[PATCH v2 1/2] drm: bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec
Frieder Schrempf
frieder.schrempf at kontron.de
Thu Jul 13 10:01:40 UTC 2023
Hi Tim,
On 13.07.23 09:18, Frieder Schrempf wrote:
> Hi Tim,
>
> On 13.07.23 00:34, Tim Harvey wrote:
>> On Wed, May 3, 2023 at 9:33 AM Frieder Schrempf <frieder at fris.de> wrote:
>>>
>>> From: Frieder Schrempf <frieder.schrempf at kontron.de>
>>>
>>> According to the documentation [1] the proper enable flow is:
>>>
>>> 1. Enable DSI link and keep data lanes in LP-11 (stop state)
>>> 2. Disable stop state to bring data lanes into HS mode
>>>
>>> Currently we do this all at once within enable(), which doesn't
>>> allow to meet the requirements of some downstream bridges.
>>>
>>> To fix this we now enable the DSI in pre_enable() and force it
>>> into stop state using the FORCE_STOP_STATE bit in the ESCMODE
>>> register until enable() is called where we reset the bit.
>>>
>>> We currently do this only for i.MX8M as Exynos uses a different
>>> init flow where samsung_dsim_init() is called from
>>> samsung_dsim_host_transfer().
>>>
>>> [1] https://docs.kernel.org/gpu/drm-kms-helpers.html#mipi-dsi-bridge-operation
>>>
>>> Signed-off-by: Frieder Schrempf <frieder.schrempf at kontron.de>
>>> ---
>>> Changes for v2:
>>> * Drop RFC
>>> ---
>>> drivers/gpu/drm/bridge/samsung-dsim.c | 25 +++++++++++++++++++++++--
>>> 1 file changed, 23 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
>>> index e0a402a85787..9775779721d9 100644
>>> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
>>> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
>>> @@ -859,6 +859,10 @@ static int samsung_dsim_init_link(struct samsung_dsim *dsi)
>>> reg = samsung_dsim_read(dsi, DSIM_ESCMODE_REG);
>>> reg &= ~DSIM_STOP_STATE_CNT_MASK;
>>> reg |= DSIM_STOP_STATE_CNT(driver_data->reg_values[STOP_STATE_CNT]);
>>> +
>>> + if (!samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type))
>>> + reg |= DSIM_FORCE_STOP_STATE;
>>> +
>>> samsung_dsim_write(dsi, DSIM_ESCMODE_REG, reg);
>>>
>>> reg = DSIM_BTA_TIMEOUT(0xff) | DSIM_LPDR_TIMEOUT(0xffff);
>>> @@ -1340,6 +1344,9 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
>>> ret = samsung_dsim_init(dsi);
>>> if (ret)
>>> return;
>>> +
>>> + samsung_dsim_set_display_mode(dsi);
>>> + samsung_dsim_set_display_enable(dsi, true);
>>> }
>>> }
>>>
>>> @@ -1347,9 +1354,16 @@ static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
>>> struct drm_bridge_state *old_bridge_state)
>>> {
>>> struct samsung_dsim *dsi = bridge_to_dsi(bridge);
>>> + u32 reg;
>>>
>>> - samsung_dsim_set_display_mode(dsi);
>>> - samsung_dsim_set_display_enable(dsi, true);
>>> + if (samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type)) {
>>> + samsung_dsim_set_display_mode(dsi);
>>> + samsung_dsim_set_display_enable(dsi, true);
>>> + } else {
>>> + reg = samsung_dsim_read(dsi, DSIM_ESCMODE_REG);
>>> + reg &= ~DSIM_FORCE_STOP_STATE;
>>> + samsung_dsim_write(dsi, DSIM_ESCMODE_REG, reg);
>>> + }
>>>
>>> dsi->state |= DSIM_STATE_VIDOUT_AVAILABLE;
>>> }
>>> @@ -1358,10 +1372,17 @@ static void samsung_dsim_atomic_disable(struct drm_bridge *bridge,
>>> struct drm_bridge_state *old_bridge_state)
>>> {
>>> struct samsung_dsim *dsi = bridge_to_dsi(bridge);
>>> + u32 reg;
>>>
>>> if (!(dsi->state & DSIM_STATE_ENABLED))
>>> return;
>>>
>>> + if (!samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type)) {
