| Message ID | 1460711612-5268-1-git-send-email-m.szyprowski@samsung.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On 15 April 2016 at 11:13, Marek Szyprowski <m.szyprowski@samsung.com> wrote: > 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 <m.szyprowski@samsung.com> > --- > Changelog: > > v8: > - replaced notifier with periodic workqueue on Greg request > > v7: https://lkml.org/lkml/2016/4/13/201 > - replaced late_initcall approach with a notifier registered to device core > > v6: https://lkml.org/lkml/2016/4/12/414 > - got back to v1-style approach on Russell King request to avoid ABI break > - use list for storing deferred devices and retry their registration from > late_initcall > > v5: https://lkml.org/lkml/2016/2/10/179 > - added 2 more patches to avoid regression with existing drivers (nvdimm and > sa1111), for more information, see https://lkml.org/lkml/2015/12/17/390 > - changed thread name to "AMBA: add complete support for power domains" > > v4: https://lkml.org/lkml/2015/12/2/52 > - fixed more issues pointed by Ulf Hansson and Russell King > > v3: https://lkml.org/lkml/2015/12/1/334 > - fixed issues pointed by Ulf Hansson > - dropped patch for exynos4210 dts, because it already got queued for merging > > v2: https://lkml.org/lkml/2015/11/26/229 > - added 2 patches from 'On-demand device probing' thread > (https://lkml.org/lkml/2015/9/29/189), which move PID/CIR reading > from amba_device_add() to amba_match() > - moved dev_pm_domain_attach() to amba_match(), which is allowed to > return -EPROBE_DEFER > > v1: http://www.spinics.net/lists/arm-kernel/msg463185.html > - initial version > --- > 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 * > -- > 1.9.2 > Overall this looks okay to me! Even if I don't really like the approach, it seems like this is the only viable option there is right now. One minor improvement that I could think of, is to use also a late initcall in conjunction with the delayed work. So, instead of scheduling a work unconditionally when -EPROBE_DEFER is returned from amba_device_try_add(), you can postpone the *first* re-try to be done from a late initcall. Of course, as devices may be added also after the late initcall, you need to keep a flag which tells amba_device_add() whether it can rely on the late initcall to re-try, or if it needs to schedule a work by itself. Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello, On 2016-04-25 11:19, Ulf Hansson wrote: > On 15 April 2016 at 11:13, Marek Szyprowski <m.szyprowski@samsung.com> wrote: >> 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 <m.szyprowski@samsung.com> >> --- >> Changelog: >> >> v8: >> - replaced notifier with periodic workqueue on Greg request >> >> v7: https://lkml.org/lkml/2016/4/13/201 >> - replaced late_initcall approach with a notifier registered to device core >> >> v6: https://lkml.org/lkml/2016/4/12/414 >> - got back to v1-style approach on Russell King request to avoid ABI break >> - use list for storing deferred devices and retry their registration from >> late_initcall >> >> v5: https://lkml.org/lkml/2016/2/10/179 >> - added 2 more patches to avoid regression with existing drivers (nvdimm and >> sa1111), for more information, see https://lkml.org/lkml/2015/12/17/390 >> - changed thread name to "AMBA: add complete support for power domains" >> >> v4: https://lkml.org/lkml/2015/12/2/52 >> - fixed more issues pointed by Ulf Hansson and Russell King >> >> v3: https://lkml.org/lkml/2015/12/1/334 >> - fixed issues pointed by Ulf Hansson >> - dropped patch for exynos4210 dts, because it already got queued for merging >> >> v2: https://lkml.org/lkml/2015/11/26/229 >> - added 2 patches from 'On-demand device probing' thread >> (https://lkml.org/lkml/2015/9/29/189), which move PID/CIR reading >> from amba_device_add() to amba_match() >> - moved dev_pm_domain_attach() to amba_match(), which is allowed to >> return -EPROBE_DEFER >> >> v1: http://www.spinics.net/lists/arm-kernel/msg463185.html >> - initial version >> --- >> 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 * >> -- >> 1.9.2 >> > Overall this looks okay to me! Even if I don't really like the > approach, it seems like this is the only viable option there is right > now. > > One minor improvement that I could think of, is to use also a late > initcall in conjunction with the delayed work. So, instead of > scheduling a work unconditionally when -EPROBE_DEFER is returned from > amba_device_try_add(), you can postpone the *first* re-try to be done > from a late initcall. > > Of course, as devices may be added also after the late initcall, you > need to keep a flag which tells amba_device_add() whether it can rely > on the late initcall to re-try, or if it needs to schedule a work by > itself. I don't think that such micro-optimization makes sense in this case. Please note that there is still no platform and driver which require this deferred probe logic - in my case exynos power domain driver is registered very early, so dev_pm_domain_attach() calls succeeds in the standard amba device registration path. This patch is mainly to get the device registered to power domain to properly read its cid/pid pair. Best regards
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 *
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 <m.szyprowski@samsung.com> --- Changelog: v8: - replaced notifier with periodic workqueue on Greg request v7: https://lkml.org/lkml/2016/4/13/201 - replaced late_initcall approach with a notifier registered to device core v6: https://lkml.org/lkml/2016/4/12/414 - got back to v1-style approach on Russell King request to avoid ABI break - use list for storing deferred devices and retry their registration from late_initcall v5: https://lkml.org/lkml/2016/2/10/179 - added 2 more patches to avoid regression with existing drivers (nvdimm and sa1111), for more information, see https://lkml.org/lkml/2015/12/17/390 - changed thread name to "AMBA: add complete support for power domains" v4: https://lkml.org/lkml/2015/12/2/52 - fixed more issues pointed by Ulf Hansson and Russell King v3: https://lkml.org/lkml/2015/12/1/334 - fixed issues pointed by Ulf Hansson - dropped patch for exynos4210 dts, because it already got queued for merging v2: https://lkml.org/lkml/2015/11/26/229 - added 2 patches from 'On-demand device probing' thread (https://lkml.org/lkml/2015/9/29/189), which move PID/CIR reading from amba_device_add() to amba_match() - moved dev_pm_domain_attach() to amba_match(), which is allowed to return -EPROBE_DEFER v1: http://www.spinics.net/lists/arm-kernel/msg463185.html - initial version --- drivers/amba/bus.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 90 insertions(+), 10 deletions(-)