Re: [PATCH v5 03/12] PCI: Add PCI_EXP_LNKCAP_MLW macros

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On Wed, Sep 21, 2022 at 12:05:26AM +0000, Yoshihiro Shimoda wrote:
> Hi Bjorn,
> 
> Thank you for your review!
> 
> > From: Bjorn Helgaas, Sent: Wednesday, September 21, 2022 5:08 AM
> > 
> > On Mon, Sep 05, 2022 at 04:12:48PM +0900, Yoshihiro Shimoda wrote:
> > > Add macros defining Maximum Link Width bits in Link Capabilities
> > > Register.
> > >
> > > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> > > ---
> > >  include/uapi/linux/pci_regs.h | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > >
> > > diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> > > index 57b8e2ffb1dd..c9f4c452e210 100644
> > > --- a/include/uapi/linux/pci_regs.h
> > > +++ b/include/uapi/linux/pci_regs.h
> > > @@ -538,6 +538,13 @@
> > >  #define  PCI_EXP_LNKCAP_SLS_16_0GB 0x00000004 /* LNKCAP2 SLS Vector bit 3 */
> > >  #define  PCI_EXP_LNKCAP_SLS_32_0GB 0x00000005 /* LNKCAP2 SLS Vector bit 4 */
> > >  #define  PCI_EXP_LNKCAP_SLS_64_0GB 0x00000006 /* LNKCAP2 SLS Vector bit 5 */
> > > +#define  PCI_EXP_LNKCAP_MLW_X1	0x00000010 /* Maximum Link Width x1 */
> > > +#define  PCI_EXP_LNKCAP_MLW_X2	0x00000020 /* Maximum Link Width x2 */
> > > +#define  PCI_EXP_LNKCAP_MLW_X4	0x00000040 /* Maximum Link Width x4 */
> > > +#define  PCI_EXP_LNKCAP_MLW_X8	0x00000080 /* Maximum Link Width x8 */
> > > +#define  PCI_EXP_LNKCAP_MLW_X12	0x000000c0 /* Maximum Link Width x12 */
> > > +#define  PCI_EXP_LNKCAP_MLW_X16	0x00000100 /* Maximum Link Width x16 */
> > > +#define  PCI_EXP_LNKCAP_MLW_X32	0x00000200 /* Maximum Link Width x32 */
> > 
> > In PCIe r6.0, x32 is mentioned a few times, but not actually defined
> > for Link Capabilities.  Has it been defined in an ECN or something?
> 
> I should have looked PCIe r6.0, but I looked PCIe r4.0 v1.0 and it mentioned x32.
> So, I wrote the x32 macro.

Sure enough.  It's there in r4.0 and r5.0, but dropped from r6.0.
Wish there were a git tree where we could see whether this was a
mistake or there was some reason for it.  Maybe nobody had actually
built x32 hardware and they wanted to reserve the flexibility for
something else.

> I'll drop PCI_EXP_LNKCAP_MLW_X32 on v6 patch.

When you do, add my:

Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>




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