Re: [PATCH] drm/panel/panel-sitronix-st7701: Move init sequence from prepare() to enable()
On 29.08.23 16:35, Jagan Teki wrote: On Sun, Aug 27, 2023 at 12:03 AM Mimoja wrote: I appreciate you taking the time to respond! On 26.08.23 17:18, Marek Vasut wrote: On 8/26/23 11:55, Mimoja wrote: "The .prepare() function is typically called before the display controller starts to transmit video data." and "After the display controller has started transmitting video data, it's safe to call the .enable() function." DSI commands are not DSI video, so this should be OK ? You are correct, my commit message is mixing things up here. I wanted to emphasize roughly the thought of "when enable() is called the dsi core is expected to have its clock initialized". Will take note to clarify this if I succeed to make a case for this patch below :) While generally fine this can lead to a fillup of the transmission queue before the transmission is set up on certain dsi bridges. This issue can also be seen on downstream imx8m* kernels. Can you reproduce this with current mainline Linux or linux-next tree ? I recall the display pipeline in the NXP downstream stuff is very different from mainline . You are very much correct. The NXP downstream kernel is completely different from the upstream one and is really a great example to show the issue (code cleaned up for readability): https://github.com/varigit/linux-imx/blob/5.15-2.0.x-imx_var01/drivers/gpu/drm/bridge/sec-dsim.c#L1368 ``` ret = drm_panel_prepare(dsim->panel); if (unlikely(ret)) [...] /* config esc clock, byte clock and etc */ sec_mipi_dsim_config_clkctrl(dsim); ret = drm_panel_enable(dsim->panel); if (unlikely(ret)) [...] ``` Which SoC does have this problem ? Sadly I don't have any SoCs available which would work perfectly with linux-next, let alone are confirmed affected :/ I were able to make my Kingway Panel work (Custom one and so far unsupported by the st7701 driver) with this patch on downstream 5.4 and 5.15 imx8mn as well as on a raspberry pi CM4 with 6.1. However raspberrypi/linux brings SPI support to the st7701 driver which should not affect this but I would just like to document it here. I could not find any success story with st7701 and the rpi on 6.1 online after a short search (and only one reference with 5.10 which seems to me a bit different in a short comparison) but again I can only offer circumstantial evidence. Sorry :/ If I understand correctly, 5.10 and 5.15 Would work as it is if the DSI host calls the panel's prepare and enable directly from encoder enable. Did you check that? No, I fear the downstream NXP driver is not following the correct / expected calling flow which upstream has implemented. After investigating this and the RPi issue I would like to follow Marek's recommendation and simply sunset this change in favor of fixing the downstream issues in the downstream tree(s). This seems to be mainly an issue for vendor-custom downstream host kernels, and while there might be a case of convention where panels don't sent commands in prepare() and only in enable() I don't think this patch should have a future solely to be cherry-picked into downstream kernels, when we can not make a case for current linux/next. After all: It is now on the internet for better or worse for others to pick up if needed. I appreciate you all taking the time to discuss and I will post the enablement code for the Kingway HW-021P0Z002-01 panel I tested this with in a bit. Cheers and thankful regards Mimoja
[PATCH] drm/panel/panel-sitronix-st7701: Move init sequence from prepare() to enable()
The struct drm_panel_funcs are offering a prepare() and an enable()
entrypoint for panels. According to drm/panel.h:
"The .prepare() function is typically called before the display controller
starts to transmit video data."
and
"After the display controller has started transmitting video data, it's safe
to call the .enable() function."
The st7701 driver currently does not respect this, queing DSI control commands
during enable.
While generally fine this can lead to a fillup of the transmission queue before
the transmission is set up on certain dsi bridges.
This issue can also be seen on downstream imx8m* kernels.
By moving the init sequence into the enable function we not only circumvent the
issue
but also properly soft-reset the panel on enable().
Signed-off-by: Mimoja
Cc: Marek Vasut
Cc: Guido Günther
Cc: Jagan Teki
Cc: Laurent Pinchart
Cc: Linus Walleij
Cc: Sam Ravnborg
Cc: Thierry Reding
---
drivers/gpu/drm/panel/panel-sitronix-st7701.c | 14 +++---
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7701.c
b/drivers/gpu/drm/panel/panel-sitronix-st7701.c
index 7eae83aa0ea1..18c5a8d97cc8 100644
--- a/drivers/gpu/drm/panel/panel-sitronix-st7701.c
+++ b/drivers/gpu/drm/panel/panel-sitronix-st7701.c
@@ -439,6 +439,13 @@ static int st7701_prepare(struct drm_panel *panel)
gpiod_set_value(st7701->reset, 1);
msleep(150);
+ return 0;
+}
+
+static int st7701_enable(struct drm_panel *panel)
+{
+ struct st7701 *st7701 = panel_to_st7701(panel);
+
st7701_init_sequence(st7701);
if (st7701->desc->gip_sequence)
@@ -447,13 +454,6 @@ static int st7701_prepare(struct drm_panel *panel)
/* Disable Command2 */
st7701_switch_cmd_bkx(st7701, false, 0);
- return 0;
-}
-
-static int st7701_enable(struct drm_panel *panel)
-{
- struct st7701 *st7701 = panel_to_st7701(panel);
-
ST7701_DSI(st7701, MIPI_DCS_SET_DISPLAY_ON, 0x00);
return 0;
--
2.39.2
Re: [PATCH] drm/panel/panel-sitronix-st7701: Move init sequence from prepare() to enable()
I appreciate you taking the time to respond! On 26.08.23 17:18, Marek Vasut wrote: On 8/26/23 11:55, Mimoja wrote: "The .prepare() function is typically called before the display controller starts to transmit video data." and "After the display controller has started transmitting video data, it's safe to call the .enable() function." DSI commands are not DSI video, so this should be OK ? You are correct, my commit message is mixing things up here. I wanted to emphasize roughly the thought of "when enable() is called the dsi core is expected to have its clock initialized". Will take note to clarify this if I succeed to make a case for this patch below :) While generally fine this can lead to a fillup of the transmission queue before the transmission is set up on certain dsi bridges. This issue can also be seen on downstream imx8m* kernels. Can you reproduce this with current mainline Linux or linux-next tree ? I recall the display pipeline in the NXP downstream stuff is very different from mainline . You are very much correct. The NXP downstream kernel is completely different from the upstream one and is really a great example to show the issue (code cleaned up for readability): https://github.com/varigit/linux-imx/blob/5.15-2.0.x-imx_var01/drivers/gpu/drm/bridge/sec-dsim.c#L1368 ``` ret = drm_panel_prepare(dsim->panel); if (unlikely(ret)) [...] /* config esc clock, byte clock and etc */ sec_mipi_dsim_config_clkctrl(dsim); ret = drm_panel_enable(dsim->panel); if (unlikely(ret)) [...] ``` Which SoC does have this problem ? Sadly I don't have any SoCs available which would work perfectly with linux-next, let alone are confirmed affected :/ I were able to make my Kingway Panel work (Custom one and so far unsupported by the st7701 driver) with this patch on downstream 5.4 and 5.15 imx8mn as well as on a raspberry pi CM4 with 6.1. However raspberrypi/linux brings SPI support to the st7701 driver which should not affect this but I would just like to document it here. I could not find any success story with st7701 and the rpi on 6.1 online after a short search (and only one reference with 5.10 which seems to me a bit different in a short comparison) but again I can only offer circumstantial evidence. Sorry :/ Thank you again ~Mimoja
