[PATCH] [RFC] soc: imx: imx8m-blk-ctrl: Split clock prepare from clock enable in the domain
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Mon Oct 24 17:25:31 PDT 2022
Hi Marek,
Thank you for the patch.
On Mon, Oct 24, 2022 at 05:09:47PM +0200, Marek Vasut wrote:
> It is possible for clk_disable_unused() to trigger lockdep warning
> regarding lock ordering in this driver. This happens in case of the
> following conditions:
>
> A) clock core clk_disable_unused() triggers the following sequence in a
> driver which also uses blkctrl domain:
> - clk_prepare_lock() -> obtains clock core prepare_lock
> - pm_runtime_get*() -> obtains &blk_ctrl_genpd_lock_class
>
> B) driver powers up a power domain and triggers the following sequence
> in blkctrl:
> - pm_runtime_get_sync() -> obtains &blk_ctrl_genpd_lock_class
> - clk_bulk_prepare_enable() -> obtains clock core prepare_lock
>
> This can lead to a deadlock in case A and B runs on separate CPUs.
>
> To avoid the deadlock, split clk_*prepare() from clk_*enable() and
> call the former before pm_runtime_get_sync(). This way, the blkctrl
> driver always claims the prepare_lock before blk_ctrl_genpd_lock_class
> and the deadlock is avoided.
I'm afraid I'm still getting occasional warnings from lockdep :-( This
one happened at boot time:
[ 17.837243]
[ 17.837254] ======================================================
[ 17.837256] WARNING: possible circular locking dependency detected
[ 17.837260] 6.1.0-rc2-00199-gd504fb27855a-dirty #301 Not tainted
[ 17.837265] ------------------------------------------------------
[ 17.837267] kworker/u8:6/152 is trying to acquire lock:
[ 17.837273] ffff000000eab6f0 (&blk_ctrl_genpd_lock_class){+.+.}-{3:3}, at: genpd_lock_mtx+0x20/0x30
[ 17.837300]
[ 17.837300] but task is already holding lock:
[ 17.837302] ffff800009c1e5e8 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock+0x34/0xb0
[ 17.837321]
[ 17.837321] which lock already depends on the new lock.
[ 17.837321]
[ 17.837323]
[ 17.837323] the existing dependency chain (in reverse order) is:
[ 17.837326]
[ 17.837326] -> #1 (prepare_lock){+.+.}-{3:3}:
[ 17.837337] lock_acquire+0x68/0x90
[ 17.837345] __mutex_lock+0x8c/0x420
[ 17.837354] mutex_lock_nested+0x34/0x40
[ 17.837360] clk_prepare_lock+0x54/0xb0
[ 17.837367] clk_unprepare+0x2c/0x50
[ 17.837373] clk_bulk_unprepare+0x44/0x60
[ 17.837380] imx8mp_blk_ctrl_power_off+0xb4/0x100
[ 17.837386] _genpd_power_off+0x9c/0x180
[ 17.837392] genpd_power_off.part.0.isra.0+0x130/0x2a0
[ 17.837399] genpd_power_off_work_fn+0x6c/0x90
[ 17.837405] process_one_work+0x294/0x6b0
[ 17.837412] worker_thread+0x7c/0x450
[ 17.837416] kthread+0x114/0x120
[ 17.837424] ret_from_fork+0x10/0x20
[ 17.837431]
[ 17.837431] -> #0 (&blk_ctrl_genpd_lock_class){+.+.}-{3:3}:
[ 17.837442] __lock_acquire+0x1148/0x1910
