Re: [PATCH v2] Extending kernel option pci=resource_alignment to be able to specify PCI device/vendor IDs

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Jun 22, 2016 at 06:33:48AM +0000, Koehrer Mathias (ETAS/ESW5) wrote:
> Some uio based PCI drivers (e.g. uio_cif) do not work if the assigned 
> PCI memory resources are not page aligned.
> By using the kernel option "pci=resource_alignment" it is possible to force
> single PCI boards to use page alignment for their memory resources.
> However, this is fairly cumbersome if multiple of these boards are in use as 
> the specification of the cards has to be done via PCI bus/slot/function number
> which might change e.g. by adding another board.
> This patch extends the kernel option "pci=resource_alignment" to allow to
> specify the relevant boards via PCI device/vendor (and subdevice/subvendor) ids.
> The specification of the devices via device/vendor is indicated by a leading
> string "pci:" as argument to "pci=resource_alignment".
> The format of the specification is
>   pci:<vendor>:<device>[:<subvendor>:<subdevice>]
> 
> Examples: 
>   pci=resource_alignment=4096@pci:1234:abcd:1234:bcde
>   pci=resource_alignment=pci:1234:abcd
> 
> Signed-off-by: Mathias Koehrer <mathias.koehrer@etas.com>

Thanks, Mathias; I applied this to for-linus for v4.8.

> ---
>  Documentation/kernel-parameters.txt |    2 +
>  drivers/pci/pci.c                   |   66 +++++++++++++++++++++++++-----------
>  2 files changed, 49 insertions(+), 19 deletions(-)
> 
> Index: linux-4.7-rc1/Documentation/kernel-parameters.txt
> ===================================================================
> --- linux-4.7-rc1.orig/Documentation/kernel-parameters.txt
> +++ linux-4.7-rc1/Documentation/kernel-parameters.txt
> @@ -2998,12 +2998,17 @@ bytes respectively. Such letter suffixes
>  		resource_alignment=
>  				Format:
>  				[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
> +				[<order of align>@]pci:<vendor>:<device>\
> +						[:<subvendor>:<subdevice>][; ...]
>  				Specifies alignment and device to reassign
>  				aligned memory resources.
>  				If <order of align> is not specified,
>  				PAGE_SIZE is used as alignment.
>  				PCI-PCI bridge can be specified, if resource
>  				windows need to be expanded.
> +				To specify the alignment for certain types of devices, the
> +				PCI vendor/device (and subvendor/subdevice) may be
> +				specified. E.g. 4096@pci:1234:abcd:1234:bcde
>  		ecrc=		Enable/disable PCIe ECRC (transaction layer
>  				end-to-end CRC checking).
>  				bios: Use BIOS/firmware settings. This is the
> Index: linux-4.7-rc1/drivers/pci/pci.c
> ===================================================================
> --- linux-4.7-rc1.orig/drivers/pci/pci.c
> +++ linux-4.7-rc1/drivers/pci/pci.c
> @@ -4755,6 +4755,7 @@ static DEFINE_SPINLOCK(resource_alignmen
>  static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
>  {
>  	int seg, bus, slot, func, align_order, count;
> +	unsigned short vendor, device, subsystem_vendor, subsystem_device;
>  	resource_size_t align = 0;
>  	char *p;
>  
> @@ -4768,28 +4769,55 @@ static resource_size_t pci_specified_res
>  		} else {
>  			align_order = -1;
>  		}
> -		if (sscanf(p, "%x:%x:%x.%x%n",
> -			&seg, &bus, &slot, &func, &count) != 4) {
> -			seg = 0;
> -			if (sscanf(p, "%x:%x.%x%n",
> -					&bus, &slot, &func, &count) != 3) {
> -				/* Invalid format */
> -				printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: %s\n",
> -					p);
> +		if (strncmp(p, "pci:", 4) == 0) {
> +			/* PCI vendor/device (subvendor/subdevice) ids are specified */
> +			p += 4;
> +			if (sscanf(p, "%hx:%hx:%hx:%hx%n",
> +				&vendor, &device, &subsystem_vendor, &subsystem_device, &count) != 4) {
> +				if (sscanf(p, "%hx:%hx%n", &vendor, &device, &count) != 2) {
> +					printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: pci:%s\n",
> +						p);
> +					break;
> +				}
> +				subsystem_vendor = subsystem_device = 0;
> +			}
> +			p += count;
> +			if ((!vendor || (vendor == dev->vendor)) &&
> +				(!device || (device == dev->device)) &&
> +				(!subsystem_vendor || (subsystem_vendor == dev->subsystem_vendor)) &&
> +				(!subsystem_device || (subsystem_device == dev->subsystem_device))) {
> +				if (align_order == -1)
> +					align = PAGE_SIZE;
> +				else
> +					align = 1 << align_order;
> +				/* Found */
>  				break;
>  			}
>  		}
> -		p += count;
> -		if (seg == pci_domain_nr(dev->bus) &&
> -			bus == dev->bus->number &&
> -			slot == PCI_SLOT(dev->devfn) &&
> -			func == PCI_FUNC(dev->devfn)) {
> -			if (align_order == -1)
> -				align = PAGE_SIZE;
> -			else
> -				align = 1 << align_order;
> -			/* Found */
> -			break;
> +		else {
> +			if (sscanf(p, "%x:%x:%x.%x%n",
> +				&seg, &bus, &slot, &func, &count) != 4) {
> +				seg = 0;
> +				if (sscanf(p, "%x:%x.%x%n",
> +						&bus, &slot, &func, &count) != 3) {
> +					/* Invalid format */
> +					printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: %s\n",
> +						p);
> +					break;
> +				}
> +			}
> +			p += count;
> +			if (seg == pci_domain_nr(dev->bus) &&
> +				bus == dev->bus->number &&
> +				slot == PCI_SLOT(dev->devfn) &&
> +				func == PCI_FUNC(dev->devfn)) {
> +				if (align_order == -1)
> +					align = PAGE_SIZE;
> +				else
> +					align = 1 << align_order;
> +				/* Found */
> +				break;
> +			}
>  		}
>  		if (*p != ';' && *p != ',') {
>  			/* End of param or invalid format */