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

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Message-ID: <6a33e55d-b101-cda2-7f53-ce6e5e6ace93@microchip.com>
Date:   Thu, 1 Jul 2021 05:45:50 +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 30.06.2021 21:21, Alan Stern wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On Wed, Jun 30, 2021 at 02:46:47PM +0000, Claudiu.Beznea@...rochip.com wrote:
>> On 24.06.2021 16:23, Alan Stern wrote:
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>
>>> On Thu, Jun 24, 2021 at 06:40:25AM +0000, Claudiu.Beznea@...rochip.com wrote:
>>>> On 23.06.2021 19:41, Alan Stern wrote:
>>>>> 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. 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.
>>>
>>> That doesn't answer my question.  I asked if there were any systems
>>> which might be affected by your patch, and you listed a bunch of
>>> systems that _aren't_ affected (that is, they continue to work
>>> properly).
>>
>> I wrongly understood the initial question.
>>
>>>
>>> What systems might run into trouble with this patch?
>>
>> These are all I haven't tested and might be affected:
>> AT91RM9200,
>> SAM9260,
>> SAM9261,
>> SAM9263,
>> SAM9N12,
>> SAM9X35,
>> SAM9G45.
>>
>> The last two (SAM9X35 and SAM9G45) have the same clocking scheme with
>> SAMA5D2 (which I tested). For the rest of them I cannot find the clocking
>> scheme in datasheet and don't have them to test (at least at the moment).
> 
> I see.  That seems reasonable; the others are probably the same as the
> ones you tested.
> 
> Did you ever answer the question that Nicolas raised back on June 9 in:
> 
>         https://marc.info/?l=linux-usb&m=162324242003349&w=2

Not directly. I replied previously in this thread "For run-time control
(via ohci_at91_hub_control()), I agree with you that
the current implemented approach is not healthy (taking into account the
clock scheme above) and the fact that we do force the ports suspend on
ohci_at91_hub_control()". Nicolas was referring to ohci_at91_port_suspend()
calls in ohci_at91_hub_control() so I agreed with him that work might need
to be done also for this function.

Thank you,
Claudiu Beznea


> 
> Alan Stern
>