[ 17.837448] lock_acquire.part.0+0xec/0x260
[ 17.837454] lock_acquire+0x68/0x90
[ 17.837459] __mutex_lock+0x8c/0x420
[ 17.837466] mutex_lock_nested+0x34/0x40
[ 17.837472] genpd_lock_mtx+0x20/0x30
[ 17.837478] genpd_runtime_resume+0xfc/0x2e0
[ 17.837484] __rpm_callback+0x50/0x1b0
[ 17.837492] rpm_callback+0x74/0x80
[ 17.837499] rpm_resume+0x434/0x6e0
[ 17.837505] __pm_runtime_resume+0x54/0xa0
[ 17.837512] clk_pm_runtime_get.part.0.isra.0+0x24/0xa0
[ 17.837518] clk_core_set_rate_nolock+0xbc/0x2b0
[ 17.837524] clk_set_rate+0x40/0xa0
[ 17.837529] lcdif_crtc_atomic_enable+0x98/0x880 [imx_lcdif]
[ 17.837544] drm_atomic_helper_commit_modeset_enables+0xac/0x2b0
[ 17.837551] drm_atomic_helper_commit_tail_rpm+0x58/0xb0
[ 17.837558] commit_tail+0xac/0x1a0
[ 17.837563] drm_atomic_helper_commit+0x1a0/0x1c0
[ 17.837569] drm_atomic_commit+0x94/0x130
[ 17.837574] drm_client_modeset_commit_atomic+0x230/0x2a0
[ 17.837582] drm_client_modeset_commit_locked+0x68/0x1d0
[ 17.837588] drm_client_modeset_commit+0x38/0x60
[ 17.837594] drm_fb_helper_set_par+0xd4/0x130
[ 17.837600] fbcon_init+0x3d4/0x540
[ 17.837606] visual_init+0xb8/0x110
[ 17.837613] do_bind_con_driver.isra.0+0x1c8/0x3a0
[ 17.837620] do_take_over_console+0x148/0x200
[ 17.837627] do_fbcon_takeover+0x74/0xf0
[ 17.837632] fbcon_fb_registered+0x18c/0x200
[ 17.837637] register_framebuffer+0x1bc/0x2b0
[ 17.837645] __drm_fb_helper_initial_config_and_unlock+0x338/0x5c0
[ 17.837650] drm_fbdev_client_hotplug+0xd8/0x1c0
[ 17.837656] drm_fbdev_generic_setup+0xbc/0x1b0
[ 17.837661] lcdif_probe+0x2b0/0x310 [imx_lcdif]
[ 17.837672] platform_probe+0x70/0xf0
[ 17.837678] really_probe+0xc8/0x3e0
[ 17.837685] __driver_probe_device+0x84/0x190
[ 17.837692] driver_probe_device+0x44/0x120
[ 17.837699] __device_attach_driver+0xc4/0x160
[ 17.837707] bus_for_each_drv+0x80/0xe0
[ 17.837713] __device_attach+0xb0/0x1f0
[ 17.837720] device_initial_probe+0x1c/0x30
[ 17.837727] bus_probe_device+0xa4/0xb0
[ 17.837734] deferred_probe_work_func+0xac/0x100
[ 17.837740] process_one_work+0x294/0x6b0
[ 17.837746] worker_thread+0x7c/0x450
[ 17.837751] kthread+0x114/0x120
[ 17.837758] ret_from_fork+0x10/0x20
[ 17.837764]
[ 17.837764] other info that might help us debug this:
[ 17.837764]
[ 17.837766] Possible unsafe locking scenario:
[ 17.837766]
[ 17.837768] CPU0 CPU1
[ 17.837770] ---- ----
[ 17.837772] lock(prepare_lock);
[ 17.837779] lock(&blk_ctrl_genpd_lock_class);
[ 17.837785] lock(prepare_lock);
[ 17.837790] lock(&blk_ctrl_genpd_lock_class);
[ 17.837796]
[ 17.837796] *** DEADLOCK ***
[ 17.837796]
[ 17.837799] 11 locks held by kworker/u8:6/152:
[ 17.837803] #0: ffff000000040938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1fc/0x6b0
[ 17.837821] #1: ffff80000b74bdd0 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x1fc/0x6b0
