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

[Adam Thiede]

On 6/22/26 06:22, Gary Bisson wrote:
> 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 at 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
The curious thing is that there are no real logs in dmesg or 
/var/log/messages about this. This picture just fails to come back. If 
there are some kernel params I can set to get deeper logging, that would 
help, but I'm not aware of any.

I think the panel is a "BOE NV116WHM-T00" - I used this command to get 
info: cat /sys/class/drm/card0-eDP-1/edid | edid-decode

Output: https://termbin.com/8nbd