Messages in this thread | | | Subject | Re: [PATCH V2 2/2] usb: musb: Stop bulk endpoint while queue is rotated | From | Sergei Shtylyov <> | Date | Mon, 23 May 2016 16:40:17 +0300 |
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On 5/23/2016 4:26 PM, Andrew Goodbody wrote:
>>> Ensure that the endpoint is stopped by clearing REQPKT before clearing >>> DATAERR_NAKTIMEOUT before rotating the queue on the dedicated bulk >>> endpoint. >>> This addresses an issue where a race could result in the endpoint >>> receiving data before it was reprogrammed resulting in a warning about >>> such data from musb_rx_reinit before it was thrown away. >>> The data thrown away was a valid packet that had been correctly ACKed >>> which meant the host and device got out of sync. >>> >>> Signed-off-by: Andrew Goodbody <andrew.goodbody@cambrionix.com> >>> Cc: stable@vger.kernel.org >>> --- >>> V2 added comment about clearing REQPKT before DATAERR_NAKTIMEOUT >>> >>> drivers/usb/musb/musb_host.c | 6 ++++++ >>> 1 file changed, 6 insertions(+) >>> >>> diff --git a/drivers/usb/musb/musb_host.c >>> b/drivers/usb/musb/musb_host.c index 2966596..676cb98 100644 >>> --- a/drivers/usb/musb/musb_host.c >>> +++ b/drivers/usb/musb/musb_host.c >>> @@ -997,6 +997,12 @@ static void musb_bulk_nak_timeout(struct musb >> *musb, struct musb_hw_ep *ep, >>> /* clear nak timeout bit */ >>> rx_csr = musb_readw(epio, MUSB_RXCSR); >>> rx_csr |= MUSB_RXCSR_H_WZC_BITS; >>> + /* >>> + * Need to stop the transaction by clearing REQPKT before >> >> Transcation? Maybe transfer? > > The quote from the TRM is "If the DATAERR_NAKTIMEOUT bit is set, the controller can be directed either to continue trying this transaction (until it times out again) by clearing the DATAERR_NAKTIMEOUT bit or to abort the transaction by clearing REQPKT bit before clearing the DATAERR_NAKTIMEOUT bit." > So 'transaction' is correct.
OK.
>>> + * DATAERR_NAKTIMEOUT ref TRM section 16.3.8.2.2.1.2 >> >> Which TRM? Do you understand that the MUSB core is used by multiple >> SoCs? >> I'd recommend referring just to the "abstract" manual or the MUSB >> programmer's guide (section 9.2.2 if you want an exact ref.).
> That would be the AM335x Sitara Processors TRM. I don't have the MUSB programmer's guide, is it available online somewhere?
AFAIK, no.
> I do not understand what you mean by the "abstract" manual.
Just saying "the manual" or "the manuals".
> Would you be OK with "ref MUSB Programmer's Guide section 9.2.2"
Yes. However, that spec calls the bit just "NAK Timeout" in this context, not DATAERR_NAKTIMEOUT. Overall, this spec. uses CamelCase for the register bit names (I recall dbrownell complaining over that and uppercase all the bit names in my patches :-).
> Andrew > >> [...]
MBR, Sergei
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