[PATCH v2] drm/bridge: adv7533: remove dynamic lane switching from adv7533 bridge
Dmitry Baryshkov
dmitry.baryshkov at linaro.org
Sat Mar 11 21:40:18 UTC 2023
"Hi Abhinav,
On Sat, 11 Mar 2023 at 23:18, Abhinav Kumar <quic_abhinavk at quicinc.com> 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 at linaro.org> wrote:
> >>
> >> On Tue, 11 Oct 2022 at 23:11, Abhinav Kumar <quic_abhinavk at quicinc.com> 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 at linaro.org>
> >>> Signed-off-by: Abhinav Kumar <quic_abhinavk at quicinc.com>
> >>> Reviewed-by: Robert Foss <robert.foss at linaro.org>
> >>> Link: https://lore.kernel.org/r/1661797363-7564-1-git-send-email-quic_abhinavk@quicinc.com
> >>> ---
> >>> 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.
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;
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
>
> >>>
> >>> - 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
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