linux-kernel - Re: [PATCH] usb: host: ohci-at91: suspend/resume ports after/before OHCI accesses

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Message-ID: <21280c02-0dd2-461a-1baf-464f280d2f0e@microchip.com>
Date:   Wed, 9 Jun 2021 14:40:19 +0200
From:   Nicolas Ferre <nicolas.ferre@...rochip.com>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>,
        <stern@...land.harvard.edu>, <gregkh@...uxfoundation.org>,
        <alexandre.belloni@...tlin.com>, <ludovic.desroches@...rochip.com>,
        <cristian.birsan@...rochip.com>
CC:     <linux-usb@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: host: ohci-at91: suspend/resume ports after/before
 OHCI accesses

On 09/06/2021 at 14:10, Claudiu Beznea wrote:
> On SAMA7G5 suspending ports will cut the access to OHCI registers and
> any subsequent access to them will lead to CPU being blocked trying to
> access that memory. Same thing happens on resume: if OHCI memory is
> accessed before resuming ports the CPU will block on that access. The
> OCHI memory is accessed on suspend/resume though
> ohci_suspend()/ohci_resume().
> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>

Claudiu,

Your patch look good to me.

In addition, I see ohci_at91_port_suspend() function also used in 
ohci_at91_hub_control(). It might suffer the same problem as I see 
accesses to ohci register, at first glance.

Can you please double check that we are not in such condition with calls 
to ohci_at91_hub_control()?

Best regards,
   Nicolas


> ---
> 
> The patch was tested on SAMA7G5, SAMA5D2 and SAM9X60.
> 
> Thank you,
> Claudiu Beznea
> 
>   drivers/usb/host/ohci-at91.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/host/ohci-at91.c b/drivers/usb/host/ohci-at91.c
> index b3a6a497dcb1..7c6202b05ff4 100644
> --- a/drivers/usb/host/ohci-at91.c
> +++ b/drivers/usb/host/ohci-at91.c
> @@ -666,8 +666,6 @@ ohci_hcd_at91_drv_suspend(struct device *dev)
>   	if (ohci_at91->wakeup)
>   		enable_irq_wake(hcd->irq);
>   
> -	ohci_at91_port_suspend(ohci_at91, 1);
> -
>   	ret = ohci_suspend(hcd, ohci_at91->wakeup);
>   	if (ret) {
>   		if (ohci_at91->wakeup)
> @@ -687,7 +685,10 @@ ohci_hcd_at91_drv_suspend(struct device *dev)
>   		/* flush the writes */
>   		(void) ohci_readl (ohci, &ohci->regs->control);
>   		msleep(1);
> +		ohci_at91_port_suspend(ohci_at91, 1);
>   		at91_stop_clock(ohci_at91);
> +	} else {
> +		ohci_at91_port_suspend(ohci_at91, 1);
>   	}
>   
>   	return ret;
> @@ -699,6 +700,8 @@ ohci_hcd_at91_drv_resume(struct device *dev)
>   	struct usb_hcd	*hcd = dev_get_drvdata(dev);
>   	struct ohci_at91_priv *ohci_at91 = hcd_to_ohci_at91_priv(hcd);
>   
> +	ohci_at91_port_suspend(ohci_at91, 0);
> +
>   	if (ohci_at91->wakeup)
>   		disable_irq_wake(hcd->irq);
>   	else
> @@ -706,8 +709,6 @@ ohci_hcd_at91_drv_resume(struct device *dev)
>   
>   	ohci_resume(hcd, false);
>   
> -	ohci_at91_port_suspend(ohci_at91, 0);
> -
>   	return 0;
>   }
>   
> 


-- 
Nicolas Ferre