Hi Neil
On 8/14/2023 1:01 AM, neil.armstrong@xxxxxxxxxx wrote:
Hi Abhinav,
On 10/08/2023 18:26, Abhinav Kumar wrote:
Hi Neil
On 8/3/2023 10:19 AM, Jessica Zhang wrote:
On 7/31/2023 6:00 AM, Neil Armstrong wrote:
Hi,
On 26/07/2023 00:56, Jessica Zhang wrote:
Due to a recent introduction of the pre_enable_prev_first bridge
flag [1],
the panel driver will be probed before the DSI is enabled, causing the
DCS commands to fail to send.
Ensure that DSI is enabled before panel probe by setting the
prepare_prev_first flag for the panel.
Well this is specific to MSM DSI driver, it's not related at all to
the panel.
I dont fully agree this is a MSM DSI driver specific thing.
If the panel can send its commands in its enable() callback, then this
flag need not be set.
When a panel sends its DCS commands in its pre_enable() callback, any
DSI controller will need to be ON before that otherwise DCS commands
cannot be sent.
With this in mind, may I know why is this a MSM change and not a panel
change?
As per my discussion with Dmitry during the last sync up, we were
aligned on this expectation.
As of today, only the MSM DSI driver expects panels to have
prepare_prev_first because it's the first
one calling pre_enable() before the DSI controller to be on, all other
DSI drivers I know
still enables the DSI controller in mode_set() and thus can send
commands in pre_enable() which
is a loose way to map the pre-video state for DSI panels...
It looks like there are multiple panels already setting this flag so
this panel will not be the first unless they were added to make those
work with MSM (which seems unlikely)
panel-samsung-s6d7aa0.c: ctx->panel.prepare_prev_first = true;
panel-samsung-s6e3ha2.c: ctx->panel.prepare_prev_first = true;
panel-samsung-s6e63j0x03.c: ctx->panel.prepare_prev_first = true;
panel-samsung-s6e8aa0.c: ctx->panel.prepare_prev_first = true;
This is where I would like to understand a bit that if the panel sends
out the ON commands in enable() instead of pre_enable() then, this flag
will not be needed. So its also depends on the panel side and thats why
the bridge feeds of the panel's input in devm_drm_panel_bridge_add_typed()
bridge->pre_enable_prev_first = panel->prepare_prev_first;
A panel driver should not depend on features of a DSI controller, which
is the case here
with this patch. Today's expectation is to send DSI commands in
pre_enable() then when enabled
expect to be in video mode when enable() is called.
We are not depending on any feature as such. Any DSI controller , not
just MSM's would need to be ON for DCS commands to be sent out in the
panel's pre_enable() callback.
Its not true that MSM is the only driver powering on the DSI controller
in pre_enable(). Even MTK seems to be doing that
mtk_dsi_bridge_atomic_pre_enable
So I assume any panel which sends out commands in pre_enable() will not
work with MTK as well.
The main reason is because some DSI controllers cannot send LP commands
after switching
to video mode (allwinner for example), so we must take this into account.
For v6.6, I don't see other solutions than reverting 9e15123eca79
(reverting won't regress anything,
because now it regresses also other panels on MSM platforms) and try to
find a proper solution for v6.7...
No, I would prefer not to revert that. It will bring back special
handling for the parade chip into MSM driver, something which I would
prefer not to go back to. Powering on the DSI in modeset() was done only
for the parade chip.
Neil
Thanks
Abhinav
Hi Neil,
I think there might be some confusion caused by the commit message --
instead of "enabled before panel probe", it should be "enabled before
panel pre_enable()" as the panel on commands are sent during
prepare(), which is matched to bridge pre_enable().
IIRC the general rule is that the panel driver should set the
prepare_prev_first flag if the on commands are sent during
pre_enable(), so I'll keep the code change but correct the commit
message if that's ok with you.
Thanks,
Jessica Zhang
Neil
[1] commit 4fb912e5e190 ("drm/bridge: Introduce
pre_enable_prev_first to alter bridge init order")
It's not the right commit that cause regression here, it's :
9e15123eca79 drm/msm/dsi: Stop unconditionally powering up DSI hosts at
modeset
Fixes: 2349183d32d8 ("drm/panel: add visionox vtdr6130 DSI panel
driver")
Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
---
drivers/gpu/drm/panel/panel-visionox-vtdr6130.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
b/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
index bb0dfd86ea67..e1363e128e7e 100644
--- a/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
+++ b/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
@@ -296,6 +296,7 @@ static int visionox_vtdr6130_probe(struct
mipi_dsi_device *dsi)
dsi->format = MIPI_DSI_FMT_RGB888;
dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
MIPI_DSI_MODE_NO_EOT_PACKET |
MIPI_DSI_CLOCK_NON_CONTINUOUS;
+ ctx->panel.prepare_prev_first = true;
drm_panel_init(&ctx->panel, dev, &visionox_vtdr6130_panel_funcs,
DRM_MODE_CONNECTOR_DSI);
---
base-commit: 28a5c036b05fc5c935cc72d76abd3589825ea9cd
change-id: 20230717-visionox-vtdr-prev-first-e00ae02eec9f
Best regards,
