Re: [PATCH v11 10/10] PCI: Introduce pci_remap_iospace() for remapping PCI I/O bus resources into CPU space
From: Bjorn Helgaas <bhelgaas@google.com>
Date: 2014-09-19 21:54:10
Also in:
linux-arch, linux-arm-kernel, linux-pci, lkml
On Thu, Sep 18, 2014 at 02:30:25AM +0100, Liviu Dudau wrote:
Introduce a default implementation for remapping PCI bus I/O resources onto the CPU address space. Architectures with special needs may provide their own version, but most should be able to use this one.
I see that this is used by Tanmay's APM X-Gene PCIe host controller driver. Since it's not used in this series, it'd be nice to mention where it *will* be used.
quoted hunk ↗ jump to hunk
Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Rob Herring <robh+dt@kernel.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com> --- drivers/pci/pci.c | 33 +++++++++++++++++++++++++++++++++ include/asm-generic/pgtable.h | 4 ++++ include/linux/pci.h | 3 +++ 3 files changed, 40 insertions(+)diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 2c9ac70..654b44c 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c@@ -2704,6 +2704,39 @@ int pci_request_regions_exclusive(struct pci_dev *pdev, const char *res_name) } EXPORT_SYMBOL(pci_request_regions_exclusive); +/** + * pci_remap_iospace - Remap the memory mapped I/O space + * @res: Resource describing the I/O space + * @phys_addr: physical address where the range will be mapped. + * + * Remap the memory mapped I/O space described by the @res + * into the CPU physical address space.
This comment doesn't seem quite right. I think the space is already in the CPU physical address space. ioremap() and friends normally map existing physical space into the *virtual* address space, i.e., they create mappings from a virtual address to a physical address.
Only architectures
+ * that have memory mapped IO defined (and hence PCI_IOBASE)
+ * should call this function.
+ */
+int __weak pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr)
+{
+ int err = -ENODEV;
+
+#ifdef PCI_IOBASE
+ if (!(res->flags & IORESOURCE_IO))
+ return -EINVAL;
+
+ if (res->end > IO_SPACE_LIMIT)
+ return -EINVAL;
+
PCI_IOBASE is a virtual address. So PCI_IOBASE + res->start is also a
virtual address (only for IORESOURCE_IO).
Since res->start is normally a *physical* address, I think it would be less
confusing to do something like this:
vaddr = PCI_IOBASE + res->start;
ioremap_page_range(vaddr, vaddr + resource_size(res), ...);
so we have a hint that the first two ioremap_page_range() parameters are
virtual addresses. It's also confusing that it uses "unsigned long" for
the virtual addresses, when we usually use "void *". But that's out of
scope for this patch.
quoted hunk ↗ jump to hunk
+ err = ioremap_page_range(res->start + (unsigned long)PCI_IOBASE, + res->end + 1 + (unsigned long)PCI_IOBASE, + phys_addr, pgprot_device(PAGE_KERNEL)); +#else + /* this architecture does not have memory mapped I/O space, + so this function should never be called */ + WARN_ON(1); +#endif + + return err; +} + static void __pci_set_master(struct pci_dev *dev, bool enable) { u16 old_cmd, cmd;diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index 53b2acc..977e545 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h@@ -249,6 +249,10 @@ static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b) #define pgprot_writecombine pgprot_noncached #endif +#ifndef pgprot_device +#define pgprot_device pgprot_noncached +#endif + /* * When walking page tables, get the address of the next boundary, * or the end address of the range if that comes earlier. Although nodiff --git a/include/linux/pci.h b/include/linux/pci.h index a494e5d..fc8c529 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h@@ -1100,6 +1100,9 @@ int __must_check pci_bus_alloc_resource(struct pci_bus *bus, resource_size_t), void *alignf_data); + +int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr); + static inline dma_addr_t pci_bus_address(struct pci_dev *pdev, int bar) { struct pci_bus_region region;-- 2.1.0