Re: [PATCH v2] drm/bridge: adv7533: remove dynamic lane switching from adv7533 bridge

[Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>]

On 12/03/2023 00:40, Adam Ford wrote:
> On Sat, Mar 11, 2023 at 4:02 PM Dmitry Baryshkov
> <dmitry.baryshkov@xxxxxxxxxx> wrote:
> > On 11/03/2023 23:53, Adam Ford wrote:
> > > On Sat, Mar 11, 2023 at 3:40 PM Dmitry Baryshkov
> > > <dmitry.baryshkov@xxxxxxxxxx> wrote:
> > > > "Hi Abhinav,
> > > >
> > > > On Sat, 11 Mar 2023 at 23:18, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:
> > > > > Hi Adam
> > > > >
> > > > > On 3/11/2023 9:28 AM, Adam Ford wrote:
> > > > > > On Thu, Oct 13, 2022 at 3:39 AM Robert Foss <robert.foss@xxxxxxxxxx> wrote:
> > > > > > > On Tue, 11 Oct 2022 at 23:11, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:
> > > > > > > > adv7533 bridge tries to dynamically switch lanes based on the
> > > > > > > > mode by detaching and attaching the mipi dsi device.
> > > > > > > >
> > > > > > > > This approach is incorrect because this method of dynamic switch of
> > > > > > > > detaching and attaching the mipi dsi device also results in removing
> > > > > > > > and adding the component which is not necessary.
> > > > > > > >
> > > > > > > > This approach is also prone to deadlocks. So for example, on the
> > > > > > > > db410c whenever this path is executed with lockdep enabled,
> > > > > > > > this results in a deadlock due to below ordering of locks.
> > > > > > > >
> > > > > > > > -> #1 (crtc_ww_class_acquire){+.+.}-{0:0}:
> > > > > > > >            lock_acquire+0x6c/0x90
> > > > > > > >            drm_modeset_acquire_init+0xf4/0x150
> > > > > > > >            drmm_mode_config_init+0x220/0x770
> > > > > > > >            msm_drm_bind+0x13c/0x654
> > > > > > > >            try_to_bring_up_aggregate_device+0x164/0x1d0
> > > > > > > >            __component_add+0xa8/0x174
> > > > > > > >            component_add+0x18/0x2c
> > > > > > > >            dsi_dev_attach+0x24/0x30
> > > > > > > >            dsi_host_attach+0x98/0x14c
> > > > > > > >            devm_mipi_dsi_attach+0x38/0xb0
> > > > > > > >            adv7533_attach_dsi+0x8c/0x110
> > > > > > > >            adv7511_probe+0x5a0/0x930
> > > > > > > >            i2c_device_probe+0x30c/0x350
> > > > > > > >            really_probe.part.0+0x9c/0x2b0
> > > > > > > >            __driver_probe_device+0x98/0x144
> > > > > > > >            driver_probe_device+0xac/0x14c
> > > > > > > >            __device_attach_driver+0xbc/0x124
> > > > > > > >            bus_for_each_drv+0x78/0xd0
> > > > > > > >            __device_attach+0xa8/0x1c0
> > > > > > > >            device_initial_probe+0x18/0x24
> > > > > > > >            bus_probe_device+0xa0/0xac
> > > > > > > >            deferred_probe_work_func+0x90/0xd0
> > > > > > > >            process_one_work+0x28c/0x6b0
> > > > > > > >            worker_thread+0x240/0x444
> > > > > > > >            kthread+0x110/0x114
> > > > > > > >            ret_from_fork+0x10/0x20
> > > > > > > >
> > > > > > > > -> #0 (component_mutex){+.+.}-{3:3}:
> > > > > > > >            __lock_acquire+0x1280/0x20ac
> > > > > > > >            lock_acquire.part.0+0xe0/0x230
> > > > > > > >            lock_acquire+0x6c/0x90
> > > > > > > >            __mutex_lock+0x84/0x400
> > > > > > > >            mutex_lock_nested+0x3c/0x70
> > > > > > > >            component_del+0x34/0x170
> > > > > > > >            dsi_dev_detach+0x24/0x30
