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Subject[PATCH v2 10/27] pci: Add pci_mmap_resource_range() and use it for ARM64
Date
From: David Woodhouse <dwmw@amazon.co.uk>

Starting to leave behind the legacy of the pci_mmap_page_range()
interface which takes "user-visible" BAR addresses. This takes just the
resource and offset.

For now, both APIs coexist and depending on the platform, one is
implemented as a wrapper around the other.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
Documentation/filesystems/sysfs-pci.txt | 10 ++--
arch/arm64/include/asm/pci.h | 2 +
drivers/pci/Makefile | 2 +-
drivers/pci/mmap.c | 84 +++++++++++++++++++++++++++++++++
drivers/pci/pci-sysfs.c | 13 ++---
drivers/pci/pci.h | 4 +-
include/linux/pci.h | 19 ++++++--
7 files changed, 114 insertions(+), 20 deletions(-)
create mode 100644 drivers/pci/mmap.c

diff --git a/Documentation/filesystems/sysfs-pci.txt b/Documentation/filesystems/sysfs-pci.txt
index 46b95d8..06f1d64 100644
--- a/Documentation/filesystems/sysfs-pci.txt
+++ b/Documentation/filesystems/sysfs-pci.txt
@@ -113,9 +113,13 @@ Supporting PCI access on new platforms
--------------------------------------

In order to support PCI resource mapping as described above, Linux platform
-code must define HAVE_PCI_MMAP and provide a pci_mmap_page_range function.
-Platforms are free to only support subsets of the mmap functionality, but
-useful return codes should be provided.
+code should ideally define ARCH_GENERIC_PCI_MMAP_RESOURCE and use the generic
+implementation of that functionality. To support the historical interface of
+mmap() through files in /proc/bus/pci, platforms may also set HAVE_PCI_MMAP.
+
+Alternatively, platforms which set HAVE_PCI_MMAP may provide their own
+implementation of pci_mmap_page_range() instead of defining
+ARCH_GENERIC_PCI_MMAP_RESOURCE.

Platforms which support write-combining maps of PCI resources must define
arch_can_pci_mmap_wc() which shall evaluate to non-zero at runtime when
diff --git a/arch/arm64/include/asm/pci.h b/arch/arm64/include/asm/pci.h
index b9a7ba9..1fc1974 100644
--- a/arch/arm64/include/asm/pci.h
+++ b/arch/arm64/include/asm/pci.h
@@ -22,6 +22,8 @@
*/
#define PCI_DMA_BUS_IS_PHYS (0)

+#define ARCH_GENERIC_PCI_MMAP_RESOURCE 1
+
extern int isa_dma_bridge_buggy;

#ifdef CONFIG_PCI
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index 8db5079..3d40e41 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -4,7 +4,7 @@

obj-y += access.o bus.o probe.o host-bridge.o remove.o pci.o \
pci-driver.o search.o pci-sysfs.o rom.o setup-res.o \
- irq.o vpd.o setup-bus.o vc.o
+ irq.o vpd.o setup-bus.o vc.o mmap.o
obj-$(CONFIG_PROC_FS) += proc.o
obj-$(CONFIG_SYSFS) += slot.o

diff --git a/drivers/pci/mmap.c b/drivers/pci/mmap.c
new file mode 100644
index 0000000..9ba720b
--- /dev/null
+++ b/drivers/pci/mmap.c
@@ -0,0 +1,84 @@
+/*
+ * mmap.c — generic PCI resource mmap helper
+ *
+ * Copyright © 2017 Amazon.com, Inc. or its affiliates.
+ *
+ * Author: David Woodhouse <dwmw2@infradead.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+
+ */
+
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/pci.h>
+
+#ifdef ARCH_GENERIC_PCI_MMAP_RESOURCE
+/* Modern setup: generic pci_mmap_resource_range(), and implement the legacy
+ * pci_mmap_page_range() (if needed) as a wrapper round it. */
+
+#ifdef HAVE_PCI_MMAP
+int pci_mmap_page_range(struct pci_dev *pdev, int bar,
+ struct vm_area_struct *vma,
+ enum pci_mmap_state mmap_state, int write_combine)
+{
+ /* Adjust vm_pgoff to be the offset within the resource */
+ resource_size_t start, end;
+
+ pci_resource_to_user(pdev, bar, &pdev->resource[bar], &start, &end);
+ vma->vm_pgoff -= start >> PAGE_SHIFT;
+ return pci_mmap_resource_range(pdev, bar, vma, mmap_state, write_combine);
+}
+#endif
+
+static const struct vm_operations_struct pci_phys_vm_ops = {
+#ifdef CONFIG_HAVE_IOREMAP_PROT
+ .access = generic_access_phys,
+#endif
+};
+
+int pci_mmap_resource_range(struct pci_dev *pdev, int bar,
+ struct vm_area_struct *vma,
+ enum pci_mmap_state mmap_state, int write_combine)
+{
+ unsigned long size;
+
+ if (mmap_state == pci_mmap_io)
+ return -EINVAL;
+
+ size = ((pci_resource_len(pdev, bar) - 1) >> PAGE_SHIFT) + 1;
+ if (vma->vm_pgoff + vma_pages(vma) > size)
+ return -EINVAL;
+
+ if (write_combine)
+ vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+ else
+ vma->vm_page_prot = pgprot_device(vma->vm_page_prot);
+
+ vma->vm_pgoff += (pci_resource_start(pdev, bar) >> PAGE_SHIFT);
+ vma->vm_ops = &pci_phys_vm_ops;
+
+ return io_remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
+ vma->vm_end - vma->vm_start, vma->vm_page_prot);
+}
+
+#elif defined(HAVE_PCI_MMAP) /* && !ARCH_GENERIC_PCI_MMAP_RESOURCE */
+/* Legacy setup: Impement pci_mmap_resource_range() as a wrapper around
+ the architecture's pci_mmap_page_range(), converting to "user visible"
+ addresses as necessary. */
+int pci_mmap_resource_range(struct pci_dev *pdev, int bar,
+ struct vm_area_struct *vma,
+ enum pci_mmap_state mmap_state, int write_combine)
+{
+ resource_size_t start, end;
+ /* pci_mmap_page_range() expects the same kind of entry as coming
+ * from /proc/bus/pci/ which is a "user visible" value. If this is
+ * different from the resource itself, arch will do necessary fixup.
+ */
+ pci_resource_to_user(pdev, bar, &pdev->resource[bar], &start, &end);
+ vma->vm_pgoff += start >> PAGE_SHIFT;
+ return pci_mmap_page_range(pdev, bar, vma, mmap_state, write_combine);
+}
+#endif
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index bfd9efe..10feb98 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -980,7 +980,7 @@ void pci_remove_legacy_files(struct pci_bus *b)
}
#endif /* HAVE_PCI_LEGACY */

