[RFC] drm/bridge: adv7533: remove dynamic lane switching from adv7533 bridge
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Tue Aug 9 19:40:58 UTC 2022
Hi Abhinav,
Thank you for the patch.
On Mon, Aug 08, 2022 at 05:35:30PM -0700, Abhinav Kumar 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 as per the DSI spec the
> number of lanes is fixed at the time of system design or initial
> configuration and may not change dynamically.
Is that really so ? The number of lanes connected on the board is
certainlyset at design time, but a lower number of lanes can be used at
runtime. It shouldn't change dynamically while the display is on, but it
could change at mode set time.
> In addition 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.
Yes, that doesn't look good, and the .mode_valid() operation is
definitely not the right point where to set the number of lanes.
> 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.
>
> Suggested-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> Signed-off-by: Abhinav Kumar <quic_abhinavk at 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 9e3bb8a8ee40..0a7cec80b75d 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511.h
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511.h
> @@ -417,7 +417,8 @@ 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 5bb9300040dd..1115ef9be83c 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..4a6d45edf431 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;
>
> - 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");
> - }
> + /*
> + * number of lanes cannot be changed after initialization
> + * as per section 6.1 of the DSI specification. Hence 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;
> +
> + return MODE_OK;
> }
>
> int adv7533_patch_registers(struct adv7511 *adv)
--
Regards,
Laurent Pinchart
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