[PATCH v8 06/14] drm: bridge: samsung-dsim: Handle proper DSI host initialization
Marek Szyprowski
m.szyprowski at samsung.com
Fri Dec 2 10:52:51 UTC 2022
Hi,
Sorry for delay, I was on a sick leave last 2 weeks.
On 28.11.2022 15:43, Jagan Teki wrote:
> ,On Sat, Nov 26, 2022 at 3:44 AM Marek Vasut <marex at denx.de> wrote:
>> On 11/23/22 21:09, Jagan Teki wrote:
>>> On Sat, Nov 19, 2022 at 7:45 PM Marek Vasut <marex at denx.de> wrote:
>>>> On 11/17/22 14:04, Marek Szyprowski wrote:
>>>>> On 17.11.2022 05:58, Marek Vasut wrote:
>>>>>> On 11/10/22 19:38, Jagan Teki wrote:
>>>>>>> DSI host initialization handling in previous exynos dsi driver has
>>>>>>> some pitfalls. It initializes the host during host transfer() hook
>>>>>>> that is indeed not the desired call flow for I2C and any other DSI
>>>>>>> configured downstream bridges.
>>>>>>>
>>>>>>> Host transfer() is usually triggered for downstream DSI panels or
>>>>>>> bridges and I2C-configured-DSI bridges miss these host initialization
>>>>>>> as these downstream bridges use bridge operations hooks like pre_enable,
>>>>>>> and enable in order to initialize or set up the host.
>>>>>>>
>>>>>>> This patch is trying to handle the host init handler to satisfy all
>>>>>>> downstream panels and bridges. Added the DSIM_STATE_REINITIALIZED state
>>>>>>> flag to ensure that host init is also done on first cmd transfer, this
>>>>>>> helps existing DSI panels work on exynos platform (form Marek
>>>>>>> Szyprowski).
>>>>>>>
>>>>>>> v8, v7, v6, v5:
>>>>>>> * none
>>>>>>>
>>>>>>> v4:
>>>>>>> * update init handling to ensure host init done on first cmd transfer
>>>>>>>
>>>>>>> v3:
>>>>>>> * none
>>>>>>>
>>>>>>> v2:
>>>>>>> * check initialized state in samsung_dsim_init
>>>>>>>
>>>>>>> v1:
>>>>>>> * keep DSI init in host transfer
>>>>>>>
>>>>>>> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
>>>>>>> Signed-off-by: Jagan Teki <jagan at amarulasolutions.com>
>>>>>>> ---
>>>>>>> drivers/gpu/drm/bridge/samsung-dsim.c | 25 +++++++++++++++++--------
>>>>>>> include/drm/bridge/samsung-dsim.h | 5 +++--
>>>>>>> 2 files changed, 20 insertions(+), 10 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c
>>>>>>> b/drivers/gpu/drm/bridge/samsung-dsim.c
>>>>>>> index bb1f45fd5a88..ec7e01ae02ea 100644
>>>>>>> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
>>>>>>> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
>>>>>>> @@ -1234,12 +1234,17 @@ static void samsung_dsim_disable_irq(struct
>>>>>>> samsung_dsim *dsi)
>>>>>>> disable_irq(dsi->irq);
>>>>>>> }
>>>>>>> -static int samsung_dsim_init(struct samsung_dsim *dsi)
>>>>>>> +static int samsung_dsim_init(struct samsung_dsim *dsi, unsigned int
>>>>>>> flag)
>>>>>>> {
>>>>>>> const struct samsung_dsim_driver_data *driver_data =
>>>>>>> dsi->driver_data;
>>>>>>> + if (dsi->state & flag)
>>>>>>> + return 0;
>>>>>>> +
>>>>>>> samsung_dsim_reset(dsi);
>>>>>>> - samsung_dsim_enable_irq(dsi);
>>>>>>> +
>>>>>>> + if (!(dsi->state & DSIM_STATE_INITIALIZED))
>>>>>>> + samsung_dsim_enable_irq(dsi);
>>>>>>> if (driver_data->reg_values[RESET_TYPE] == DSIM_FUNCRST)
>>>>>>> samsung_dsim_enable_lane(dsi, BIT(dsi->lanes) - 1);
>>>>>>> @@ -1250,6 +1255,8 @@ static int samsung_dsim_init(struct
>>>>>>> samsung_dsim *dsi)
>>>>>>> samsung_dsim_set_phy_ctrl(dsi);
>>>>>>> samsung_dsim_init_link(dsi);
>>>>>>> + dsi->state |= flag;
