Re: [PATCH 3/3] drm/exynos: move Exynos platform drivers registration to init

On 2014년 11월 21일 08:42, Gustavo Padovan wrote:

From: Gustavo Padovan gustavo.padovan@collabora.co.uk

Registering the Exynos DRM subdevices platform drivers in the probe function is causing an infinite loop. Fix this by moving it to the exynos_drm_init() function to register the drivers on module init.

Registering drivers in the probe functions causes a deadlock in the parent device lock. See Grant Likely explanation on the topic:

"I think the problem is that exynos_drm_init() is registering a normal (non-OF) platform device, so the parent will be /sys/devices/platform. It immediately gets bound against exynos_drm_platform_driver which calls the exynos drm_platform_probe() hook. The driver core obtains device_lock() on the device *and on the device parent*.

Inside the probe hook, additional platform_drivers get registered. Each time one does, it tries to bind against every platform device in the system, which includes the ones created by OF. When it attempts to bind, it obtains device_lock() on the device *and on the device parent*.

Before the change to move of-generated platform devices into /sys/devices/platform, the devices had different parents. Now both devices have /sys/devices/platform as the parent, so yes they are going to deadlock.

The real problem is registering drivers from within a probe hook. That is completely wrong for the above deadlock reason. __driver_attach() will deadlock. Those registrations must be pulled out of .probe().

Registering devices in .probe() is okay because __device_attach() doesn't try to obtain device_lock() on the parent."

INFO: task swapper/0:1 blocked for more than 120 seconds. Not tainted 3.18.0-rc3-next-20141105 #794 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. swapper/0 D c052534c 0 1 0 0x00000000 [<c052534c>] (__schedule) from [<c0525b34>] (schedule_preempt_disabled+0x14/0x20) [<c0525b34>] (schedule_preempt_disabled) from [<c0526d44>] (mutex_lock_nested+0x1c4/0x464

[<c0526d44>] (mutex_lock_nested) from [<c02be908>] (__driver_attach+0x48/0x98) [<c02be908>] (__driver_attach) from [<c02bcc00>] (bus_for_each_dev+0x54/0x88) [<c02bcc00>] (bus_for_each_dev) from [<c02bdce0>] (bus_add_driver+0xe4/0x200) [<c02bdce0>] (bus_add_driver) from [<c02bef94>] (driver_register+0x78/0xf4) [<c02bef94>] (driver_register) from [<c029e99c>] (exynos_drm_platform_probe+0x34/0x234) [<c029e99c>] (exynos_drm_platform_probe) from [<c02bfcf0>] (platform_drv_probe+0x48/0xa4) [<c02bfcf0>] (platform_drv_probe) from [<c02be680>] (driver_probe_device+0x13c/0x37c) [<c02be680>] (driver_probe_device) from [<c02be954>] (__driver_attach+0x94/0x98) [<c02be954>] (__driver_attach) from [<c02bcc00>] (bus_for_each_dev+0x54/0x88) [<c02bcc00>] (bus_for_each_dev) from [<c02bdce0>] (bus_add_driver+0xe4/0x200) [<c02bdce0>] (bus_add_driver) from [<c02bef94>] (driver_register+0x78/0xf4) [<c02bef94>] (driver_register) from [<c029e938>] (exynos_drm_init+0x70/0xa0) [<c029e938>] (exynos_drm_init) from [<c00089b0>] (do_one_initcall+0xac/0x1f0) [<c00089b0>] (do_one_initcall) from [<c074bd90>] (kernel_init_freeable+0x10c/0x1d8) [<c074bd90>] (kernel_init_freeable) from [<c051eabc>] (kernel_init+0x8/0xec) [<c051eabc>] (kernel_init) from [<c000f268>] (ret_from_fork+0x14/0x2c) 3 locks held by swapper/0/1: #0: (&dev->mutex){......}, at: [<c02be908>] __driver_attach+0x48/0x98 #1: (&dev->mutex){......}, at: [<c02be918>] __driver_attach+0x58/0x98 #2: (&dev->mutex){......}, at: [<c02be908>] __driver_attach+0x48/0x98

Signed-off-by: Javier Martinez Canillas javier.martinez@collabora.co.uk Signed-off-by: Gustavo Padovan gustavo.padovan@collabora.co.uk

---

drivers/gpu/drm/exynos/exynos_drm_drv.c | 124 +++++++++++++++----------------- 1 file changed, 59 insertions(+), 65 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.c b/drivers/gpu/drm/exynos/exynos_drm_drv.c index 91891cf..cb3ed9b 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_drv.c +++ b/drivers/gpu/drm/exynos/exynos_drm_drv.c @@ -548,6 +548,38 @@ static const struct component_master_ops exynos_drm_ops = { .unbind = exynos_drm_unbind, };

+static int exynos_drm_platform_probe(struct platform_device *pdev) +{

• struct component_match *match;
• pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
• exynos_drm_driver.num_ioctls = ARRAY_SIZE(exynos_ioctls);
• match = exynos_drm_match_add(&pdev->dev);
• if (IS_ERR(match)) {

• return PTR_ERR(match);
  

• }
• return component_master_add_with_match(&pdev->dev, &exynos_drm_ops,

• 			       match);
  

+}

+static int exynos_drm_platform_remove(struct platform_device *pdev) +{

• component_master_del(&pdev->dev, &exynos_drm_ops);
• return 0;

