From: Rishabh Bhatnagar <[email protected]>
Drivers that are registered at an initcall level may have to
wait until late_init before the probe deferral mechanism can
retry their probe functions. It is possible that their
dependencies were resolved much earlier, in some cases even
before the next initcall level. Invoke one probe retry cycle
at every _sync initcall level after subsys initcall, allowing
these drivers to be probed earlier.
To give an example many Qualcomm drivers are dependent on the
regulator and bus driver. Both the regulator and bus driver
are probed in the subsys_initcall level. Now the probe of bus
driver requires regulator to be working. If the probe of bus
driver happens before regulator, then bus driver's probe will
be deferred and all other device's probes which depend on bus
driver will also be deferred.
The impact of this problem is reduced if we have this patch.
Signed-off-by: Vikram Mulukutla <[email protected]>
Signed-off-by: Rishabh Bhatnagar <[email protected]>
---
Changes since v0:
* Remove arch_initcall_sync(deferred_probe_initcall) from patch. This is not
really needed as none of the devices are re-probed in arch_initcall_sync
level.
drivers/base/dd.c | 32 ++++++++++++++++++++++++++------
1 file changed, 26 insertions(+), 6 deletions(-)
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 1435d72..9aa41aa 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -224,23 +224,43 @@ void device_unblock_probing(void)
driver_deferred_probe_trigger();
}
+static void enable_trigger_defer_cycle(void)
+{
+ driver_deferred_probe_enable = true;
+ driver_deferred_probe_trigger();
+ /*
+ * Sort as many dependencies as possible before the next initcall
+ * level
+ */
+ flush_work(&deferred_probe_work);
+}
+
/**
* deferred_probe_initcall() - Enable probing of deferred devices
*
* We don't want to get in the way when the bulk of drivers are getting probed.
* Instead, this initcall makes sure that deferred probing is delayed until
- * late_initcall time.
+ * all the registered initcall functions at a particular level are completed.
+ * This function is invoked at every *_initcall_sync level.
*/
static int deferred_probe_initcall(void)
{
- driver_deferred_probe_enable = true;
- driver_deferred_probe_trigger();
- /* Sort as many dependencies as possible before exiting initcalls */
- flush_work(&deferred_probe_work);
+ enable_trigger_defer_cycle();
+ driver_deferred_probe_enable = false;
+ return 0;
+}
+subsys_initcall_sync(deferred_probe_initcall);
+fs_initcall_sync(deferred_probe_initcall);
+device_initcall_sync(deferred_probe_initcall);
+
+static int deferred_probe_enable_fn(void)
+{
+ /* Enable deferred probing for all time */
+ enable_trigger_defer_cycle();
initcalls_done = true;
return 0;
}
-late_initcall(deferred_probe_initcall);
+late_initcall(deferred_probe_enable_fn);
/**
* device_is_bound() - Check if device is bound to a driver
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
On 2018-08-13 10:39, Rishabh Bhatnagar wrote:
> From: Rishabh Bhatnagar <[email protected]>
>
> Drivers that are registered at an initcall level may have to
> wait until late_init before the probe deferral mechanism can
> retry their probe functions. It is possible that their
> dependencies were resolved much earlier, in some cases even
> before the next initcall level. Invoke one probe retry cycle
> at every _sync initcall level after subsys initcall, allowing
> these drivers to be probed earlier.
> To give an example many Qualcomm drivers are dependent on the
> regulator and bus driver. Both the regulator and bus driver
> are probed in the subsys_initcall level. Now the probe of bus
> driver requires regulator to be working. If the probe of bus
> driver happens before regulator, then bus driver's probe will
> be deferred and all other device's probes which depend on bus
> driver will also be deferred.
> The impact of this problem is reduced if we have this patch.
>
> Signed-off-by: Vikram Mulukutla <[email protected]>
> Signed-off-by: Rishabh Bhatnagar <[email protected]>
> ---
>
> Changes since v0:
> * Remove arch_initcall_sync(deferred_probe_initcall) from patch. This
> is not
> really needed as none of the devices are re-probed in
> arch_initcall_sync
> level.