>>>>>>> +
>>>>>>> return 0;
>>>>>>> }
>>>>>>> @@ -1269,6 +1276,10 @@ static void
>>>>>>> samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
>>>>>>> }
>>>>>>> dsi->state |= DSIM_STATE_ENABLED;
>>>>>>> +
>>>>>>> + ret = samsung_dsim_init(dsi, DSIM_STATE_INITIALIZED);
>>>>>>> + if (ret)
>>>>>>> + return;
>>>>>>> }
>>>>>>> static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
>>>>>>> @@ -1458,12 +1469,9 @@ static ssize_t
>>>>>>> samsung_dsim_host_transfer(struct mipi_dsi_host *host,
>>>>>>> if (!(dsi->state & DSIM_STATE_ENABLED))
>>>>>>> return -EINVAL;
>>>>>>> - if (!(dsi->state & DSIM_STATE_INITIALIZED)) {
>>>>>>> - ret = samsung_dsim_init(dsi);
>>>>>>> - if (ret)
>>>>>>> - return ret;
>>>>>>> - dsi->state |= DSIM_STATE_INITIALIZED;
>>>>>>> - }
>>>>>>> + ret = samsung_dsim_init(dsi, DSIM_STATE_REINITIALIZED);
>>>>>> This triggers full controller reset and reprogramming upon first
>>>>>> command transfer, is such heavy handed reload really necessary ?
>>>>> Yes it is, otherwise the proper DSI panels doesn't work with Exynos DRM
>>>>> DSI. If this is a real issue for you, then maybe the driver could do the
>>>>> initialization conditionally, in prepare() callback in case of IMX and
>>>>> on the first transfer in case of Exynos?
>>>> That's odd , it does actually break panel support for me, without this
>>>> double reset the panel works again. But I have to wonder, why would such
>>>> a full reset be necessary at all , even on the exynos ?
>>> Is it breaking samsung_dsim_reset from host_transfer? maybe checking
>>> whether a reset is required before calling it might fix the issue. I
>>> agree with double initialization is odd but it seems it is required on
>>> some panels in Exynos, I think tweaking them and adjusting the panel
>>> code might resolve this discrepancy.
>> Can someone provide further details on the exynos problem ?
> If I'm correct this sequence is required in order to work the existing
> panel/bridges on exynos. Adjusting these panel/bridge codes can
> possibly fix the sequence further.
>
> Marek Szyprowski, please add if you have anything.
Well, frankly speaking the double initialization is not a correct
sequence, but this is the only one that actually works on Exynos based
boards with DSI panels after moving the initialization to bridge's
.prepare() callback. I've already explained this and shared the results
of my investigation in my replies to the previous versions of this
patchset. The original Exynos DSI driver does the initialization on the
first DSI command. This however doesn't work for Jagan with I2C
controlled panels/bridges, so he moved the initialization to the
.prepare() callback, what broke the Exynos case (in-short - all tested
panels works fine only if the DSI host initialization is done AFTER
turning the panel's power on). For more information, see this thread:
https://lore.kernel.org/all/e96197f9-948a-997e-5453-9f9d179b5f5a@samsung.com/
Now, the more I think of it, the more I'm convinced that we simply
should add a hack based on the HW type: do the initialization in
.prepare() for non-Exynos case and before the first transfer for the
Exynos case, as there is no way to detect the panel/next bridge type
(I2C or DSI controlled).
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
More information about the dri-devel
mailing list