> > > > > > > >            dsi_host_detach+0x20/0x64
> > > > > > > >            mipi_dsi_detach+0x2c/0x40
> > > > > > > >            adv7533_mode_set+0x64/0x90
> > > > > > > >            adv7511_bridge_mode_set+0x210/0x214
> > > > > > > >            drm_bridge_chain_mode_set+0x5c/0x84
> > > > > > > >            crtc_set_mode+0x18c/0x1dc
> > > > > > > >            drm_atomic_helper_commit_modeset_disables+0x40/0x50
> > > > > > > >            msm_atomic_commit_tail+0x1d0/0x6e0
> > > > > > > >            commit_tail+0xa4/0x180
> > > > > > > >            drm_atomic_helper_commit+0x178/0x3b0
> > > > > > > >            drm_atomic_commit+0xa4/0xe0
> > > > > > > >            drm_client_modeset_commit_atomic+0x228/0x284
> > > > > > > >            drm_client_modeset_commit_locked+0x64/0x1d0
> > > > > > > >            drm_client_modeset_commit+0x34/0x60
> > > > > > > >            drm_fb_helper_lastclose+0x74/0xcc
> > > > > > > >            drm_lastclose+0x3c/0x80
> > > > > > > >            drm_release+0xfc/0x114
> > > > > > > >            __fput+0x70/0x224
> > > > > > > >            ____fput+0x14/0x20
> > > > > > > >            task_work_run+0x88/0x1a0
> > > > > > > >            do_exit+0x350/0xa50
> > > > > > > >            do_group_exit+0x38/0xa4
> > > > > > > >            __wake_up_parent+0x0/0x34
> > > > > > > >            invoke_syscall+0x48/0x114
> > > > > > > >            el0_svc_common.constprop.0+0x60/0x11c
> > > > > > > >            do_el0_svc+0x30/0xc0
> > > > > > > >            el0_svc+0x58/0x100
> > > > > > > >            el0t_64_sync_handler+0x1b0/0x1bc
> > > > > > > >            el0t_64_sync+0x18c/0x190
> > > > > > > >
> > > > > > > > Due to above reasons, remove the dynamic lane switching
> > > > > > > > code from adv7533 bridge chip and filter out the modes
> > > > > > > > which would need different number of lanes as compared
> > > > > > > > to the initialization time using the mode_valid callback.
> > > > > > > >
> > > > > > > > This can be potentially re-introduced by using the pre_enable()
> > > > > > > > callback but this needs to be evaluated first whether such an
> > > > > > > > approach will work so this will be done with a separate change.
> > > > > > > >
> > > > > > > > changes since RFC:
> > > > > > > >            - Fix commit text and add TODO comment
> > > > > > > >
> > > > > > > > changes in v2:
> > > > > > > >            - Fix checkpatch formatting errors
> > > > > > > >
> > > > > > > > Fixes: 62b2f026cd8e ("drm/bridge: adv7533: Change number of DSI lanes dynamically")
> > > > > > > > Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/16
> > > > > > > > Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > > > > > > > Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> > > > > > > > Reviewed-by: Robert Foss <robert.foss@xxxxxxxxxx>
> > > > > > > > Link: https://lore.kernel.org/r/1661797363-7564-1-git-send-email-quic_abhinavk@xxxxxxxxxxx
> > > > > > > > ---
> > > > > > > >     drivers/gpu/drm/bridge/adv7511/adv7511.h     |  3 ++-
> > > > > > > >     drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 18 ++++++++++++++----
> > > > > > > >     drivers/gpu/drm/bridge/adv7511/adv7533.c     | 25 +++++++++++++------------
> > > > > > > >     3 files changed, 29 insertions(+), 17 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511.h b/drivers/gpu/drm/bridge/adv7511/adv7511.h
> > > > > > > > index a031a0cd1f18..1053d185b24c 100644
