[PATCH v4] clk: mediatek: Do a runtime PM get on controllers during probe

[PATCH v4] clk: mediatek: Do a runtime PM get on controllers during probe

[Pin-yen Lin]

mt8183-mfgcfg has a mutual dependency with genpd during the probing
stage, which leads to a deadlock in the following call stack:

CPU0:  genpd_lock --> clk_prepare_lock
genpd_power_off_work_fn()
 genpd_lock()
 generic_pm_domain::power_off()
    clk_unprepare()
      clk_prepare_lock()

CPU1: clk_prepare_lock --> genpd_lock
clk_register()
  __clk_core_init()
    clk_prepare_lock()
    clk_pm_runtime_get()
      genpd_lock()

Do a runtime PM get at the probe function to make sure clk_register()
won't acquire the genpd lock. Instead of only modifying mt8183-mfgcfg,
do this on all mediatek clock controller probings because we don't
believe this would cause any regression.

Verified on MT8183 and MT8192 Chromebooks.

Fixes: acddfc2c261b ("clk: mediatek: Add MT8183 clock support")
Signed-off-by: Pin-yen Lin <treapking@chromium.org>

---
v3: https://lore.kernel.org/all/20240108081834.408403-1-treapking@chromium.org/

Changes in v4:
- Remove the need_runtime_pm flag and apply this to all mtk controllers

Changes in v3:
- Update the commit message and the comments before runtime PM call

Changes in v2:
- Fix the order of error handling
- Update the commit message and add a comment before the runtime PM call

 drivers/clk/mediatek/clk-mtk.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/clk/mediatek/clk-mtk.c b/drivers/clk/mediatek/clk-mtk.c
index 2e55368dc4d8..bd37ab4d1a9b 100644
--- a/drivers/clk/mediatek/clk-mtk.c
+++ b/drivers/clk/mediatek/clk-mtk.c
@@ -13,6 +13,7 @@
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 #include <linux/slab.h>
 
 #include "clk-mtk.h"
@@ -494,6 +495,16 @@ static int __mtk_clk_simple_probe(struct platform_device *pdev,
 			return IS_ERR(base) ? PTR_ERR(base) : -ENOMEM;
 	}
 
+
+	devm_pm_runtime_enable(&pdev->dev);
+	/*
+	 * Do a pm_runtime_resume_and_get() to workaround a possible
+	 * deadlock between clk_register() and the genpd framework.
+	 */
+	r = pm_runtime_resume_and_get(&pdev->dev);
+	if (r)
+		return r;
+
 	/* Calculate how many clk_hw_onecell_data entries to allocate */
 	num_clks = mcd->num_clks + mcd->num_composite_clks;
 	num_clks += mcd->num_fixed_clks + mcd->num_factor_clks;
@@ -574,6 +585,8 @@ static int __mtk_clk_simple_probe(struct platform_device *pdev,
 			goto unregister_clks;
 	}
 
+	pm_runtime_put(&pdev->dev);
+
 	return r;
 
 unregister_clks:
@@ -604,6 +617,8 @@ static int __mtk_clk_simple_probe(struct platform_device *pdev,
 free_base:
 	if (mcd->shared_io && base)
 		iounmap(base);
+
+	pm_runtime_put(&pdev->dev);
 	return r;
 }
 
-- 
2.44.0.278.ge034bb2e1d-goog

Re: [PATCH v4] clk: mediatek: Do a runtime PM get on controllers during probe

[AngeloGioacchino Del Regno]

Il 12/03/24 12:51, Pin-yen Lin ha scritto:
> mt8183-mfgcfg has a mutual dependency with genpd during the probing
> stage, which leads to a deadlock in the following call stack:
> 
> CPU0:  genpd_lock --> clk_prepare_lock
> genpd_power_off_work_fn()
>   genpd_lock()
>   generic_pm_domain::power_off()
>      clk_unprepare()
>        clk_prepare_lock()
> 
> CPU1: clk_prepare_lock --> genpd_lock
> clk_register()
>    __clk_core_init()
>      clk_prepare_lock()
>      clk_pm_runtime_get()
>        genpd_lock()
> 
> Do a runtime PM get at the probe function to make sure clk_register()
> won't acquire the genpd lock. Instead of only modifying mt8183-mfgcfg,
> do this on all mediatek clock controller probings because we don't
> believe this would cause any regression.
> 
> Verified on MT8183 and MT8192 Chromebooks.
> 
> Fixes: acddfc2c261b ("clk: mediatek: Add MT8183 clock support")
> Signed-off-by: Pin-yen Lin <treapking@chromium.org>
> 

MT8195 Cherry Tomato - no issues as well.

Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Re: [PATCH v4] clk: mediatek: Do a runtime PM get on controllers during probe

[Stephen Boyd]

Quoting Pin-yen Lin (2024-03-12 04:51:55)
> mt8183-mfgcfg has a mutual dependency with genpd during the probing
> stage, which leads to a deadlock in the following call stack:
> 
> CPU0:  genpd_lock --> clk_prepare_lock
> genpd_power_off_work_fn()
>  genpd_lock()
>  generic_pm_domain::power_off()
>     clk_unprepare()
>       clk_prepare_lock()
> 
> CPU1: clk_prepare_lock --> genpd_lock
> clk_register()
>   __clk_core_init()
>     clk_prepare_lock()
>     clk_pm_runtime_get()
>       genpd_lock()
> 
> Do a runtime PM get at the probe function to make sure clk_register()
> won't acquire the genpd lock. Instead of only modifying mt8183-mfgcfg,
> do this on all mediatek clock controller probings because we don't
> believe this would cause any regression.
> 
> Verified on MT8183 and MT8192 Chromebooks.
> 
> Fixes: acddfc2c261b ("clk: mediatek: Add MT8183 clock support")
> Signed-off-by: Pin-yen Lin <treapking@chromium.org>
> 
> ---

Applied to clk-fixes