>
> drivers/base/dd.c | 32 ++++++++++++++++++++++++++------
> 1 file changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 1435d72..9aa41aa 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -224,23 +224,43 @@ void device_unblock_probing(void)
> driver_deferred_probe_trigger();
> }
>
> +static void enable_trigger_defer_cycle(void)
> +{
> + driver_deferred_probe_enable = true;
> + driver_deferred_probe_trigger();
> + /*
> + * Sort as many dependencies as possible before the next initcall
> + * level
> + */
> + flush_work(&deferred_probe_work);
> +}
> +
> /**
> * deferred_probe_initcall() - Enable probing of deferred devices
> *
> * We don't want to get in the way when the bulk of drivers are
> getting probed.
> * Instead, this initcall makes sure that deferred probing is delayed
> until
> - * late_initcall time.
> + * all the registered initcall functions at a particular level are
> completed.
> + * This function is invoked at every *_initcall_sync level.
> */
> static int deferred_probe_initcall(void)
> {
> - driver_deferred_probe_enable = true;
> - driver_deferred_probe_trigger();
> - /* Sort as many dependencies as possible before exiting initcalls */
> - flush_work(&deferred_probe_work);
> + enable_trigger_defer_cycle();
> + driver_deferred_probe_enable = false;
> + return 0;
> +}
> +subsys_initcall_sync(deferred_probe_initcall);
> +fs_initcall_sync(deferred_probe_initcall);
> +device_initcall_sync(deferred_probe_initcall);
> +
> +static int deferred_probe_enable_fn(void)
> +{
> + /* Enable deferred probing for all time */
> + enable_trigger_defer_cycle();
> initcalls_done = true;
> return 0;
> }
> -late_initcall(deferred_probe_initcall);
> +late_initcall(deferred_probe_enable_fn);
>
> /**
> * device_is_bound() - Check if device is bound to a driver
Hi Rafael
Just a reminder about this patch. Let me know if you want me to add/edit
anything else.
-Rishabh
On Mon, Aug 13, 2018 at 7:40 PM Rishabh Bhatnagar <[email protected]> wrote:
>
> From: Rishabh Bhatnagar <[email protected]>
>
> Drivers that are registered at an initcall level may have to
> wait until late_init before the probe deferral mechanism can
> retry their probe functions. It is possible that their
> dependencies were resolved much earlier, in some cases even
> before the next initcall level. Invoke one probe retry cycle
> at every _sync initcall level after subsys initcall, allowing
> these drivers to be probed earlier.
> To give an example many Qualcomm drivers are dependent on the
> regulator and bus driver. Both the regulator and bus driver
> are probed in the subsys_initcall level. Now the probe of bus
> driver requires regulator to be working. If the probe of bus
> driver happens before regulator, then bus driver's probe will
> be deferred and all other device's probes which depend on bus
> driver will also be deferred.
> The impact of this problem is reduced if we have this patch.
>
> Signed-off-by: Vikram Mulukutla <[email protected]>
> Signed-off-by: Rishabh Bhatnagar <[email protected]>
> ---
>
> Changes since v0:
> * Remove arch_initcall_sync(deferred_probe_initcall) from patch. This is not
> really needed as none of the devices are re-probed in arch_initcall_sync
> level.
>
> drivers/base/dd.c | 32 ++++++++++++++++++++++++++------
> 1 file changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 1435d72..9aa41aa 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -224,23 +224,43 @@ void device_unblock_probing(void)
> driver_deferred_probe_trigger();
> }
>
> +static void enable_trigger_defer_cycle(void)
> +{
> + driver_deferred_probe_enable = true;
Isn't it sufficient to enable it once?
> + driver_deferred_probe_trigger();
> + /*
> + * Sort as many dependencies as possible before the next initcall
> + * level
> + */
> + flush_work(&deferred_probe_work);
> +}
I would call this function driver_deferred_probe_sync() or similar to
indicate that it is a synchronization point.
Thanks,
Rafael