Re: [PATCH] drm/mediatek: mtk_dsi: enable hs clock during pre-enable

[Gary Bisson <bisson.gary@gmail.com>]

Hi,

On Thu, Jun 18, 2026 at 04:06:28PM -0500, Adam Thiede wrote:
> On 1/20/26 05:36, Gary Bisson wrote:
> > Some bridges, such as the TI SN65DSI83, require the HS clock to be
> > running in order to lock its PLL during its own pre-enable function.
> > 
> > Without this change, the bridge gives the following error:
> > sn65dsi83 14-002c: failed to lock PLL, ret=-110
> > sn65dsi83 14-002c: Unexpected link status 0x01
> > sn65dsi83 14-002c: reset the pipe
> > 
> > Move the necessary functions from enable to pre-enable.
> > 
> > Signed-off-by: Gary Bisson <bisson.gary@gmail.com>
> > ---
> > Tested on Tungsten510 module with sn65dsi83 + tm070jdhg30 panel.
> > 
> > Left mtk_dsi_set_mode() as part of the enable function to mimic what is
> > done in the Samsung DSIM driver which is known to be working the TI
> > bridge.
> > ---
> >   drivers/gpu/drm/mediatek/mtk_dsi.c | 35 +++++++++++++++++------------------
> >   1 file changed, 17 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > index 0e2bcd5f67b7..b560245d1be9 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > @@ -672,6 +672,21 @@ static s32 mtk_dsi_switch_to_cmd_mode(struct mtk_dsi *dsi, u8 irq_flag, u32 t)
> >   	}
> >   }
> > +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);
> > +		usleep_range(1000, 3000);
> > +		/* The reaction time after pulling up the mipi signal for dsi_rx */
> > +	}
> > +}
> > +
> >   static int mtk_dsi_poweron(struct mtk_dsi *dsi)
> >   {
> >   	struct device *dev = dsi->host.dev;
> > @@ -724,6 +739,8 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
> >   	mtk_dsi_set_vm_cmd(dsi);
> >   	mtk_dsi_config_vdo_timing(dsi);
> >   	mtk_dsi_set_interrupt_enable(dsi);
> > +	mtk_dsi_lane_ready(dsi);
> > +	mtk_dsi_clk_hs_mode(dsi, 1);
> >   	return 0;
> >   err_disable_engine_clk:
> > @@ -769,30 +786,12 @@ static void mtk_dsi_poweroff(struct mtk_dsi *dsi)
> >   	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);
> > -		usleep_range(1000, 3000);
> > -		/* The reaction time after pulling up the mipi signal for dsi_rx */
> > -	}
> > -}
> > -
> >   static void mtk_output_dsi_enable(struct mtk_dsi *dsi)
> >   {
> >   	if (dsi->enabled)
> >   		return;
> > -	mtk_dsi_lane_ready(dsi);
> >   	mtk_dsi_set_mode(dsi);
> > -	mtk_dsi_clk_hs_mode(dsi, 1);
> > -
> >   	mtk_dsi_start(dsi);
> >   	dsi->enabled = true;
> > 
> > ---
> > base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
> > change-id: 20260120-mtkdsi-29e4c84e7b38
> > 
> > Best regards,
> 
> Hello,
> This commit was part of 7.1 and caused a problem for me.
> I'm running postmarketOS (basically Alpine Linux) on a Lenovo C330
> chromebook with a Mediatek MT8173 processor.
> The problem: when the display on my laptop powers off (via suspend or idle,
> like xset dpms off) the picture does not come back when the display powers
> back on (from resume). The display backlight comes on and brightness is
> adjustable but there is no picture. The only fix is to reboot.
> 
> Reverting this commit and applying it as a patch on top of 7.1 addresses the
> issue for me.
> 
> You can view the config I'm using here:
> https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/8819
> 
> Is there any sort of testing or other debugging info I can provide to help
> address this issue?

Thanks for reporting the issue, could you share some logs? Is the driver
saying anything during resume? Also, what type of panel is used on that
chromebook?

Thanks,
Gary