[PATCH] [RFC] soc: imx: gpcv2: Split clock prepare from clock enable in the domain
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Sun Oct 23 16:25:00 PDT 2022
Hi Marek,
Thank you for the patch.
On Sun, Oct 23, 2022 at 06:40:00PM +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 GPCv2 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 GPCv2:
> - 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 GPCv2
> driver always claims the prepare_lock before blk_ctrl_genpd_lock_class
> and the deadlock is avoided.
>
> The imx8m and imx8mp block controller drivers likely need similar fix.
Indeed, I'm getting a warning from lockdep:
[ 3019.012615] ======================================================
[ 3019.018796] WARNING: possible circular locking dependency detected
[ 3019.024978] 6.1.0-rc1-00233-gd15fae6050bd #298 Not tainted
[ 3019.030466] ------------------------------------------------------
[ 3019.036644] cam/377 is trying to acquire lock:
[ 3019.041092] ffff800009c1e5e8 (prepare_lock){+.+.}-{3:3}, at: clk_prepare_lock+0x54/0xb0
[ 3019.049131]
[ 3019.049131] but task is already holding lock:
[ 3019.054962] ffff000000f50f90 (&blk_ctrl_genpd_lock_class){+.+.}-{3:3}, at: genpd_lock_mtx+0x20/0x30
[ 3019.064036]
[ 3019.064036] which lock already depends on the new lock.
[ 3019.064036]
[ 3019.072212]
[ 3019.072212] the existing dependency chain (in reverse order) is:
[ 3019.079697]
[ 3019.079697] -> #1 (&blk_ctrl_genpd_lock_class){+.+.}-{3:3}:
[ 3019.086759] lock_acquire+0x68/0x90
[ 3019.090774] __mutex_lock+0x8c/0x420
[ 3019.094878] mutex_lock_nested+0x34/0x40
[ 3019.099330] genpd_lock_mtx+0x20/0x30
[ 3019.103520] genpd_runtime_resume+0xfc/0x2e0
[ 3019.108316] __rpm_callback+0x50/0x1b0
[ 3019.112593] rpm_callback+0x74/0x80
[ 3019.116611] rpm_resume+0x434/0x6e0
[ 3019.120627] __pm_runtime_resume+0x54/0xa0
[ 3019.125250] clk_pm_runtime_get.part.0.isra.0+0x24/0xa0
[ 3019.131001] clk_core_set_rate_nolock+0xbc/0x2b0
[ 3019.136149] clk_set_rate+0x40/0xa0
[ 3019.140165] lcdif_crtc_atomic_enable+0x98/0x880 [imx_lcdif]
[ 3019.146364] drm_atomic_helper_commit_modeset_enables+0xac/0x2b0
[ 3019.152901] drm_atomic_helper_commit_tail_rpm+0x58/0xb0
[ 3019.158743] commit_tail+0xac/0x1a0
[ 3019.162757] drm_atomic_helper_commit+0x1a0/0x1c0
[ 3019.167986] drm_atomic_commit+0x94/0x130
[ 3019.172521] drm_client_modeset_commit_atomic+0x230/0x2a0
[ 3019.178449] drm_client_modeset_commit_locked+0x68/0x1d0
[ 3019.184290] drm_client_modeset_commit+0x38/0x60
[ 3019.189436] drm_fb_helper_set_par+0xd4/0x130
[ 3019.194319] fbcon_init+0x3d4/0x540
[ 3019.198334] visual_init+0xb8/0x110
[ 3019.202349] do_bind_con_driver.isra.0+0x1c8/0x3a0
[ 3019.207670] do_take_over_console+0x148/0x200
[ 3019.212557] do_fbcon_takeover+0x74/0xf0
