[PATCH v1] dd: Invoke one probe retry cycle after some initcall levels

[PATCH v1] dd: Invoke one probe retry cycle after some initcall levels

[Rishabh Bhatnagar]

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.

Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
---

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.

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

Re: [PATCH v1] dd: Invoke one probe retry cycle after some initcall levels

[Rafael J. Wysocki]

On Fri, Aug 10, 2018 at 11:52 PM Rishabh Bhatnagar
<rishabhb@codeaurora.org> wrote:
>
> 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.
>
> Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>
> Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
> ---
>
> 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.

Please move the above to the changelog proper (ie. above the tags) and
resend the patch with CCs to linux-pm@vger.kernel.org and LKML.

Thanks,
Rafael

[PATCH v1] dd: Invoke one probe retry cycle after some initcall levels

[Rishabh Bhatnagar]

From: Rishabh Bhatnagar <rishabhb@codeaurora.org>

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 <markivx@codeaurora.org>
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
---

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

Re: [PATCH v1] dd: Invoke one probe retry cycle after some initcall levels

[rishabhb]

On 2018-08-13 10:39, Rishabh Bhatnagar wrote:
> From: Rishabh Bhatnagar <rishabhb@codeaurora.org>
> 
> 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 <markivx@codeaurora.org>
> Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
> ---
> 
> 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

Re: [PATCH v1] dd: Invoke one probe retry cycle after some initcall levels

[Rafael J. Wysocki]

On Mon, Aug 13, 2018 at 7:40 PM Rishabh Bhatnagar <rishabhb@quicinc.com> wrote:
>
> From: Rishabh Bhatnagar <rishabhb@codeaurora.org>
>
> 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 <markivx@codeaurora.org>
> Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
> ---
>
> 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