linux-kernel - RE: [PATCH] drivers: usb: fsl: Workaround for USB erratum-A005275

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Message-ID: <SN1PR0301MB1629976DA97C5A81F11EF64BF3770@SN1PR0301MB1629.namprd03.prod.outlook.com>
Date:	Mon, 3 Aug 2015 05:59:44 +0000
From:	Badola Nikhil <nikhil.badola@...escale.com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	Ramneek Mehresh <ramneek.mehresh@...escale.com>
Subject: RE: [PATCH] drivers: usb: fsl: Workaround for USB erratum-A005275

> -----Original Message-----
> From: Alan Stern [mailto:stern@...land.harvard.edu]
> Sent: Friday, July 31, 2015 10:04 PM
> To: Badola Nikhil-B46172
> Cc: linux-kernel@...r.kernel.org; linux-usb@...r.kernel.org;
> gregkh@...uxfoundation.org; Mehresh Ramneek-B31383
> Subject: Re: [PATCH] drivers: usb: fsl: Workaround for USB erratum-A005275
> 
> On Fri, 31 Jul 2015, Nikhil Badola wrote:
> 
> > Incoming packets in high speed are randomly corrupted by h/w resulting
> > in multiple errors. This workaround makes FS as default mode in all
> > affected socs by disabling HS chirp signalling.This errata does not
> > affect FS and LS mode.
> >
> > Forces all HS devices to connect in FS mode for all socs affected by
> > this erratum:
> > P3041 and P2041 rev 1.0 and 1.1
> > P5020 and P5010 rev 1.0 and 2.0
> > P5040, P1010 and T4240 rev 1.0
> 
> Ooh, that's a really bad bug.  People will be pretty annoyed that they can't
> use high speed connections.
> 
> > --- a/drivers/usb/host/ehci-hub.c
> > +++ b/drivers/usb/host/ehci-hub.c
> > @@ -1222,6 +1222,13 @@ int ehci_hub_control(
> >  				ehci->reset_done [wIndex] = jiffies
> >  						+ msecs_to_jiffies (50);
> >  			}
> > +
> > +			/* Force full-speed connect for FSL high-speed
> erratum;
> > +			 * disable HS Chirp by setting PFSC bit
> > +			 */
> > +			if (ehci_has_fsl_hs_errata(ehci))
> > +				temp |= (1 << PORTSC_FSL_PFSC);
> > +
> 
> This hunk was added in the wrong place.  It should come before the closing '}'
> above, not after.  That's because you don't want to force a full-speed
> connection if the device is already using low speed.

I agree that the hunk must be added before '}' i.e. in else block but reason being
our controllers have tt . Please correct me if I am wrong.
However the code executes "else" block in case of high speed as well as low speed device,
and low speed device is working fine in that case (I checked a Dell USB Keyboard).

> 
> > --- a/drivers/usb/host/ehci.h
> > +++ b/drivers/usb/host/ehci.h
> > @@ -215,6 +215,7 @@ struct ehci_hcd {			/* one per
> controller */
> >  	/* SILICON QUIRKS */
> >  	unsigned		no_selective_suspend:1;
> >  	unsigned		has_fsl_port_bug:1; /* FreeScale */
> > +	unsigned		has_fsl_hs_errata:1;	/* Freescale HS quirk
> */
> >  	unsigned		big_endian_mmio:1;
> >  	unsigned		big_endian_desc:1;
> >  	unsigned		big_endian_capbase:1;
> > @@ -675,6 +676,17 @@ ehci_port_speed(struct ehci_hcd *ehci, unsigned
> int portsc)
> >  #define	ehci_port_speed(ehci, portsc)
> 	USB_PORT_STAT_HIGH_SPEED
> >  #endif
> >
> > +#define PORTSC_FSL_PFSC	24	/* Port Force Full-Speed Connect */
> > +
> > +#if defined(CONFIG_PPC_85xx)
> > +/* Some Freescale processors have an erratum (USB A-005275) in which
> > + * incoming packets get corrupted in HS mode  */
> > +#define ehci_has_fsl_hs_errata(e)	((e)->has_fsl_hs_errata)
> > +#else
> > +#define ehci_has_fsl_hs_errata(e)	(0)
> > +#endif
> > +
> >
> > /*--------------------------------------------------------------------
> > -----*/
> 
> I would prefer it if you add your new hunk after this /*-----...---*/ dividing
> line (that is, next to the ehci_has_fsl_portno_bug() code) instead of before
> the dividing line.

Agreed. Will make changes in next version.


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