[ 3019.217007] fbcon_fb_registered+0x18c/0x200
[ 3019.221803] register_framebuffer+0x1bc/0x2b0
[ 3019.226690] __drm_fb_helper_initial_config_and_unlock+0x338/0x5c0
[ 3019.233397] drm_fbdev_client_hotplug+0xd8/0x1c0
[ 3019.238541] drm_fbdev_generic_setup+0xbc/0x1b0
[ 3019.243599] lcdif_probe+0x2b0/0x310 [imx_lcdif]
[ 3019.248751] platform_probe+0x70/0xf0
[ 3019.252940] really_probe+0xc8/0x3e0
[ 3019.257046] __driver_probe_device+0x84/0x190
[ 3019.261933] driver_probe_device+0x44/0x120
[ 3019.266646] __device_attach_driver+0xc4/0x160
[ 3019.271618] bus_for_each_drv+0x80/0xe0
[ 3019.275985] __device_attach+0xb0/0x1f0
[ 3019.280348] device_initial_probe+0x1c/0x30
[ 3019.285060] bus_probe_device+0xa4/0xb0
[ 3019.289426] deferred_probe_work_func+0xac/0x100
[ 3019.294575] process_one_work+0x294/0x6b0
[ 3019.299109] worker_thread+0x7c/0x450
[ 3019.303296] kthread+0x114/0x120
[ 3019.307052] ret_from_fork+0x10/0x20
[ 3019.311157]
[ 3019.311157] -> #0 (prepare_lock){+.+.}-{3:3}:
[ 3019.317005] __lock_acquire+0x1148/0x1910
[ 3019.321544] lock_acquire.part.0+0xec/0x260
[ 3019.326255] lock_acquire+0x68/0x90
[ 3019.326815] cpu cpu0: _set_opp_voltage: failed to set voltage (950000 950000 950000 mV): -110
[ 3019.330269] __mutex_lock+0x8c/0x420
[ 3019.338821] cpu cpu0: Failed to set regulator voltages: -110
[ 3019.342883] mutex_lock_nested+0x34/0x40
[ 3019.342894] clk_prepare_lock+0x54/0xb0
[ 3019.342904] clk_prepare+0x28/0x50
[ 3019.342913] clk_bulk_prepare+0x40/0xb0
[ 3019.342922] imx8mp_blk_ctrl_power_on+0x54/0x220
[ 3019.348599] cpufreq: __target_index: Failed to change cpu frequency: -110
[ 3019.353018] _genpd_power_on+0x9c/0x180
[ 3019.353026] genpd_power_on.part.0+0xac/0x1c0
[ 3019.386800] genpd_runtime_resume+0x110/0x2e0
[ 3019.391685] __rpm_callback+0x50/0x1b0
[ 3019.395964] rpm_callback+0x74/0x80
[ 3019.399982] rpm_resume+0x434/0x6e0
[ 3019.403999] __pm_runtime_resume+0x54/0xa0
[ 3019.408626] lcdif_crtc_atomic_enable+0xa4/0x880 [imx_lcdif]
[ 3019.414820] drm_atomic_helper_commit_modeset_enables+0xac/0x2b0
[ 3019.421355] drm_atomic_helper_commit_tail_rpm+0x58/0xb0
[ 3019.427195] commit_tail+0xac/0x1a0
[ 3019.431210] drm_atomic_helper_commit+0x1a0/0x1c0
[ 3019.436440] drm_atomic_commit+0x94/0x130
[ 3019.440978] drm_client_modeset_commit_atomic+0x230/0x2a0
[ 3019.446903] drm_client_modeset_commit_locked+0x68/0x1d0
[ 3019.452746] drm_client_modeset_commit+0x38/0x60
[ 3019.457891] drm_fbdev_client_restore+0x80/0xe0
[ 3019.462950] drm_client_dev_restore+0xa0/0x110
[ 3019.467920] drm_lastclose+0x40/0xb0
[ 3019.472023] drm_release+0x16c/0x190
[ 3019.476127] __fput+0x78/0x260
[ 3019.479711] ____fput+0x18/0x30
[ 3019.483378] task_work_run+0x88/0xe0
[ 3019.487484] do_notify_resume+0x20c/0x1430
[ 3019.492108] el0_svc+0x120/0x130
