linux-kernel - Re: [PATCH kernel 2/4] pci/doe: Support discovery version

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Message-ID: <20240208220027.GA975008@bhelgaas>
Date: Thu, 8 Feb 2024 16:00:27 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Alexey Kardashevskiy <aik@....com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jonathan Cameron <jonathan.cameron@...wei.com>,
	Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH kernel 2/4] pci/doe: Support discovery version

On Thu, Feb 01, 2024 at 05:02:26PM +1100, Alexey Kardashevskiy wrote:
> PCIe spec v6.1 defines a "DOE Discovery Version" field in the DOE Discovery
> Request Data Object Contents (3rd DW) as:

Please include spec section number, e.g., "PCIe r6.1, sec xx.xx".

(Also note PCI-SIG uses "revision" as the major, "version" as the
minor, so this would be "PCIe r6.1", not "PCIe v6.1".)

> 15:8 DOE Discovery Version – must be 02h if the Capability Version in
> the Data Object Exchange Extended Capability is 02h or greater.
> 
> Add support for the version on devices with the DOE v2 capability.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@....com>
> ---
>  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..b9c681f14181 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_DISCOVER_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..f57def002175 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 disver = FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_DISCOVER_VER,
> +				(capver >= 2) ? 2 : 0);
>  	u32 request_pl = FIELD_PREP(PCI_DOE_DATA_OBJECT_DISC_REQ_3_INDEX,
> -				    *index);
> +				    *index) | disver;
>  	__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;
>  
> -- 
> 2.41.0
>