+}

+static struct platform_driver exynos_drm_platform_driver = {

• .probe = exynos_drm_platform_probe,
• .remove = exynos_drm_platform_remove,
• .driver = {

• .owner	= THIS_MODULE,
  

• .name	= "exynos-drm",
  

• .pm	= &exynos_drm_pm_ops,
  

• },

+};

static struct platform_driver *const exynos_drm_kms_drivers[] = { #ifdef CONFIG_DRM_EXYNOS_FIMD &fimd_driver, @@ -582,13 +614,24 @@ static struct platform_driver *const exynos_drm_non_kms_drivers[] = { #endif };

-static int exynos_drm_platform_probe(struct platform_device *pdev) +static int exynos_drm_init(void) {

• struct component_match *match; int ret, i, j;

• pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);

• exynos_drm_driver.num_ioctls = ARRAY_SIZE(exynos_ioctls);

• exynos_drm_pdev = platform_device_register_simple("exynos-drm", -1,

• 						NULL, 0);
  

• if (IS_ERR(exynos_drm_pdev))

• return PTR_ERR(exynos_drm_pdev);
  

+#ifdef CONFIG_DRM_EXYNOS_VIDI

• ret = exynos_drm_probe_vidi();
• if (ret < 0)

• goto err_unregister_pd;
  

+#endif

If vidi driver is enabled then Exynos drm driver doesn't work.

• ret = platform_driver_register(&exynos_drm_platform_driver);
• if (ret)

• goto err_remove_vidi;
  

Above platform_driver_register should be called after all kms and non-kms drivers are registered. And your patch should be re-based on top of exynos-drm-next.

I just re-based it on top of exynos-drm-next and changed the platform_driver_register to be called at the end.

Thanks, Inki Dae

for (i = 0; i < ARRAY_SIZE(exynos_drm_kms_drivers); ++i) { ret = platform_driver_register(exynos_drm_kms_drivers[i]); @@ -596,26 +639,17 @@ static int exynos_drm_platform_probe(struct platform_device *pdev) goto err_unregister_kms_drivers; }

• match = exynos_drm_match_add(&pdev->dev);
• if (IS_ERR(match)) {

• ret = PTR_ERR(match);
  

• goto err_unregister_kms_drivers;
  

• }
• ret = component_master_add_with_match(&pdev->dev, &exynos_drm_ops,

• 				match);
  

• if (ret < 0)

• goto err_unregister_kms_drivers;
  

• for (j = 0; j < ARRAY_SIZE(exynos_drm_non_kms_drivers); ++j) { ret = platform_driver_register(exynos_drm_non_kms_drivers[j]); if (ret < 0)

• 	goto err_del_component_master;
  

• 	goto err_unregister_non_kms_drivers;
  

  }

+#ifdef CONFIG_DRM_EXYNOS_IPP ret = exynos_platform_device_ipp_register(); if (ret < 0) goto err_unregister_non_kms_drivers; +#endif

return ret;

@@ -626,17 +660,22 @@ err_unregister_non_kms_drivers: while (--j >= 0) platform_driver_unregister(exynos_drm_non_kms_drivers[j]);

-err_del_component_master:

• component_master_del(&pdev->dev, &exynos_drm_ops);

err_unregister_kms_drivers: while (--i >= 0) platform_driver_unregister(exynos_drm_kms_drivers[i]);

+err_remove_vidi: +#ifdef CONFIG_DRM_EXYNOS_VIDI

• exynos_drm_remove_vidi();

+err_unregister_pd: +#endif

• platform_device_unregister(exynos_drm_pdev);
• return ret;

}

-static int exynos_drm_platform_remove(struct platform_device *pdev) +static void exynos_drm_exit(void) { int i;

@@ -647,54 +686,9 @@ static int exynos_drm_platform_remove(struct platform_device *pdev) for (i = ARRAY_SIZE(exynos_drm_non_kms_drivers) - 1; i >= 0; --i) platform_driver_unregister(exynos_drm_non_kms_drivers[i]);

• component_master_del(&pdev->dev, &exynos_drm_ops);

• for (i = ARRAY_SIZE(exynos_drm_kms_drivers) - 1; i >= 0; --i) platform_driver_unregister(exynos_drm_kms_drivers[i]);

• return 0;

-}

-static struct platform_driver exynos_drm_platform_driver = {

• .probe = exynos_drm_platform_probe,
• .remove = exynos_drm_platform_remove,
• .driver = {

• .owner	= THIS_MODULE,
  

• .name	= "exynos-drm",
  

• .pm	= &exynos_drm_pm_ops,
  

• },

-};

-static int exynos_drm_init(void) -{

• int ret;
• exynos_drm_pdev = platform_device_register_simple("exynos-drm", -1,

• 						NULL, 0);
  

• if (IS_ERR(exynos_drm_pdev))

• return PTR_ERR(exynos_drm_pdev);
  

• ret = exynos_drm_probe_vidi();
• if (ret < 0)

• goto err_unregister_pd;
  

• ret = platform_driver_register(&exynos_drm_platform_driver);
• if (ret)

• goto err_remove_vidi;
  

• return 0;

-err_remove_vidi:

• exynos_drm_remove_vidi();

-err_unregister_pd:

• platform_device_unregister(exynos_drm_pdev);
• return ret;

-}

-static void exynos_drm_exit(void) -{ platform_driver_unregister(&exynos_drm_platform_driver);

exynos_drm_remove_vidi();