Il 17/02/25 16:03, Alexandre Mergnat ha scritto:
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:
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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):
Alex, the first poweron is called by mtk_dsi_ddp_start() - and the start callback
is internal to the mediatek-drm driver.
That callback is called by mtk_crtc during setup and during bridge enable(), and
there we go with suboptimal code design backfiring - instead of using what the
DRM APIs provide, this driver uses something custom *and* the DRM APIs, giving
this issue.
Part of what mtk_crtc does is duplicated with what the DRM APIs want to do, so
there you go, that's your problem here :-)
Should I go on with describing the next step(s), or is that obvious for everyone?
:-)
Cheers,
Angelo
[ 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@xxxxxxxxxxxx>
---
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
