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

[Marek Szyprowski]

Hi Jagan,

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.

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