Re: [PATCH] PCI: Add PCI_EXT_CAP_ID_PL_64GT define

[412574090]

> On Tue, Aug 06, 2024 at 10:27:46AM +0800, 412574090@xxxxxxx wrote:
> > From: weiyufeng <weiyufeng@xxxxxxxxxx>
> > 
> > PCIe r6.0, sec 7.7.7.1, defines a new 64.0 GT/s PCIe Extended Capability
> > ID,Add the define for PCI_EXT_CAP_ID_PL_64GT for drivers that will want
> > this whilst doing Gen6 accesses.
> > 
> > Signed-off-by: weiyufeng <weiyufeng@xxxxxxxxxx>
> > ---
> >  include/uapi/linux/pci_regs.h | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> > index 94c00996e633..cc875534dae1 100644
> > --- a/include/uapi/linux/pci_regs.h
> > +++ b/include/uapi/linux/pci_regs.h
> > @@ -741,6 +741,7 @@
> >  #define PCI_EXT_CAP_ID_DLF	0x25	/* Data Link Feature */
> >  #define PCI_EXT_CAP_ID_PL_16GT	0x26	/* Physical Layer 16.0 GT/s */
> >  #define PCI_EXT_CAP_ID_PL_32GT  0x2A    /* Physical Layer 32.0 GT/s */
> > +#define PCI_EXT_CAP_ID_PL_64GT  0x31    /* Physical Layer 64.0 GT/s */
>
> It probably makes sense to add this (with the corrections noted by
> Ilpo), but I *would* like to see where it's used.
>
> I asked a similar question at
> https://lore.kernel.org/all/20230531095713.293229-1-ben.dooks@xxxxxxxxxxxxxxx/
> when we added PCI_EXT_CAP_ID_PL_32GT, but never got a specific
> response.  I don't really want to end up with drivers doing their own
> thing if it's something that could be done in the PCI core and shared.
>
PCI_EXT_CAP_ID_PL_32GT and PCI_EXT_CAP_ID_PL_64GT have not used now,but 
PCI_EXT_CAP_ID_PL_16GT have usage example,in drivers/pci/controller/dwc/pcie-tegra194.c
function config_gen3_gen4_eq_presets():

offset = dw_pcie_find_ext_capability(pci,
				     PCI_EXT_CAP_ID_PL_16GT) +
		PCI_PL_16GT_LE_CTRL;

PCI_EXT_CAP_ID_PL_32GT and PCI_EXT_CAP_ID_PL_64GT could be used while need to
get this similar attribute。

> >  #define PCI_EXT_CAP_ID_DOE	0x2E	/* Data Object Exchange */
> >  #define PCI_EXT_CAP_ID_MAX	PCI_EXT_CAP_ID_DOE
> >  
> > -- 
> > 2.25.1
> > 
--
Thanks,

weiyufeng