by: Xinlei Lee <xinlei.lee at mediatek.com>
> > > ---
> > >  drivers/gpu/drm/mediatek/mtk_dsi.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > index b509d59235e2..1c6a75a46b67 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > @@ -676,6 +676,8 @@ static void mtk_dsi_poweroff(struct mtk_dsi
> > > *dsi)
> > >  	mtk_dsi_reset_engine(dsi);
> > >  	mtk_dsi_lane0_ulp_mode_enter(dsi);
> > >  	mtk_dsi_clk_ulp_mode_enter(dsi);
> > > +	/* set the lane number as 0 */

Hello Xinlei,

I think you can write this comment more detailed, like
"/* set the lane number as 0 to pull down mipi */"

> > > +	writel(0, dsi->regs + DSI_TXRX_CTRL);
> > 
> > So set lane num to 0 means pull down mipi?
> > 
> > BRs,
> > Rex
> > 
> > >  
> > >  	mtk_dsi_disable(dsi);
> > >  
> > 
> > 
> 
> Hi rex:
> 
> 1. 
> If you disable dsi without pulling the mipi signal low, the value of
> the register will still maintain the setting of the mipi signal being
> pulled high. 
> After resume, even if the mipi signal is not pulled high, it will
> still
> be in the high state.
> 

I think you can describe this in commit message


BRs,
Rex

> 2.So set lane num to 0 means pull down mipi
> => yes
> 
> Do you have any suggestions on the next version?
> 
> Best Regards!
> xinlei
>