Re: [PATCH 07/20] PCI: implement Devres interface to map PCI config space

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

Arnd, all,

On Mon, Feb 27, 2017 at 03:14:18PM +0000, Lorenzo Pieralisi wrote:
> The introduction of the pci_remap_cfgspace() interface allows
> PCI host controller drivers to map PCI config space through a
> dedicated kernel interface. Current PCI host controller drivers
> use the devm_ioremap_* Devres interfaces to map PCI configuration
> space regions so in order to update them to the new
> pci_remap_cfgspace() mapping interface a new set of Devres interfaces
> should be implemented so that PCI host controller drivers can make
> use of them.
> 
> Introduce two new functions in the PCI kernel layer and Devres
> documentation:
> 
> - devm_pci_remap_cfgspace()
> - devm_pci_remap_cfg_resource()
> 
> so that PCI host controller drivers can make use of them to map
> PCI configuration space regions.
> 
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> ---
>  Documentation/driver-model/devres.txt |  6 ++-
>  drivers/pci/pci.c                     | 82 +++++++++++++++++++++++++++++++++++
>  include/linux/pci.h                   |  5 +++
>  3 files changed, 91 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
> index bf34d5b..e72587f 100644
> --- a/Documentation/driver-model/devres.txt
> +++ b/Documentation/driver-model/devres.txt
> @@ -342,8 +342,10 @@ PER-CPU MEM
>    devm_free_percpu()
>  
>  PCI
> -  pcim_enable_device()	: after success, all PCI ops become managed
> -  pcim_pin_device()	: keep PCI device enabled after release
> +  devm_pci_remap_cfgspace()	: ioremap PCI configuration space
> +  devm_pci_remap_cfg_resource()	: ioremap PCI configuration space resource
> +  pcim_enable_device()		: after success, all PCI ops become managed
> +  pcim_pin_device()		: keep PCI device enabled after release
>  
>  PHY
>    devm_usb_get_phy()
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index bfb3c6e..1e435c2 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3401,6 +3401,88 @@ void pci_unmap_iospace(struct resource *res)
>  #endif
>  }
>  
> +/**
> + * devm_pci_remap_cfgspace - Managed pci_remap_cfgspace()
> + * @dev: Generic device to remap IO address for
> + * @offset: BUS offset to map
> + * @size: Size of map
> + *
> + * Managed pci_remap_cfgspace().  Map is automatically unmapped on driver
> + * detach.
> + */
> +void __iomem *devm_pci_remap_cfgspace(struct device *dev,
> +				      resource_size_t offset,
> +				      resource_size_t size)
> +{
> +	void __iomem **ptr, *addr;
> +
> +	ptr = devres_alloc(devm_ioremap_release, sizeof(*ptr), GFP_KERNEL);
> +	if (!ptr)
> +		return NULL;
> +
> +	addr = pci_remap_cfgspace(offset, size);

Provided this series is acceptable as-is, I noticed that I have
to add a #define for pci_remap_cfgspace() on all arches that do
not include asm-generic/io.h in their asm/io.h, I missed that,
please shout if you see an easier way to implement a
pci_remap_cfgspace() fall-back to ioremap_nocache() on all arches
that do not override it.

Thanks !
Lorenzo

> +	if (addr) {
> +		*ptr = addr;
> +		devres_add(dev, ptr);
> +	} else
> +		devres_free(ptr);
> +
> +	return addr;
> +}
> +EXPORT_SYMBOL(devm_pci_remap_cfgspace);
> +
> +/**
> + * devm_pci_remap_cfg_resource - check, request region and ioremap cfg resource
> + * @dev: generic device to handle the resource for
> + * @res: configuration space resource to be handled
> + *
> + * Checks that a resource is a valid memory region, requests the memory
> + * region and ioremaps with pci_remap_cfgspace() API that ensures the
> + * proper PCI configuration space memory attributes are guaranteed.
> + *
> + * All operations are managed and will be undone on driver detach.
> + *
> + * Returns a pointer to the remapped memory or an ERR_PTR() encoded error code
> + * on failure. Usage example:
> + *
> + *	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + *	base = devm_pci_remap_cfg_resource(&pdev->dev, res);
> + *	if (IS_ERR(base))
> + *		return PTR_ERR(base);
> + */
> +void __iomem *devm_pci_remap_cfg_resource(struct device *dev,
> +					  struct resource *res)
> +{
> +	resource_size_t size;
> +	const char *name;
> +	void __iomem *dest_ptr;
> +
> +	BUG_ON(!dev);
> +
> +	if (!res || resource_type(res) != IORESOURCE_MEM) {
> +		dev_err(dev, "invalid resource\n");
> +		return IOMEM_ERR_PTR(-EINVAL);
> +	}
> +
> +	size = resource_size(res);
> +	name = res->name ?: dev_name(dev);
> +
> +	if (!devm_request_mem_region(dev, res->start, size, name)) {
> +		dev_err(dev, "can't request region for resource %pR\n", res);
> +		return IOMEM_ERR_PTR(-EBUSY);
> +	}
> +
> +	dest_ptr = devm_pci_remap_cfgspace(dev, res->start, size);
> +	if (!dest_ptr) {
> +		dev_err(dev, "ioremap failed for resource %pR\n", res);
> +		devm_release_mem_region(dev, res->start, size);
> +		dest_ptr = IOMEM_ERR_PTR(-ENOMEM);
> +	}
> +
> +	return dest_ptr;
> +}
> +EXPORT_SYMBOL(devm_pci_remap_cfg_resource);
> +
>  static void __pci_set_master(struct pci_dev *dev, bool enable)
>  {
>  	u16 old_cmd, cmd;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 282ed32..5a3588b 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1199,6 +1199,11 @@ unsigned long pci_address_to_pio(phys_addr_t addr);
>  phys_addr_t pci_pio_to_address(unsigned long pio);
>  int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr);
>  void pci_unmap_iospace(struct resource *res);
> +void __iomem *devm_pci_remap_cfgspace(struct device *dev,
> +				      resource_size_t offset,
> +				      resource_size_t size);
> +void __iomem *devm_pci_remap_cfg_resource(struct device *dev,
> +					  struct resource *res);
>  
>  static inline pci_bus_addr_t pci_bus_address(struct pci_dev *pdev, int bar)
>  {
> -- 
> 2.10.0
>