[ 3019.495862] el0t_64_sync_handler+0xbc/0x140
[ 3019.500658] el0t_64_sync+0x18c/0x190
[ 3019.504847]
[ 3019.504847] other info that might help us debug this:
[ 3019.504847]
[ 3019.512851] Possible unsafe locking scenario:
[ 3019.512851]
[ 3019.518768] CPU0 CPU1
[ 3019.523299] ---- ----
[ 3019.527832] lock(&blk_ctrl_genpd_lock_class);
[ 3019.532371] lock(prepare_lock);
[ 3019.538212] lock(&blk_ctrl_genpd_lock_class);
[ 3019.545269] lock(prepare_lock);
[ 3019.548590]
[ 3019.548590] *** DEADLOCK ***
[ 3019.548590]
[ 3019.554512] 7 locks held by cam/377:
[ 3019.558088] #0: ffff000002f0a2f0 (&dev->clientlist_mutex){+.+.}-{3:3}, at: drm_client_dev_restore+0x5c/0x110
[ 3019.568034] #1: ffff000002388a78 (&helper->lock){+.+.}-{3:3}, at: drm_fbdev_client_restore+0x78/0xe0
[ 3019.577283] #2: ffff000002f0a1a8 (&dev->master_mutex){+.+.}-{3:3}, at: drm_master_internal_acquire+0x2c/0x70
[ 3019.587227] #3: ffff000002388898 (&client->modeset_mutex){+.+.}-{3:3}, at: drm_client_modeset_commit_locked+0x34/0x1d0
[ 3019.598036] #4: ffff80000aa13b00 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_client_modeset_commit_atomic+0x50/0x2a0
[ 3019.608759] #5: ffff000003b78138 (crtc_ww_class_mutex){+.+.}-{3:3}, at: drm_modeset_lock+0x48/0x130
[ 3019.617924] #6: ffff000000f50f90 (&blk_ctrl_genpd_lock_class){+.+.}-{3:3}, at: genpd_lock_mtx+0x20/0x30
[ 3019.627427]
[ 3019.627427] stack backtrace:
[ 3019.631788] CPU: 0 PID: 377 Comm: cam Not tainted 6.1.0-rc1-00233-gd15fae6050bd #298
[ 3019.639538] Hardware name: Polyhex Debix Model A i.MX8MPlus board (DT)
[ 3019.646068] Call trace:
[ 3019.648516] dump_backtrace+0xe4/0x140
[ 3019.652274] show_stack+0x20/0x50
[ 3019.655596] dump_stack_lvl+0x9c/0xd8
[ 3019.659263] dump_stack+0x18/0x34
[ 3019.662582] print_circular_bug+0x1f8/0x200
[ 3019.666771] check_noncircular+0x160/0x180
[ 3019.670876] __lock_acquire+0x1148/0x1910
[ 3019.674891] lock_acquire.part.0+0xec/0x260
[ 3019.679084] lock_acquire+0x68/0x90
[ 3019.682582] __mutex_lock+0x8c/0x420
[ 3019.686164] mutex_lock_nested+0x34/0x40
[ 3019.690096] clk_prepare_lock+0x54/0xb0
[ 3019.693937] clk_prepare+0x28/0x50
[ 3019.697345] clk_bulk_prepare+0x40/0xb0
[ 3019.701192] imx8mp_blk_ctrl_power_on+0x54/0x220
[ 3019.705813] _genpd_power_on+0x9c/0x180
[ 3019.709655] genpd_power_on.part.0+0xac/0x1c0
[ 3019.714020] genpd_runtime_resume+0x110/0x2e0
[ 3019.718383] __rpm_callback+0x50/0x1b0
[ 3019.722140] rpm_callback+0x74/0x80
[ 3019.725638] rpm_resume+0x434/0x6e0
[ 3019.729133] __pm_runtime_resume+0x54/0xa0
[ 3019.733238] lcdif_crtc_atomic_enable+0xa4/0x880 [imx_lcdif]
[ 3019.738914] drm_atomic_helper_commit_modeset_enables+0xac/0x2b0
[ 3019.744927] drm_atomic_helper_commit_tail_rpm+0x58/0xb0
[ 3019.750248] commit_tail+0xac/0x1a0
[ 3019.753744] drm_atomic_helper_commit+0x1a0/0x1c0
