Re: [PATCH v4, 3/4] drm/mediatek: keep dsi as LP00 before dcs cmds transfer

[xinlei.lee <xinlei.lee@mediatek.com>]

On Tue, 2022-04-12 at 15:43 +0800, Rex-BC Chen wrote:
> On Mon, 2022-04-11 at 11:07 +0200, AngeloGioacchino Del Regno wrote:
> > Il 11/04/22 04:31, xinlei.lee@mediatek.com ha scritto:
> > > From: Jitao Shi <jitao.shi@mediatek.com>
> > > 
> > > To comply with the panel sequence, hold the mipi signal to LP00
> > > before the dcs cmds transmission,
> > > and pull the mipi signal high from LP00 to LP11 until the start
> > > of
> > > the dcs cmds transmission.
> > > The normal panel timing is :
> > > (1) pp1800 DC pull up
> > > (2) avdd & avee AC pull high
> > > (3) lcm_reset pull high -> pull low -> pull high
> > > (4) Pull MIPI signal high (LP11) -> initial code -> send video
> > > data(HS mode)
> > > The power-off sequence is reversed.
> > > If dsi is not in cmd mode, then dsi will pull the mipi signal
> > > high
> > > in the mtk_output_dsi_enable function.
> > > 
> > > Fixes: 2dd8075d2185 ("drm/mediatek: mtk_dsi: Use the
> > > drm_panel_bridge API")
> > > 
> > > Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
> > > Signed-off-by: Xinlei Lee <xinlei.lee@mediatek.com>
> > > ---
> > >   drivers/gpu/drm/mediatek/mtk_dsi.c | 28 +++++++++++++++++++++--
> > > -----
> > >   1 file changed, 21 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > index cf76c53a1af6..9ad6f08c8bfe 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > @@ -203,6 +203,7 @@ struct mtk_dsi {
> > >   	struct mtk_phy_timing phy_timing;
> > >   	int refcount;
> > >   	bool enabled;
> > > +	bool lanes_ready;
> > >   	u32 irq_data;
> > >   	wait_queue_head_t irq_wait_queue;
> > >   	const struct mtk_dsi_driver_data *driver_data;
> > > @@ -654,13 +655,6 @@ static int mtk_dsi_poweron(struct mtk_dsi
> > > *dsi)
> > >   	mtk_dsi_config_vdo_timing(dsi);
> > >   	mtk_dsi_set_interrupt_enable(dsi);
> > >   
> > > -	mtk_dsi_rxtx_control(dsi);
> > > -	usleep_range(30, 100);
> > > -	mtk_dsi_reset_dphy(dsi);
> > > -	mtk_dsi_clk_ulp_mode_leave(dsi);
> > > -	mtk_dsi_lane0_ulp_mode_leave(dsi);
> > > -	mtk_dsi_clk_hs_mode(dsi, 0);
> > > -
> > >   	return 0;
> > >   err_disable_engine_clk:
> > >   	clk_disable_unprepare(dsi->engine_clk);
> > > @@ -689,6 +683,23 @@ static void mtk_dsi_poweroff(struct mtk_dsi
> > > *dsi)
> > >   	clk_disable_unprepare(dsi->digital_clk);
> > >   
> > >   	phy_power_off(dsi->phy);
> > > +
> > > +	dsi->lanes_ready = false;
> > > +}
> > > +
> > > +static void mtk_dsi_lane_ready(struct mtk_dsi *dsi)
> > > +{
> > > +	if (!dsi->lanes_ready) {
> > > +		dsi->lanes_ready = true;
> > > +		mtk_dsi_rxtx_control(dsi);
> > > +		usleep_range(30, 100);
> > > +		mtk_dsi_reset_dphy(dsi);
> > > +		mtk_dsi_clk_ulp_mode_leave(dsi);
> > > +		mtk_dsi_lane0_ulp_mode_leave(dsi);
> > > +		mtk_dsi_clk_hs_mode(dsi, 0);
> > > +		msleep(20);
> > 
> > This is a very long sleep, which wasn't present before this change.
> > Please document the reasons why we need this 20ms sleep with a
> > comment
> > in the code.
> > 
> > Regards,
> > Angelo
> > 
> > 
> 
> Hello Xinlei,
> 
> As Angelo mentioned.
> I think you should add this in commit message and driver comments.
> (Your reply in v3.)
> "The 20ms delay in mtk_dsi_lane_ready() is because dsi needs to give
> dsi_rx(panel) a reaction time after pulling up the mipi signal."
> 
> BRs,
> Rex
> 

Hey Rex:

Thanks for your review and reminder.
I will add this explanation in the next edition of code & comments.

Best Regards!
xinlei
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