[PATCH v7 2/6] drm/mediatek: dsi: Improves the DSI lane setup robustness
Alexandre Mergnat
amergnat at baylibre.com
Mon Feb 17 07:03:20 PST 2025
Hi CK.
On 17/02/2025 08:56, CK Hu (胡俊光) wrote:
> On Fri, 2025-01-10 at 14:31 +0100, Alexandre Mergnat wrote:
>> External email : Please do not click links or open attachments until you have verified the sender or the content.
>>
>>
>> Currently, mtk_dsi_lane_ready (which setup the DSI lane) is triggered
>> before mtk_dsi_poweron. lanes_ready flag toggle to true during
>> mtk_dsi_lane_ready function, and the DSI module is set up during
>> mtk_dsi_poweron.
>>
>> Later, during panel driver init, mtk_dsi_lane_ready is triggered but does
>> nothing because lanes are considered ready. Unfortunately, when the panel
>> driver try to communicate, the DSI returns a timeout.
>>
>> The solution found here is to put lanes_ready flag to false after the DSI
>> module setup into mtk_dsi_poweron to init the DSI lanes after the power /
>> setup of the DSI module.
>
> I'm not clear about what happen.
> I think this DSI flow has worked for a long time.
> So only some panel has problem?
I don't know if it's related to a specific panel or not.
>
> And another question.
> Do you mean mtk_dsi_lane_ready() do some setting to hardware, but lane is not actually ready?
The workflow should be:
... | dsi->lanes_ready = false | Power-on | setup dsi lanes | dsi->lanes_ready = true (to avoid
re-do dsi lanes setup) | ...
I observe (print function name called + dsi->lanes_ready value):
[ 9.086030] mtk_dsi_probe 0
[ 9.662319] mtk_dsi_host_attach 0
[ 9.662941] mtk_dsi_encoder_init
[ 9.984685] mtk_dsi_poweron 0
[ 10.043755] mtk_dsi_host_transfer 0
[ 10.043769] mtk_dsi_lane_ready 0
[ 10.055837] mtk_dsi_host_transfer 1
[ 10.055853] mtk_dsi_lane_ready 1
[ 10.179788] mtk_dsi_host_transfer 1
[ 10.179803] mtk_dsi_lane_ready 1
[ 10.179880] mtk_dsi_host_transfer 1
[ 10.179885] mtk_dsi_lane_ready 1
[ 10.179920] mtk_dsi_host_transfer 1
[ 10.179923] mtk_dsi_lane_ready 1
[ 10.179986] mtk_dsi_host_transfer 1
[ 10.179993] mtk_dsi_lane_ready 1
[ 10.180134] mtk_dsi_host_transfer 1
[ 10.180143] mtk_dsi_lane_ready 1
[ 10.180175] mtk_dsi_host_transfer 1
[ 10.180178] mtk_dsi_lane_ready 1
[ 10.180223] mtk_dsi_host_transfer 1
[ 10.180226] mtk_dsi_lane_ready 1
[ 10.180245] mtk_dsi_host_transfer 1
[ 10.180248] mtk_dsi_lane_ready 1
[ 10.180278] mtk_dsi_host_transfer 1
[ 10.180280] mtk_dsi_lane_ready 1
[ 10.180312] mtk_dsi_host_transfer 1
[ 10.180314] mtk_dsi_lane_ready 1
[ 10.203774] mtk_dsi_bridge_atomic_pre_enable
[ 10.203787] mtk_dsi_poweron 1
[ 10.203793] mtk_output_dsi_enable
[ 10.203795] mtk_dsi_lane_ready 1
[ 10.471517] mtk_dsi_host_transfer 1
[ 10.486962] mtk_dsi_lane_ready 1
[ 10.487244] mtk_dsi_host_transfer 1
[ 10.503733] mtk_dsi_lane_ready 1
Here the mtk_dsi_lane_ready function:
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 */
}
}
As you can see, something call "mtk_dsi_bridge_atomic_pre_enable" then mtk_dsi_poweron is called a
second time. This issue is probably due to the probe order (race condition).
After all, IMHO, after a poweron, the registers status should be consider as unknown (or at least HW
default value), so, lanes setup has to be done. This solution improve the driver's robustness.
> Or mtk_dsi_lane_ready() configure the hardware and lane is is actually ready,
> but something make it not ready again, what's the thing which break lane ready?
>
> If this is a bug fix, add Fixes tag.
>
> Regards,
> CK
>
>>
>> Signed-off-by: Alexandre Mergnat <amergnat at baylibre.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 e61b9bc68e9a..dcf0d93881b5 100644
>> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
>> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
>> @@ -724,6 +724,8 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
>> mtk_dsi_config_vdo_timing(dsi);
>> mtk_dsi_set_interrupt_enable(dsi);
>>
>> + dsi->lanes_ready = false;
>> +
>> return 0;
>> err_disable_engine_clk:
>> clk_disable_unprepare(dsi->engine_clk);
>>
>> --
>> 2.25.1
>>
>
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--
Regards,
Alexandre
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