linux-kernel - Re: [PATCH] usb: Probe EHCI, OHCI controllers asynchronously

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Date:   Wed, 18 May 2022 20:41:58 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, Dmitry Torokhov <dtor@...omium.org>,
        linux-usb@...r.kernel.org, Doug Anderson <dianders@...omium.org>
Subject: Re: [PATCH] usb: Probe EHCI, OHCI controllers asynchronously

On Wed, May 18, 2022 at 03:02:51PM -0700, Brian Norris wrote:
> From: Dmitry Torokhov <dtor@...omium.org>
> 
> initcall_debug shows that OHCI controllers take ~60ms to probe on
> Rockchip RK3399 systems:
> 
>   probe of fe3a0000.usb returned 1 after 58941 usecs
> 
> A few of these can add up to waste non-trivial amounts of time at boot.
> 
> These host controllers don't provide resources to other drivers, so
> this shouldn't contribute to exposing race conditions.
> 
> Chrome OS kernels have carried this patch on some systems for a while
> without issues. Similar patches have been merged for a variety of (e)MMC
> host controllers for similar reasons.
> 
> Signed-off-by: Dmitry Torokhov <dtor@...omium.org>
> [Brian: rewrote commit message, refreshed, but retained dtor's original
>  authorship ]
> Signed-off-by: Brian Norris <briannorris@...omium.org>
> ---

Acked-by: Alan Stern <stern@...land.harvard.edu>

>  drivers/usb/host/ehci-platform.c | 1 +
>  drivers/usb/host/ohci-platform.c | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/drivers/usb/host/ehci-platform.c b/drivers/usb/host/ehci-platform.c
> index 1115431a255d..f343967443e2 100644
> --- a/drivers/usb/host/ehci-platform.c
> +++ b/drivers/usb/host/ehci-platform.c
> @@ -518,6 +518,7 @@ static struct platform_driver ehci_platform_driver = {
>  		.pm	= pm_ptr(&ehci_platform_pm_ops),
>  		.of_match_table = vt8500_ehci_ids,
>  		.acpi_match_table = ACPI_PTR(ehci_acpi_match),
> +		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
>  	}
>  };
>  
> diff --git a/drivers/usb/host/ohci-platform.c b/drivers/usb/host/ohci-platform.c
> index 4a8456f12a73..47dfbfe9e519 100644
> --- a/drivers/usb/host/ohci-platform.c
> +++ b/drivers/usb/host/ohci-platform.c
> @@ -334,6 +334,7 @@ static struct platform_driver ohci_platform_driver = {
>  		.name	= "ohci-platform",
>  		.pm	= &ohci_platform_pm_ops,
>  		.of_match_table = ohci_platform_ids,
> +		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
>  	}
>  };
>  
> -- 
> 2.36.1.124.g0e6072fb45-goog
>