> > > > > > > > --- a/drivers/gpu/drm/bridge/adv7511/adv7511.h
> > > > > > > > +++ b/drivers/gpu/drm/bridge/adv7511/adv7511.h
> > > > > > > > @@ -405,7 +405,8 @@ static inline int adv7511_cec_init(struct device *dev, struct adv7511 *adv7511)
> > > > > > > >
> > > > > > > >     void adv7533_dsi_power_on(struct adv7511 *adv);
> > > > > > > >     void adv7533_dsi_power_off(struct adv7511 *adv);
> > > > > > > > -void adv7533_mode_set(struct adv7511 *adv, const struct drm_display_mode *mode);
> > > > > > > > +enum drm_mode_status adv7533_mode_valid(struct adv7511 *adv,
> > > > > > > > +                                       const struct drm_display_mode *mode);
> > > > > > > >     int adv7533_patch_registers(struct adv7511 *adv);
> > > > > > > >     int adv7533_patch_cec_registers(struct adv7511 *adv);
> > > > > > > >     int adv7533_attach_dsi(struct adv7511 *adv);
> > > > > > > > diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > > > > > index 38bf28720f3a..4bc7aac94a16 100644
> > > > > > > > --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > > > > > +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > > > > > @@ -697,7 +697,7 @@ adv7511_detect(struct adv7511 *adv7511, struct drm_connector *connector)
> > > > > > > >     }
> > > > > > > >
> > > > > > > >     static enum drm_mode_status adv7511_mode_valid(struct adv7511 *adv7511,
> > > > > > > > -                             struct drm_display_mode *mode)
> > > > > > > > +                             const struct drm_display_mode *mode)
> > > > > > > >     {
> > > > > > > >            if (mode->clock > 165000)
> > > > > > > >                    return MODE_CLOCK_HIGH;
> > > > > > > > @@ -791,9 +791,6 @@ static void adv7511_mode_set(struct adv7511 *adv7511,
> > > > > > > >            regmap_update_bits(adv7511->regmap, 0x17,
> > > > > > > >                    0x60, (vsync_polarity << 6) | (hsync_polarity << 5));
> > > > > > > >
> > > > > > > > -       if (adv7511->type == ADV7533 || adv7511->type == ADV7535)
> > > > > > > > -               adv7533_mode_set(adv7511, adj_mode);
> > > > > > > > -
> > > > > > > >            drm_mode_copy(&adv7511->curr_mode, adj_mode);
> > > > > > > >
> > > > > > > >            /*
> > > > > > > > @@ -913,6 +910,18 @@ static void adv7511_bridge_mode_set(struct drm_bridge *bridge,
> > > > > > > >            adv7511_mode_set(adv, mode, adj_mode);
> > > > > > > >     }
> > > > > > > >
> > > > > > > > +static enum drm_mode_status adv7511_bridge_mode_valid(struct drm_bridge *bridge,
> > > > > > > > +                                                     const struct drm_display_info *info,
> > > > > > > > +               const struct drm_display_mode *mode)
> > > > > > > > +{
> > > > > > > > +       struct adv7511 *adv = bridge_to_adv7511(bridge);
> > > > > > > > +
> > > > > > > > +       if (adv->type == ADV7533 || adv->type == ADV7535)
> > > > > > > > +               return adv7533_mode_valid(adv, mode);
> > > > > > > > +       else
> > > > > > > > +               return adv7511_mode_valid(adv, mode);
> > > > > > > > +}
> > > > > > > > +
> > > > > > > >     static int adv7511_bridge_attach(struct drm_bridge *bridge,
> > > > > > > >                                     enum drm_bridge_attach_flags flags)
> > > > > > > >     {
> > > > > > > > @@ -960,6 +969,7 @@ static const struct drm_bridge_funcs adv7511_bridge_funcs = {
> > > > > > > >            .enable = adv7511_bridge_enable,