[ 17.837838] #2: ffff0000003f58f8 (&dev->mutex){....}-{3:3}, at: __device_attach+0x40/0x1f0
[ 17.837856] #3: ffff800009c1ddc0 (registration_lock){+.+.}-{3:3}, at: register_framebuffer+0x4c/0x2b0
[ 17.837875] #4: ffff800009ae4e68 (console_lock){+.+.}-{0:0}, at: fbcon_fb_registered+0x1f8/0x200
[ 17.837892] #5: ffff000002f1ee78 (&helper->lock){+.+.}-{3:3}, at: drm_fb_helper_set_par+0x98/0x130
[ 17.837909] #6: ffff0000038611a8 (&dev->master_mutex){+.+.}-{3:3}, at: drm_master_internal_acquire+0x2c/0x70
[ 17.837928] #7: ffff000002f1ec98 (&client->modeset_mutex){+.+.}-{3:3}, at: drm_client_modeset_commit_locked+0x34/0x1d0
[ 17.837947] #8: ffff80000b74b690 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_client_modeset_commit_atomic+0x50/0x2a0
[ 17.837964] #9: ffff000003863138 (crtc_ww_class_mutex){+.+.}-{3:3}, at: drm_modeset_lock+0x48/0x130
[ 17.837984] #10: ffff800009c1e5e8 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock+0x34/0xb0
[ 17.838003]
[ 17.838003] stack backtrace:
[ 17.838007] CPU: 1 PID: 152 Comm: kworker/u8:6 Not tainted 6.1.0-rc2-00199-gd504fb27855a-dirty #301
[ 17.838013] Hardware name: Polyhex Debix Model A i.MX8MPlus board (DT)
[ 17.838018] Workqueue: events_unbound deferred_probe_work_func
[ 17.838029] Call trace:
[ 17.838031] dump_backtrace+0xe4/0x140
[ 17.838042] show_stack+0x20/0x50
[ 17.838049] dump_stack_lvl+0x9c/0xd8
[ 17.838055] dump_stack+0x18/0x34
[ 17.838060] print_circular_bug+0x1f8/0x200
[ 17.838066] check_noncircular+0x160/0x180
[ 17.838072] __lock_acquire+0x1148/0x1910
[ 17.838078] lock_acquire.part.0+0xec/0x260
[ 17.838084] lock_acquire+0x68/0x90
[ 17.838089] __mutex_lock+0x8c/0x420
[ 17.838098] mutex_lock_nested+0x34/0x40
[ 17.838104] genpd_lock_mtx+0x20/0x30
[ 17.838110] genpd_runtime_resume+0xfc/0x2e0
[ 17.838117] __rpm_callback+0x50/0x1b0
[ 17.838125] rpm_callback+0x74/0x80
[ 17.838132] rpm_resume+0x434/0x6e0
[ 17.838138] __pm_runtime_resume+0x54/0xa0
[ 17.838145] clk_pm_runtime_get.part.0.isra.0+0x24/0xa0
[ 17.838150] clk_core_set_rate_nolock+0xbc/0x2b0
[ 17.838157] clk_set_rate+0x40/0xa0
[ 17.838162] lcdif_crtc_atomic_enable+0x98/0x880 [imx_lcdif]
[ 17.838175] drm_atomic_helper_commit_modeset_enables+0xac/0x2b0
[ 17.838182] drm_atomic_helper_commit_tail_rpm+0x58/0xb0
[ 17.838188] commit_tail+0xac/0x1a0
[ 17.838194] drm_atomic_helper_commit+0x1a0/0x1c0
[ 17.838200] drm_atomic_commit+0x94/0x130
[ 17.838205] drm_client_modeset_commit_atomic+0x230/0x2a0
[ 17.838212] drm_client_modeset_commit_locked+0x68/0x1d0
[ 17.838218] drm_client_modeset_commit+0x38/0x60
[ 17.838224] drm_fb_helper_set_par+0xd4/0x130
[ 17.838230] fbcon_init+0x3d4/0x540
[ 17.838235] visual_init+0xb8/0x110
[ 17.838243] do_bind_con_driver.isra.0+0x1c8/0x3a0
[ 17.838250] do_take_over_console+0x148/0x200
[ 17.838257] do_fbcon_takeover+0x74/0xf0
[ 17.838262] fbcon_fb_registered+0x18c/0x200