>>> + reg = samsung_dsim_read(dsi, DSIM_ESCMODE_REG);
>>> + reg |= DSIM_FORCE_STOP_STATE;
>>> + samsung_dsim_write(dsi, DSIM_ESCMODE_REG, reg);
>>> + }
>>> +
>>> dsi->state &= ~DSIM_STATE_VIDOUT_AVAILABLE;
>>> }
>>>
>>> --
>>> 2.40.0
>>>
>>
>> Hi Frieder,
>>
>> I found this patch to break mipi-dsi display on my board which has:
>> - FocalTech FT5406 10pt touch controller (with no interrupt)
>> - Powertip PH800480T013-IDF02 compatible panel
>> - Toshiba TC358762 compatible DSI to DBI bridge
>> - ATTINY based regulator used for backlight controller and panel enable
>>
>> I enable this via a dt overlay in a pending patch
>> imx8mm-venice-gw72xx-0x-rpidsi.dtso [1] which works on 6.4 but not
>> 6.5-rc1 which has this patch.
>>
>> The issue appears as:
>> [ 6.110585] samsung-dsim 32e60000.dsi: xfer timed out: 29 06 00 00
>> 64 01 05 00 00 00
>> [ 6.326588] tc358762 32e60000.dsi.0: error initializing bridge (-110)
>>
>> Instead of
>> [ 1.011729] samsung-dsim 32e10000.dsi: supply vddcore not found,
>> using dummy regulator
>> [ 1.019829] samsung-dsim 32e10000.dsi: supply vddio not found,
>> using dummy regulator
>> [ 5.649928] samsung-dsim 32e10000.dsi:
>> [drm:samsung_dsim_host_attach] Attached tc358762 device
>>
>> I'm curious what board/panel were you needing this for and do you have
>> any ideas why it broke my setup?
>>
>> I'm also curious what board/panel Alexander tested this with and if
>> Adam or Jagan (or others) have tested this with their hardware?
>
> Sorry for breaking your setup. My test- and use-case is the same as
> Alexander's. I have the SN65DSI84 downstream bridge and without this
> patch it fails to come up in some cases.
>
> The failure is probably related to your downstream bridge being
> controlled by the DSI itself using command mode. The SN65DSI84 is
> instead controlled via I2C.
>
> Actually we should have tested this with a bridge that uses command mode
> before merging, now that I think of it. But I wasn't really aware of
> this until now.
>
> I'll have a closer look at the issue and then will get back to you. In
> the meantime if anyone can help analyze the problem or has proposals how
> to fix it, please let us know.
With my patch samsung_dsim_init() now initializes the DSIM to stop
state. When being called from samsung_dsim_atomic_pre_enable() this
works as the stop state is cleared later in samsung_dsim_atomic_enable().
When being called from samsung_dsim_host_transfer() to handle transfers
before samsung_dsim_atomic_pre_enable() was called, the stop state is
never cleared and transfers will fail.
This is the case in your setup as tc358762_init() is called in
tc358762_pre_enable().
I think that requiring to initialize the DSI host during transfer could
be avoided in this case by moving tc358762_init() from
tc358762_pre_enable() to tc358762_enable().
But at the same time according to the docs at [1] this seems to be a
valid case that we need to support in the DSIM driver:
Whilst it is valid to call host_transfer prior to pre_enable or
after post_disable, the exact state of the lanes is undefined at
this point. The DSI host should initialise the interface, transmit
the data, and then disable the interface again.
Therefore I would propose to try a fix like in the attachement. If you
could test this, that would be great.
Thanks
Frieder
[1]
https://docs.kernel.org/gpu/drm-kms-helpers.html#mipi-dsi-bridge-operation
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