> > > > > > > >            .disable = adv7511_bridge_disable,
> > > > > > > >            .mode_set = adv7511_bridge_mode_set,
> > > > > > > > +       .mode_valid = adv7511_bridge_mode_valid,
> > > > > > > >            .attach = adv7511_bridge_attach,
> > > > > > > >            .detect = adv7511_bridge_detect,
> > > > > > > >            .get_edid = adv7511_bridge_get_edid,
> > > > > > > > diff --git a/drivers/gpu/drm/bridge/adv7511/adv7533.c b/drivers/gpu/drm/bridge/adv7511/adv7533.c
> > > > > > > > index ef6270806d1d..258c79d4dab0 100644
> > > > > > > > --- a/drivers/gpu/drm/bridge/adv7511/adv7533.c
> > > > > > > > +++ b/drivers/gpu/drm/bridge/adv7511/adv7533.c
> > > > > > > > @@ -100,26 +100,27 @@ void adv7533_dsi_power_off(struct adv7511 *adv)
> > > > > > > >            regmap_write(adv->regmap_cec, 0x27, 0x0b);
> > > > > > > >     }
> > > > > > > >
> > > > > > > > -void adv7533_mode_set(struct adv7511 *adv, const struct drm_display_mode *mode)
> > > > > > > > +enum drm_mode_status adv7533_mode_valid(struct adv7511 *adv,
> > > > > > > > +                                       const struct drm_display_mode *mode)
> > > > > > > >     {
> > > > > > > > +       int lanes;
> > > > > > > >            struct mipi_dsi_device *dsi = adv->dsi;
> > > > > > > > -       int lanes, ret;
> > > > > > > > -
> > > > > > > > -       if (adv->num_dsi_lanes != 4)
> > > > > > > > -               return;
> > > > > > > >
> > > > > > > >            if (mode->clock > 80000)
> > > > > > > >                    lanes = 4;
> > > > > > > >            else
> > > > > > > >                    lanes = 3;
> > > > > >
> > > > > > I know this thread is a bit old, but I have an i.MX8M Mini with an
> > > > > > adv7535 HDMI bridge, and I'm able to display video on a 4-lane
> > > > > > interface with a clock as low as 27000.
> > > > >
> > > > > Looks like this condition is not tracking how low the bridge can support
> > > > > with 4 lanes but how high you can support with 3 lanes. Thats the issue.
> > > > >
> > > > > This condition has been this way since the original bridge driver:
> > > > >
> > > > > drm/bridge: adv7533: Change number of DSI lanes dynamically
> > > > >
> > > > > Yes, its possible that with 4 lanes you can support a lower rate but
> > > > > with 3 lanes you cannot support a higher one. So that needs to be handled.
> > > > >
> > > > > The extra conditional's intention was to make sure that if you try to
> > > > > switch to a mode which has a different number of lanes than what was set
> > > > > in the device tree (basically dynamic mode switch) then fail that.
> > > > >
> > > > > So perhaps this condition can be modified to :
> > > > >
> > > > > if (num_dsi_lanes < 4 && mode->clock > 80000)
> > > > >           return MODE_BAD;
> > > > >
> > > > > I think that should fix your issue. You can set the number of lanes to 4
> > > > > for your board if it supports that using the DT node adi,dsi-lanes.
> > >
> > > Thanks to both of you for the ideas.
> > >
> > > > I went on and looked into the adv7533 datasheet. Strangely enough
> > > > these conditions do not correspond to the limitations from the
> > > > datasheet:
> > > > - "pixel clocks of up to 80 MHz",
> > > > - "each [DSI lane] running up to 800 Mbps"
> > > >
> > > > So probably the conditions should be as following:
> > > >
> > > > if (mode->clock > 80000)
> > > >      return MODE_CLOCK_HIGH;
> > >
> > > This is consistent with what is happening on the 7511.