[ 17.838268] register_framebuffer+0x1bc/0x2b0
[ 17.838275] __drm_fb_helper_initial_config_and_unlock+0x338/0x5c0
[ 17.838282] drm_fbdev_client_hotplug+0xd8/0x1c0
[ 17.838288] drm_fbdev_generic_setup+0xbc/0x1b0
[ 17.838293] lcdif_probe+0x2b0/0x310 [imx_lcdif]
[ 17.838304] platform_probe+0x70/0xf0
[ 17.838309] really_probe+0xc8/0x3e0
[ 17.838316] __driver_probe_device+0x84/0x190
[ 17.838323] driver_probe_device+0x44/0x120
[ 17.838330] __device_attach_driver+0xc4/0x160
[ 17.838338] bus_for_each_drv+0x80/0xe0
[ 17.838344] __device_attach+0xb0/0x1f0
[ 17.838351] device_initial_probe+0x1c/0x30
[ 17.838358] bus_probe_device+0xa4/0xb0
[ 17.838365] deferred_probe_work_func+0xac/0x100
[ 17.838372] process_one_work+0x294/0x6b0
[ 17.838378] worker_thread+0x7c/0x450
[ 17.838383] kthread+0x114/0x120
[ 17.838390] ret_from_fork+0x10/0x20
> Signed-off-by: Marek Vasut <marex at denx.de>
> ---
> Cc: Fabio Estevam <festevam at denx.de>
> Cc: Jacky Bai <ping.bai at nxp.com>
> Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> Cc: Lucas Stach <l.stach at pengutronix.de>
> Cc: Peng Fan <peng.fan at nxp.com>
> Cc: Shawn Guo <shawnguo at kernel.org>
> Cc: Shengjiu Wang <shengjiu.wang at nxp.com>
> Cc: Stephen Boyd <sboyd at kernel.org>
> Cc: linux-clk at vger.kernel.org
> Cc: linux-imx at nxp.com
> To: linux-arm-kernel at lists.infradead.org
> ---
> drivers/soc/imx/imx8mp-blk-ctrl.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/soc/imx/imx8mp-blk-ctrl.c b/drivers/soc/imx/imx8mp-blk-ctrl.c
> index b7d4161fcda9c..571c98b5b005b 100644
> --- a/drivers/soc/imx/imx8mp-blk-ctrl.c
> +++ b/drivers/soc/imx/imx8mp-blk-ctrl.c
> @@ -393,15 +393,21 @@ static int imx8mp_blk_ctrl_power_on(struct generic_pm_domain *genpd)
> struct imx8mp_blk_ctrl *bc = domain->bc;
> int ret;
>
> + ret = clk_bulk_prepare(data->num_clks, domain->clks);
> + if (ret) {
> + dev_err(bc->dev, "failed to enable clocks\n");
> + return ret;
> + }
> +
> /* make sure bus domain is awake */
> ret = pm_runtime_resume_and_get(bc->bus_power_dev);
> if (ret < 0) {
> dev_err(bc->dev, "failed to power up bus domain\n");
> - return ret;
> + goto rpm_put;
> }
>
> /* enable upstream clocks */
> - ret = clk_bulk_prepare_enable(data->num_clks, domain->clks);
> + ret = clk_bulk_enable(data->num_clks, domain->clks);
> if (ret) {
> dev_err(bc->dev, "failed to enable clocks\n");
> goto bus_put;
> @@ -426,9 +432,11 @@ static int imx8mp_blk_ctrl_power_on(struct generic_pm_domain *genpd)
> return 0;
>
> clk_disable:
> - clk_bulk_disable_unprepare(data->num_clks, domain->clks);
> + clk_bulk_disable(data->num_clks, domain->clks);
> bus_put:
> pm_runtime_put(bc->bus_power_dev);
> +rpm_put:
> + clk_bulk_unprepare(data->num_clks, domain->clks);
>
> return ret;
> }
--
Regards,
Laurent Pinchart
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