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

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Hi Bjorn,

> From: Bjorn Helgaas, Sent: Wednesday, September 21, 2022 11:22 AM
> 
> On Wed, Sep 21, 2022 at 12:05:26AM +0000, Yoshihiro Shimoda wrote:
> > Hi Bjorn,
> > > 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 understood it.

> > I'll drop PCI_EXP_LNKCAP_MLW_X32 on v6 patch.
> 
> When you do, add my:
> 
> Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

Thank you! I'll submit v6 patches tomorrow (or later).

Best regards,
Yoshihiro Shimoda





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