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

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hi Jagan,

On 13.09.2022 19:29, Jagan Teki wrote:
> On Wed, Sep 7, 2022 at 3:34 PM Marek Szyprowski
> <m.szyprowski@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@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.

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