On Mon, 23 Jan 2012, Jayachandran C. wrote: > From: Jayachandran C <jayachandranc@xxxxxxxxxxxxxxxxx> > > The USB driver code usually uses readl() to read the EHCI register > space to support chips which does not allow 8/16 bit access to the > EHCI registers. > > But in the PCI USB quirk code (drivers/usb/host/pci-quirks.c), > readb() is used in one place. Convert this to use readl as well. > > Signed-off-by: Jayachandran C <jayachandranc@xxxxxxxxxxxxxxxxx> > --- > > [ The Netlogic XLP patches I plan to submit is dependent on this, > otherwise we will need to fix this up with a custom Cache error > handler. Let me know if this is not the right approach. - Thanks.] > > drivers/usb/host/pci-quirks.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c > index caf8742..ea7edfe 100644 > --- a/drivers/usb/host/pci-quirks.c > +++ b/drivers/usb/host/pci-quirks.c > @@ -630,7 +630,7 @@ static void __devinit quirk_usb_disable_ehci(struct pci_dev *pdev) > if (base == NULL) > return; > > - cap_length = readb(base); > + cap_length = readl(base) & 0xff; > op_reg_base = base + cap_length; > > /* EHCI 0.96 and later may have "extended capabilities" This is potentially dangerous, because it involves byte-ordering within a word. See the comment in include/linux/usb/ehci_def.h where hc_capbase is defined, and the comment in ehci.h where ehci_big_endian_capbase is defined. Fortunately the only driver that sets the big_endian_capbase flag is ehci-grlib, which isn't PCI. So there shouldn't be any problem. However you might want to mention these issues in the patch description, and maybe even as a comment in the quirk_usb_disable_ehci code. In theory, big-endian PCI controllers all do this the wrong way. That is, since CAPLENGTH is specified as occupying the byte at the lowest address in the word, it should end up as the highest-order byte of a big-endian value. I guess people discovered that if they followed the spec in this regard, their controllers wouldn't work with regular PCI drivers. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
