[PATCH v4 02/12] drm: bridge: Add Samsung DSIM bridge driver

[Marek Szyprowski]

Hi Jagan,

On 14.09.2022 11:39, Jagan Teki wrote:
> On Wed, Sep 14, 2022 at 2:51 PM Marek Szyprowski
> <m.szyprowski at samsung.com> wrote:
>> On 13.09.2022 19:29, Jagan Teki wrote:
>>> On Wed, Sep 7, 2022 at 3:34 PM Marek Szyprowski
>>> <m.szyprowski at samsung.com> wrote:
>>>> On 06.09.2022 21:07, Jagan Teki wrote:
>>>>> On Mon, Sep 5, 2022 at 4:54 PM Marek Szyprowski
>>>>> <m.szyprowski at samsung.com> wrote:
>>>>>> On 02.09.2022 12:47, Marek Szyprowski wrote:
>>>>>>> On 29.08.2022 20:40, Jagan Teki wrote:
>>>>>>>> Samsung MIPI DSIM controller is common DSI IP that can be used in
>>>>>>>> various
>>>>>>>> SoCs like Exynos, i.MX8M Mini/Nano.
>>>>>>>>
>>>>>>>> In order to access this DSI controller between various platform SoCs,
>>>>>>>> the ideal way to incorporate this in the drm stack is via the drm bridge
>>>>>>>> driver.
>>>>>>>>
>>>>>>>> This patch is trying to differentiate platform-specific and bridge
>>>>>>>> driver
>>>>>>>> code and keep maintaining the exynos_drm_dsi.c code as platform-specific
>>>>>>>> glue code and samsung-dsim.c as a common bridge driver code.
>>>>>>>>
>>>>>>>> - Exynos specific glue code is exynos specific te_irq, host_attach, and
>>>>>>>>       detach code along with conventional component_ops.
>>>>>>>>
>>>>>>>> - Samsung DSIM is a bridge driver which is common across all
>>>>>>>> platforms and
>>>>>>>>       the respective platform-specific glue will initialize at the end
>>>>>>>> of the
>>>>>>>>       probe. The platform-specific operations and other glue calls will
>>>>>>>> invoke
>>>>>>>>       on associate code areas.
>>>>>>>>
>>>>>>>> v4:
>>>>>>>> * include Inki Dae in MAINTAINERS
>>>>>>>> * remove dsi_driver probe in exynos_drm_drv to support multi-arch build
>>>>>>> This breaks Exynos DRM completely as the Exynos DRM driver is not able
>>>>>>> to wait until the DSI driver is probed and registered as component.
>>>>>>>
>>>>>>> I will show how to rework this the way it is done in
>>>>>>> drivers/gpu/drm/exynos/exynos_dp.c and
>>>>>>> drivers/gpu/drm/bridge/analogix/analogix_dp_core.c soon...
>>>>>> I've finally had some time to implement such approach, see
>>>>>> https://protect2.fireeye.com/v1/url?k=c5d024d9-a4ab8e4e-c5d1af96-74fe4860001d-625a8324a9797375&q=1&e=489b94d4-84fb-408e-b679-a8d27acf2930&u=https%3A%2F%2Fgithub.com%2Fmszyprow%2Flinux%2Ftree%2Fv6.0-dsi-v4-reworked
>>>>>>
>>>>>> If you want me to send the patches against your v4 patchset, let me
>>>>>> know, but imho my changes are much more readable after squashing to the
>>>>>> original patches.
>>>>>>
>>>>>> Now the driver is fully multi-arch safe and ready for further
>>>>>> extensions. I've removed the weak functions, reworked the way the
>>>>>> plat_data is used (dropped the patch related to it) and restored
>>>>>> exynos-dsi driver as a part of the Exynos DRM drivers/subsystem. Feel
>>>>>> free to resend the above as v5 after testing on your hardware. At least
>>>>>> it properly works now on all Exynos boards I have, both compiled into
>>>>>> the kernel or as modules.
>>>>> Thanks. I've seen the repo added on top of Dave patches - does it mean
>>>>> these depends on Dave changes as well?
>>>> Yes and no. My rework doesn't change anything with this dependency. It
>>>> comes from my patch "drm: exynos: dsi: Restore proper bridge chain
>>>> order" already included in your series (patch #1). Without it exynos-dsi
>>>> driver hacks the list of bridges to ensure the order of pre_enable calls
>>>> needed for proper operation. This works somehow with DSI panels on my
>>>> test systems, but it has been reported that it doesn't work with a bit
>>>> more complex display pipelines. Only that patch depends on the Dave's
>>>> patches. If you remove it, you would need to adjust the code in the
>>>> exynos_drm_dsi.c and samsung-dsim.c respectively. imho it would be
>>>> better to keep it and merge Dave's patches together with dsi changes, as
>>>> they are the first real client of it.
>>> I think the Dave patches especially "drm/bridge: Introduce
>>> pre_enable_upstream_first to alter bridge init order" seems not 100%
>>> relevant to this series as they affect bridge chain call flow
>>> globally. Having a separate series for that makes sense to me. I'm
>>> sending v5 by excluding those parts.
>> If so then drop the "drm: exynos: dsi: Restore proper bridge chain
>> order" patch and adjust code respectively in samsung-dsim.c. Without the
>> Dave's patches, that one doesn't make sense.
> Doesn't it break Exynos?

No it won't. Lack of the "drm: exynos: dsi: Restore proper bridge chain 
order" patch doesn't change much against the current state of the driver.

Here is my rework of your v4 patchset without the mentioned patch and 
Dave's patches:

https://github.com/mszyprow/linux/tree/v6.0-dsi-v4-reworked-minimal

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland