linux-kernel - Re: [PATCH v2 08/27] ocxl: Save the device serial number in ocxl

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Date:   Mon, 3 Feb 2020 12:53:46 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Alastair D'Silva <alastair@....ibm.com>
CC:     <alastair@...ilva.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        "Vishal Verma" <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Keith Busch" <keith.busch@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Rob Herring" <robh@...nel.org>,
        Anton Blanchard <anton@...abs.org>,
        "Krzysztof Kozlowski" <krzk@...nel.org>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        "Cédric Le Goater" <clg@...d.org>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        "Hari Bathini" <hbathini@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Greg Kurz" <groug@...d.org>, Nicholas Piggin <npiggin@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        <linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
        <linux-nvdimm@...ts.01.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH v2 08/27] ocxl: Save the device serial number in ocxl_fn

On Tue, 3 Dec 2019 14:46:36 +1100
Alastair D'Silva <alastair@....ibm.com> wrote:

> From: Alastair D'Silva <alastair@...ilva.org>
> 
> This patch retrieves the serial number of the card and makes it available
> to consumers of the ocxl driver via the ocxl_fn struct.
> 
> Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
> Acked-by: Frederic Barrat <fbarrat@...ux.ibm.com>
> Acked-by: Andrew Donnellan <ajd@...ux.ibm.com>
> ---
>  drivers/misc/ocxl/config.c | 46 ++++++++++++++++++++++++++++++++++++++
>  include/misc/ocxl.h        |  1 +
>  2 files changed, 47 insertions(+)
> 
> diff --git a/drivers/misc/ocxl/config.c b/drivers/misc/ocxl/config.c
> index fb0c3b6f8312..a9203c309365 100644
> --- a/drivers/misc/ocxl/config.c
> +++ b/drivers/misc/ocxl/config.c
> @@ -71,6 +71,51 @@ static int find_dvsec_afu_ctrl(struct pci_dev *dev, u8 afu_idx)
>  	return 0;
>  }
>  
> +/**

Make sure anything you mark as kernel doc with /** is valid
kernel-doc.

> + * Find a related PCI device (function 0)
> + * @device: PCI device to match
> + *
> + * Returns a pointer to the related device, or null if not found
> + */
> +static struct pci_dev *get_function_0(struct pci_dev *dev)
> +{
> +	unsigned int devfn = PCI_DEVFN(PCI_SLOT(dev->devfn), 0); // Look for function 0

Not sure the trailing comment adds much.

I'd personally not bother with this wrapper at all and just call
the pci functions directly where needed.

> +
> +	return pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus),
> +					dev->bus->number, devfn);
> +}
> +
> +static void read_serial(struct pci_dev *dev, struct ocxl_fn_config *fn)
> +{
> +	u32 low, high;
> +	int pos;
> +
> +	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DSN);
> +	if (pos) {
> +		pci_read_config_dword(dev, pos + 0x04, &low);
> +		pci_read_config_dword(dev, pos + 0x08, &high);
> +
> +		fn->serial = low | ((u64)high) << 32;
> +
> +		return;
> +	}
> +
> +	if (PCI_FUNC(dev->devfn) != 0) {
> +		struct pci_dev *related = get_function_0(dev);
> +
> +		if (!related) {
> +			fn->serial = 0;
> +			return;
> +		}
> +
> +		read_serial(related, fn);
> +		pci_dev_put(related);
> +		return;
> +	}
> +
> +	fn->serial = 0;
> +}
> +
>  static void read_pasid(struct pci_dev *dev, struct ocxl_fn_config *fn)
>  {
>  	u16 val;
> @@ -208,6 +253,7 @@ int ocxl_config_read_function(struct pci_dev *dev, struct ocxl_fn_config *fn)
>  	int rc;
>  
>  	read_pasid(dev, fn);
> +	read_serial(dev, fn);
>  
>  	rc = read_dvsec_tl(dev, fn);
>  	if (rc) {
> diff --git a/include/misc/ocxl.h b/include/misc/ocxl.h
> index 6f7c02f0d5e3..9843051c3c5b 100644
> --- a/include/misc/ocxl.h
> +++ b/include/misc/ocxl.h
> @@ -46,6 +46,7 @@ struct ocxl_fn_config {
>  	int dvsec_afu_info_pos; /* offset of the AFU information DVSEC */
>  	s8 max_pasid_log;
>  	s8 max_afu_index;
> +	u64 serial;
>  };
>  
>  enum ocxl_endian {