-#ifdef HAVE_PCI_MMAP
+#if defined(HAVE_PCI_MMAP) || defined(ARCH_GENERIC_PCI_MMAP_RESOURCE)

int pci_mmap_fits(struct pci_dev *pdev, int resno, struct vm_area_struct *vma,
enum pci_mmap_api mmap_api)
@@ -1019,7 +1019,6 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
int bar = (unsigned long)attr->private;
enum pci_mmap_state mmap_type;
- resource_size_t start, end;
struct resource *res = &pdev->resource[bar];

if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
@@ -1033,15 +1032,9 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
(u64)pci_resource_len(pdev, bar));
return -EINVAL;
}
-
- /* pci_mmap_page_range() expects the same kind of entry as coming
- * from /proc/bus/pci/ which is a "user visible" value. If this is
- * different from the resource itself, arch will do necessary fixup.
- */
- pci_resource_to_user(pdev, bar, res, &start, &end);
- vma->vm_pgoff += start >> PAGE_SHIFT;
mmap_type = res->flags & IORESOURCE_MEM ? pci_mmap_mem : pci_mmap_io;
- return pci_mmap_page_range(pdev, bar, vma, mmap_type, write_combine);
+
+ return pci_mmap_resource_range(pdev, bar, vma, mmap_type, write_combine);
}

static int pci_mmap_resource_uc(struct file *filp, struct kobject *kobj,
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 8dd38e6..8e5ca2d 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -21,14 +21,14 @@ void pci_create_firmware_label_files(struct pci_dev *pdev);
void pci_remove_firmware_label_files(struct pci_dev *pdev);
#endif
void pci_cleanup_rom(struct pci_dev *dev);
-#ifdef HAVE_PCI_MMAP
+
enum pci_mmap_api {
PCI_MMAP_SYSFS, /* mmap on /sys/bus/pci/devices/<BDF>/resource<N> */
PCI_MMAP_PROCFS /* mmap on /proc/bus/pci/<BDF> */
};
int pci_mmap_fits(struct pci_dev *pdev, int resno, struct vm_area_struct *vmai,
enum pci_mmap_api mmap_api);
-#endif
+
int pci_probe_reset_function(struct pci_dev *dev);

/**
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 7173a67..ff1c818 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1626,10 +1626,21 @@ static inline int pci_get_new_domain_nr(void) { return -ENOSYS; }

#include <asm/pci.h>

-/* Map a range of PCI memory or I/O space for a device into user space.
- * Architectures provide this function if they set HAVE_PCI_MMAP, and
- * it accepts the 'write_combine' argument when arch_can_pci_mmap_wc()
- * evaluates to nonzero. */
+/* These two functions provide almost identical functionality. Depennding
+ * on the architecture, one will be implemented as a wrapper aroudn the
+ * other (in drivers/pci/mmap.c).
+ *
+ * pci_mmap_resource_range() maps a specific BAR, and vm->vm_pgoff
+ * is expected to be an offset within that region.
+ *
+ * pci_mmap_page_range() is the legacy architecture-specific interface,
+ * which accepts a "user visible" resource address converted by
+ * pci_resource_to_user(), as used in the legacy mmap() interface in
+ * /proc/bus/pci/.
+ */
+int pci_mmap_resource_range(struct pci_dev *dev, int bar,
+ struct vm_area_struct *vma,
+ enum pci_mmap_state mmap_state, int write_combine);
int pci_mmap_page_range(struct pci_dev *pdev, int bar,
struct vm_area_struct *vma,
enum pci_mmap_state mmap_state, int write_combine);
--
2.9.3
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