linux-kernel - Re: [PATCH kernel v3] PCI/DOE: Support discovery version 2

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Message-ID: <CAC41dw9x8H2m=YB66+PA-GwiVkpCyT0PobdWvFXLHpAsQOE0ew@mail.gmail.com>
Date: Wed, 6 Mar 2024 22:22:46 -0800
From: Sathyanarayanan Kuppuswamy Natarajan <sathyanarayanan.nkuppuswamy@...il.com>
To: Alexey Kardashevskiy <aik@....com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Ira Weiny <ira.weiny@...el.com>, 
	Dan Williams <dan.j.williams@...el.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
	Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH kernel v3] PCI/DOE: Support discovery version 2

On Wed, Mar 6, 2024 at 10:09 PM Alexey Kardashevskiy <aik@....com> wrote:
>
>
>
> On 7/3/24 16:06, Kuppuswamy Sathyanarayanan wrote:
> >
> > On 3/6/24 6:20 PM, Alexey Kardashevskiy wrote:
> >> PCIe r6.1, sec 6.30.1.1 defines a "DOE Discovery Version" field in
> >> the DOE Discovery Request Data Object Contents (3rd DW) as:
> >>
> >> 15:8 DOE Discovery Version – must be 02h if the Capability Version in
> >> the Data Object Exchange Extended Capability is 02h or greater.
> >
> > Does this change fix any functional issue? If yes, please add Fixes:
> > tag and probably CC stable?
>
> The issue is that before this patch the DOE driver was following PCIe
> r6.0 and it was not working on a device with DOE cap v2 added in r6.1.
> Is it "fixes"?
>

Since you are enabling support for the newer spec version, I think it will not
fall under bug fix. But it might be qualified for the stable branch.
It depends on
whether you want to support this device in older(stable) kernels.

>
> >>
> >> Add support for the version on devices with the DOE v2 capability.
> >>
> >> Signed-off-by: Alexey Kardashevskiy <aik@....com>
> >> ---
> > Change wise looks fine to me.
> >
> > Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>
> Thanks!
>
> >> Changes:
> >> v3:
> >> * updated subject line
> >> * dropped "DISCOVER_" from the new field macro
> >>
> >> v2:
> >> * added the section number to the commit log
> >> ---
> >>   include/uapi/linux/pci_regs.h |  1 +
> >>   drivers/pci/doe.c             | 11 ++++++++---
> >>   2 files changed, 9 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> >> index a39193213ff2..fbca743b2b86 100644
> >> --- a/include/uapi/linux/pci_regs.h
> >> +++ b/include/uapi/linux/pci_regs.h
> >> @@ -1144,6 +1144,7 @@
> >>   #define PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH                0x0003ffff
> >>
> >>   #define PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX               0x000000ff
> >> +#define PCI_DOE_DATA_OBJECT_DISC_REQ_3_VER          0x0000ff00
> >>   #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_VID         0x0000ffff
> >>   #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL            0x00ff0000
> >>   #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX  0xff000000
> >> diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> >> index 61f0531d2b1d..c94c2b0767f3 100644
> >> --- a/drivers/pci/doe.c
> >> +++ b/drivers/pci/doe.c
> >> @@ -381,11 +381,13 @@ static void pci_doe_task_complete(struct pci_doe_task *task)
> >>      complete(task->private);
> >>   }
> >>
> >> -static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 *index, u16 *vid,
> >> +static int pci_doe_discovery(struct pci_doe_mb *doe_mb, u8 capver, u8 *index, u16 *vid,
> >>                           u8 *protocol)
> >>   {
> >>      u32 request_pl = FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX,
> >> -                                *index);
> >> +                                *index) |
> >> +                     FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_VER,
> >> +                                (capver >= 2) ? 2 : 0);
> >>      __le32 request_pl_le = cpu_to_le32(request_pl);
> >>      __le32 response_pl_le;
> >>      u32 response_pl;
> >> @@ -419,13 +421,16 @@ static int pci_doe_cache_protocols(struct pci_doe_mb *doe_mb)
> >>   {
> >>      u8 index = 0;
> >>      u8 xa_idx = 0;
> >> +    u32 hdr = 0;
> >> +
> >> +    pci_read_config_dword(doe_mb->pdev, doe_mb->cap_offset, &hdr);
> >>
> >>      do {
> >>              int rc;
> >>              u16 vid;
> >>              u8 prot;
> >>
> >> -            rc = pci_doe_discovery(doe_mb, &index, &vid, &prot);
> >> +            rc = pci_doe_discovery(doe_mb, PCI_EXT_CAP_VER(hdr), &index, &vid, &prot);
> >>              if (rc)
> >>                      return rc;
> >>
> >
>
> --
> Alexey
>


-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer