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

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Message-ID: <7442ab4a-cb23-efa2-6f8f-6806028a752e@microchip.com>
Date:   Thu, 24 Jun 2021 06:54:09 +0000
From:   <Claudiu.Beznea@...rochip.com>
To:     <stern@...land.harvard.edu>
CC:     <gregkh@...uxfoundation.org>, <Nicolas.Ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <Ludovic.Desroches@...rochip.com>,
        <Cristian.Birsan@...rochip.com>, <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 24.06.2021 09:40, Claudiu Beznea - M18063 wrote:
> On 23.06.2021 19:41, Alan Stern wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> On Wed, Jun 23, 2021 at 02:33:14PM +0000, Claudiu.Beznea@...rochip.com wrote:
>>> On 23.06.2021 17:19, Alan Stern wrote:
>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>
>>>> On Wed, Jun 23, 2021 at 02:09:16PM +0000, Claudiu.Beznea@...rochip.com wrote:
>>>>> On 23.06.2021 16:59, Alan Stern wrote:
>>>>>> One thing you might consider changing: The name of the
>>>>>> ohci_at91_port_suspend routine is misleading.  It doesn't really
>>>>>> handle suspending the port; instead it handles the clocks that drive
>>>>>> the entire OHCI controller.  Right?
>>>>>
>>>>> It does both as far as I can tell at the moment.
>>>>
>>>> But the name suggests that it only handles suspending a port.  That's
>>>> misleading.
>>>>
>>>> And the way it is used in the SetPortFeature(USB_PORT_FEAT_SUSPEND)
>>>> case in ohci_at91_hub_control is just plain wrong.  It won't merely
>>>> suspend a single port; it will disable the entire OHCI controller.
>>>
>>> Agree with all the above!
>>
>> Are there any systems beside the SAMA7G5 and others you tested which
>> might be affected by this patch?  Do they all work pretty much the
>> same way?  (I want to make sure no others will be adversely affected
>> by this change.)
> 
> I tested it on SAMA7G5, SAMA5D2 and SAM9X60. I tested the suspend/resume
> to/from mem. 

To be sure it has been correctly understood: after suspend/resume cycle I
did USB tests like checking the USB device is recognized, writing data to a
USB mass storage device.

> On SAMA5D2 and SAM9X60 there is no clock provided by
> transceiver A to OHCI. I encountered no issues on tested systems. These IPs
> are also present on SAMA5D3 and SAMA5D4 systems which I haven't tested as I
> expect to behave as SAMA5D2 (as the clocking scheme is the same with
> SAMA5D2). I can also try it on a SAMA5D3 (I don't have a SAMA5D4 with me at
> the moment), tough, just to be sure nothing is broken there too.
> 
> Thank you,
> Claudiu Beznea
> 
>>
>> Alan Stern
>>
>