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

[Jagan Teki <jagan@amarulasolutions.com>]

On Wed, Sep 7, 2022 at 3:34 PM Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
>
> Hi Jagan,
>
> 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.

Jagan.