Message-ID: <20210701140131.GA772273@rowland.harvard.edu>
Date:   Thu, 1 Jul 2021 10:01:31 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Claudiu.Beznea@...rochip.com
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 Thu, Jul 01, 2021 at 05:45:50AM +0000, Claudiu.Beznea@...rochip.com wrote:
> 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.

All right.  I guess this is the best that can be done at this time.

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

Greg KH may not have the original patch still in his queue.  And in any 
case he'll probably ask you to resubmit it after the current merge 
window ends.

Alan Stern

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