[ 3019.758454] drm_atomic_commit+0x94/0x130
[ 3019.758815] cpu cpu0: _set_opp_voltage: failed to set voltage (950000 950000 950000 mV): -110
[ 3019.762469] drm_client_modeset_commit_atomic+0x230/0x2a0
[ 3019.771021] cpu cpu0: Failed to set regulator voltages: -110
[ 3019.776384] drm_client_modeset_commit_locked+0x68/0x1d0
[ 3019.776395] drm_client_modeset_commit+0x38/0x60
[ 3019.776405] drm_fbdev_client_restore+0x80/0xe0
[ 3019.782090] cpufreq: __target_index: Failed to change cpu frequency: -110
[ 3019.787367] drm_client_dev_restore+0xa0/0x110
[ 3019.787375] drm_lastclose+0x40/0xb0
[ 3019.811317] drm_release+0x16c/0x190
[ 3019.814899] __fput+0x78/0x260
[ 3019.817961] ____fput+0x18/0x30
[ 3019.821109] task_work_run+0x88/0xe0
[ 3019.824689] do_notify_resume+0x20c/0x1430
[ 3019.828795] el0_svc+0x120/0x130
[ 3019.832030] el0t_64_sync_handler+0xbc/0x140
[ 3019.836305] el0t_64_sync+0x18c/0x190
As far as I can tell, I haven't encountered the same with gpcv2, but
your analysis seems correct. I'll carry this patch in my tree for a
while to test it.
> 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/gpcv2.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/soc/imx/gpcv2.c b/drivers/soc/imx/gpcv2.c
> index 88aee59730e39..ee9294ad25ba1 100644
> --- a/drivers/soc/imx/gpcv2.c
> +++ b/drivers/soc/imx/gpcv2.c
> @@ -319,10 +319,16 @@ static int imx_pgc_power_up(struct generic_pm_domain *genpd)
> u32 reg_val, pgc;
> int ret;
>
> + ret = clk_bulk_prepare(domain->num_clks, domain->clks);
> + if (ret) {
> + dev_err(domain->dev, "failed to prepare reset clocks\n");
> + return ret;
> + }
> +
> ret = pm_runtime_get_sync(domain->dev);
> if (ret < 0) {
> pm_runtime_put_noidle(domain->dev);
> - return ret;
> + goto out_clock_unprepare;
> }
>
> if (!IS_ERR(domain->regulator)) {
> @@ -338,7 +344,7 @@ static int imx_pgc_power_up(struct generic_pm_domain *genpd)
> reset_control_assert(domain->reset);
>
> /* Enable reset clocks for all devices in the domain */
> - ret = clk_bulk_prepare_enable(domain->num_clks, domain->clks);
> + ret = clk_bulk_enable(domain->num_clks, domain->clks);
> if (ret) {
> dev_err(domain->dev, "failed to enable reset clocks\n");
> goto out_regulator_disable;
> @@ -402,12 +408,14 @@ static int imx_pgc_power_up(struct generic_pm_domain *genpd)
> return 0;
>
> out_clk_disable:
> - clk_bulk_disable_unprepare(domain->num_clks, domain->clks);
> + clk_bulk_disable(domain->num_clks, domain->clks);
> out_regulator_disable:
> if (!IS_ERR(domain->regulator))
> regulator_disable(domain->regulator);
> out_put_pm:
> pm_runtime_put(domain->dev);
> +out_clock_unprepare:
> + clk_bulk_unprepare(domain->num_clks, domain->clks);
>
> return ret;
> }
--
Regards,
Laurent Pinchart
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