> > >
> > > > if (mode->clock * bpp > 800000 * adv->num_dsi_lanes)
> > > >       return MODE_CLOCK_HIGH;
> > > >
> > > > See https://www.analog.com/media/en/technical-documentation/data-sheets/adv7533.pdf
> > >
> > > These numbers would need to be changed for the 7535, the device I am
> > > using.  So I'll submit a patch which checks these with different max
> > > values depending on whether or not the device is 7533 or 7535.
> >
> > For adv7535 the max pixel clock seems to 148.5 MHz, max lane clock is
> > 891 MHz.
> >
> > I'm slightly confused about adv7511, whose datasheet contains just a
> > single number of '225 MHz'.
>
> This is what I did:
>
> u8 bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
> ...
>
> /* Check max clock for either 7533 or 7535 */
> if (mode->clock > (adv->type == ADV7533 ? 80000 : 148500))
>       return MODE_CLOCK_HIGH;
>
> /* Check max clock for each lane */
> max_lane_freq = (adv->type == ADV7533 ? 800000 : 891000);
>
> if (mode->clock * bpp > max_lane_freq * adv->num_dsi_lanes)
>       return MODE_CLOCK_HIGH;
>
> Does that look OK to everyone?
>
> If so, I'll push a formal patch with a fixes tag

LGTM. You might want to split this to two separate functions (7533 vs 
7535), but it's up to your taste.

.
> adam
> > > adam
> > >
> > > > > > > > -       if (lanes != dsi->lanes) {
> > > > > > > > -               mipi_dsi_detach(dsi);
> > > > > > > > -               dsi->lanes = lanes;
> > > > > > > > -               ret = mipi_dsi_attach(dsi);
> > > > > > > > -               if (ret)
> > > > > > > > -                       dev_err(&dsi->dev, "failed to change host lanes\n");
> > > > > > > > -       }
> > > > > > > > +       /*
> > > > > > > > +        * TODO: add support for dynamic switching of lanes
> > > > > > > > +        * by using the bridge pre_enable() op . Till then filter
> > > > > > > > +        * out the modes which shall need different number of lanes
> > > > > > > > +        * than what was configured in the device tree.
> > > > > > > > +        */
> > > > > > > > +       if (lanes != dsi->lanes)
> > > > > > > > +               return MODE_BAD;
> > > > > > > > +
> > > > > >
> > > > > > My board doesn't currently support dynamic switching, but I'd like to
> > > > > > keep 4-lanes all the time.  However, this return eliminates several
> > > > > > resolutions that I can successfully display.
> > > > > > I'd like to eliminate this error, so it works on the imx8m
> > > > > > mini/nano/plus, but I am not sure the best approach without breaking
> > > > > > someone else's board.
> > > > > >    > I was thinking I could add a flag to disable dynamic switching.  If
> > > > > > that flag is set, we'd return MODE_OK here.
> > > > > >
> > > > > > Does anyone have any suggestions on an apporach?
> > > > > >
> > > > > > adam
> > > > >
> > > > > I am thinking of this solution
> > > > >
> > > > > if (num_dsi_lanes < 4 && mode->clock > 80000)
> > > > >           return MODE_BAD;
> > > > >
> > > > > So lets say some user tried to set number of lanes to 3 but tries a mode
> > > > > needing > 80000 clock then fail.
> > > > >
> > > > > That way we still dont support dynamic mode switch but also dont limit
> > > > > the modes which can be supported with 4 lanes.
> > > > >
> > > > > > > > +       return MODE_OK;
> > > > > > > >     }
> > > > > > > >
> > > > > > > >     int adv7533_patch_registers(struct adv7511 *adv)
> > > > > > > > --
> > > > > > > > 2.7.4
> > > > > > >
> > > > > > > Applied to drm-misc-next.
> > > >
> > > >
> > > >
> > > > --
> > > > With best wishes
> > > > Dmitry
> >
> > --
> > With best wishes
> > Dmitry

--
With best wishes
Dmitry