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

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