From a41980f2a3eb33ed7a2636e83498b47e95ceb05b Mon Sep 17 00:00:00 2001 From: Marek Szyprowski Date: Thu, 21 Apr 2016 07:58:35 +0100 Subject: ARM: 8566/1: drivers: amba: properly handle devices with power domains To read pid/cid registers, the probed device need to be properly turned on. When it is inside a power domain, the bus code should ensure that the given power domain is enabled before trying to access device's registers. However in some cases power domain (or clocks) might not be yet available. Returning -EPROBE_DEFER is not a solution in such case, because callers don't handle this special error code. Instead such devices are added to the special list and their registration is retried from periodic worker until all resources are available. Signed-off-by: Marek Szyprowski Signed-off-by: Russell King --- drivers/amba/bus.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 90 insertions(+), 10 deletions(-) diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c index f0099360039e..a5b5c87e2114 100644 --- a/drivers/amba/bus.c +++ b/drivers/amba/bus.c @@ -336,16 +336,7 @@ static void amba_device_release(struct device *dev) kfree(d); } -/** - * amba_device_add - add a previously allocated AMBA device structure - * @dev: AMBA device allocated by amba_device_alloc - * @parent: resource parent for this devices resources - * - * Claim the resource, and read the device cell ID if not already - * initialized. Register the AMBA device with the Linux device - * manager. - */ -int amba_device_add(struct amba_device *dev, struct resource *parent) +static int amba_device_try_add(struct amba_device *dev, struct resource *parent) { u32 size; void __iomem *tmp; @@ -373,6 +364,12 @@ int amba_device_add(struct amba_device *dev, struct resource *parent) goto err_release; } + ret = dev_pm_domain_attach(&dev->dev, true); + if (ret == -EPROBE_DEFER) { + iounmap(tmp); + goto err_release; + } + ret = amba_get_enable_pclk(dev); if (ret == 0) { u32 pid, cid; @@ -398,6 +395,7 @@ int amba_device_add(struct amba_device *dev, struct resource *parent) } iounmap(tmp); + dev_pm_domain_detach(&dev->dev, true); if (ret) goto err_release; @@ -421,6 +419,88 @@ int amba_device_add(struct amba_device *dev, struct resource *parent) err_out: return ret; } + +/* + * Registration of AMBA device require reading its pid and cid registers. + * To do this, the device must be turned on (if it is a part of power domain) + * and have clocks enabled. However in some cases those resources might not be + * yet available. Returning EPROBE_DEFER is not a solution in such case, + * because callers don't handle this special error code. Instead such devices + * are added to the special list and their registration is retried from + * periodic worker, until all resources are available and registration succeeds. + */ +struct deferred_device { + struct amba_device *dev; + struct resource *parent; + struct list_head node; +}; + +static LIST_HEAD(deferred_devices); +static DEFINE_MUTEX(deferred_devices_lock); + +static void amba_deferred_retry_func(struct work_struct *dummy); +static DECLARE_DELAYED_WORK(deferred_retry_work, amba_deferred_retry_func); + +#define DEFERRED_DEVICE_TIMEOUT (msecs_to_jiffies(5 * 1000)) + +static void amba_deferred_retry_func(struct work_struct *dummy) +{ + struct deferred_device *ddev, *tmp; + + mutex_lock(&deferred_devices_lock); + + list_for_each_entry_safe(ddev, tmp, &deferred_devices, node) { + int ret = amba_device_try_add(ddev->dev, ddev->parent); + + if (ret == -EPROBE_DEFER) + continue; + + list_del_init(&ddev->node); + kfree(ddev); + } + + if (!list_empty(&deferred_devices)) + schedule_delayed_work(&deferred_retry_work, + DEFERRED_DEVICE_TIMEOUT); + + mutex_unlock(&deferred_devices_lock); +} + +/** + * amba_device_add - add a previously allocated AMBA device structure + * @dev: AMBA device allocated by amba_device_alloc + * @parent: resource parent for this devices resources + * + * Claim the resource, and read the device cell ID if not already + * initialized. Register the AMBA device with the Linux device + * manager. + */ +int amba_device_add(struct amba_device *dev, struct resource *parent) +{ + int ret = amba_device_try_add(dev, parent); + + if (ret == -EPROBE_DEFER) { + struct deferred_device *ddev; + + ddev = kmalloc(sizeof(*ddev), GFP_KERNEL); + if (!ddev) + return -ENOMEM; + + ddev->dev = dev; + ddev->parent = parent; + ret = 0; + + mutex_lock(&deferred_devices_lock); + + if (list_empty(&deferred_devices)) + schedule_delayed_work(&deferred_retry_work, + DEFERRED_DEVICE_TIMEOUT); + list_add_tail(&ddev->node, &deferred_devices); + + mutex_unlock(&deferred_devices_lock); + } + return ret; +} EXPORT_SYMBOL_GPL(amba_device_add); static struct amba_device * -- cgit v1.2.3