[PATCH v9 10/18] drm: bridge: samsung-dsim: Init exynos host for first DSI transfer

[Jagan Teki]

On Tue, Dec 13, 2022 at 5:50 PM Marek Szyprowski
<m.szyprowski at samsung.com> wrote:
>
> Hi,
>
> On 13.12.2022 11:40, Jagan Teki wrote:
> > On Tue, Dec 13, 2022 at 2:28 PM Marek Szyprowski
> > <m.szyprowski at samsung.com> wrote:
> >> On 12.12.2022 16:33, Jagan Teki wrote:
> >>
> >> On Mon, Dec 12, 2022 at 8:52 PM Marek Szyprowski
> >> <m.szyprowski at samsung.com> wrote:
> >>
> >> On 12.12.2022 09:43, Marek Szyprowski wrote:
> >>
> >> On 12.12.2022 09:32, Jagan Teki wrote:
> >>
> >> On Mon, Dec 12, 2022 at 1:56 PM Marek Szyprowski
> >> <m.szyprowski at samsung.com> wrote:
> >>
> >> Hi Jagan,
> >>
> >> On 09.12.2022 16:23, Jagan Teki wrote:
> >>
> >> The existing drm panels and bridges in Exynos required host
> >> initialization during the first DSI command transfer even though
> >> the initialization was done before.
> >>
> >> This host reinitialization is handled via DSIM_STATE_REINITIALIZED
> >> flag and triggers from host transfer.
> >>
> >> Do this exclusively for Exynos.
> >>
> >> Initial logic is derived from Marek Szyprowski changes.
> >>
> >> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
> >> Signed-off-by: Jagan Teki <jagan at amarulasolutions.com>
> >> ---
> >> Changes from v9:
> >> - derived from v8
> >> - added comments
> >>
> >>     drivers/gpu/drm/bridge/samsung-dsim.c | 15 ++++++++++++++-
> >>     include/drm/bridge/samsung-dsim.h     |  5 +++--
> >>     2 files changed, 17 insertions(+), 3 deletions(-)
> >>
> >> The following chunk is missing compared to v8:
> >>
> >> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c
> >> b/drivers/gpu/drm/bridge/samsung-dsim.c
> >> index 6e9ad955ebd3..6a9403cb92ae 100644
> >> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> >> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> >> @@ -1315,7 +1315,9 @@ static int samsung_dsim_init(struct samsung_dsim
> >> *dsi, unsigned int flag)
> >>                    return 0;
> >>
> >>            samsung_dsim_reset(dsi);
> >> -       samsung_dsim_enable_irq(dsi);
> >> +
> >> +       if (!(dsi->state & DSIM_STATE_INITIALIZED))
> >> +               samsung_dsim_enable_irq(dsi);
> >>
> >> Is this really required? does it make sure that the IRQ does not
> >> enable twice?
> >>
> >> That's what that check does. Without the 'if (!(dsi->state &
> >> DSIM_STATE_INITIALIZED))' check, the irqs will be enabled twice (first
> >> from pre_enable, then from the first transfer), what leads to a
> >> warning from irq core.
> >>
> >> I've just noticed that we also would need to clear the
> >> DSIM_STATE_REINITIALIZED flag in dsim_suspend.
> >>
> >> However I've found that a bit simpler patch would keep the current code
> >> flow for Exynos instead of this reinitialization hack. This can be
> >> applied on the "[PATCH v9 09/18] drm: bridge: samsung-dsim: Add host
> >> init in pre_enable" patch:
> >>
> >> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c
> >> b/drivers/gpu/drm/bridge/samsung-dsim.c
> >> index 0b2e52585485..acc95c61ae45 100644
> >> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> >> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> >> @@ -1291,9 +1291,11 @@ 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;
> >> +       if (!samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type)) {
> >> +               ret = samsung_dsim_init(dsi, DSIM_STATE_INITIALIZED);
> >> +               if (ret)
> >> +                       return;
> >> +       }
> >>
> >> Sorry, I don't understand this. Does it mean Exynos doesn't need to
> >> init host in pre_enable? If I remember correctly even though the host
> >> is initialized it has to reinitialize during the first transfer - This
> >> is what the Exynos requirement is. Please correct or explain here.
> >>
> >> This is a matter of enabling power regulator(s) in the right order and doing the host initialization in the right moment. It was never a matter of re-initialization. See the current code for the reference (it uses the same approach as my above change). I've already explained that here:
> >>
> >> https://lore.kernel.org/all/e96197f9-948a-997e-5453-9f9d179b5f5a@samsung.com/
> >>
> >> If you would like to see the exact proper moment of the dsi host initialization on the Exynos see the code here:
> >>
> >> https://protect2.fireeye.com/v1/url?k=5dc33900-0258001f-5dc2b24f-000babdfecba-f7c1a2a1905c83ca&q=1&e=f086bfdb-9055-48bd-b9c2-5dffb6c0d558&u=https%3A%2F%2Fgithub.com%2Fmszyprow%2Flinux%2Ftree%2Fv5.18-next-20220511-dsi-rework and patches adding mipi_dsi_host_init() to panel/bridge drivers.
> > As I said before, the downstream bridge needs an explicit call to host
> > init via mipi_dsi_host_init - this is indeed not a usual use-case
> > scenario. Let's handle this with a REINIT fix and see if we can update
> > this later to handle both scenarios.
> >
> > Would you please test this repo, I have included all.
> >
> > https://gitlab.com/openedev/kernel/-/commits/imx8mm-dsi-v10
>
> This doesn't work on TM2e board. Give me some time to find why...

May be some mode_flags changes in the panel driver.

Jagan.