PCI: Add resizable BAR infrastructure

Add resizable BAR infrastructure, including defines and helper functions to
read the possible sizes of a BAR and update its size.  See PCIe r3.1, sec
7.22.

Link: https://pcisig.com/sites/default/files/specification_documents/ECN_Resizable-BAR_24Apr2008.pdf
Signed-off-by: Christian König <christian.koenig@amd.com>
[bhelgaas: rename to functions with "rebar" (to match #defines), drop shift
#defines, drop "_MASK" suffixes, fix typos, fix kerneldoc]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

3 files changed, 115 insertions, 2 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6078dfc11b11..832b96756e83 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2966,6 +2966,107 @@ bool pci_acs_path_enabled(struct pci_dev *start,
 }
 
 /**
+ * pci_rebar_find_pos - find position of resize ctrl reg for BAR
+ * @pdev: PCI device
+ * @bar: BAR to find
+ *
+ * Helper to find the position of the ctrl register for a BAR.
+ * Returns -ENOTSUPP if resizable BARs are not supported at all.
+ * Returns -ENOENT if no ctrl register for the BAR could be found.
+ */
+static int pci_rebar_find_pos(struct pci_dev *pdev, int bar)
+{
+        unsigned int pos, nbars, i;
+        u32 ctrl;
+
+        pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
+        if (!pos)
+                return -ENOTSUPP;
+
+        pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
+        nbars = (ctrl & PCI_REBAR_CTRL_NBAR_MASK) >>
+                    PCI_REBAR_CTRL_NBAR_SHIFT;
+
+        for (i = 0; i < nbars; i++, pos += 8) {
+                int bar_idx;
+
+                pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
+                bar_idx = ctrl & PCI_REBAR_CTRL_BAR_IDX;
+                if (bar_idx == bar)
+                        return pos;
+        }
+
+        return -ENOENT;
+}
+
+/**
+ * pci_rebar_get_possible_sizes - get possible sizes for BAR
+ * @pdev: PCI device
+ * @bar: BAR to query
+ *
+ * Get the possible sizes of a resizable BAR as bitmask defined in the spec
+ * (bit 0=1MB, bit 19=512GB). Returns 0 if BAR isn't resizable.
+ */
+u32 pci_rebar_get_possible_sizes(struct pci_dev *pdev, int bar)
+{
+        int pos;
+        u32 cap;
+
+        pos = pci_rebar_find_pos(pdev, bar);
+        if (pos < 0)
+                return 0;
+
+        pci_read_config_dword(pdev, pos + PCI_REBAR_CAP, &cap);
+        return (cap & PCI_REBAR_CAP_SIZES) >> 4;
+}
+
+/**
+ * pci_rebar_get_current_size - get the current size of a BAR
+ * @pdev: PCI device
+ * @bar: BAR to set size to
+ *
+ * Read the size of a BAR from the resizable BAR config.
+ * Returns size if found or negative error code.
+ */
+int pci_rebar_get_current_size(struct pci_dev *pdev, int bar)
+{
+        int pos;
+        u32 ctrl;
+
+        pos = pci_rebar_find_pos(pdev, bar);
+        if (pos < 0)
+                return pos;
+
+        pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
+        return (ctrl & PCI_REBAR_CTRL_BAR_SIZE) >> 8;
+}
+
+/**
+ * pci_rebar_set_size - set a new size for a BAR
+ * @pdev: PCI device
+ * @bar: BAR to set size to
+ * @size: new size as defined in the spec (0=1MB, 19=512GB)
+ *
+ * Set the new size of a BAR as defined in the spec.
+ * Returns zero if resizing was successful, error code otherwise.
+ */
+int pci_rebar_set_size(struct pci_dev *pdev, int bar, int size)
+{
+        int pos;
+        u32 ctrl;
+
+        pos = pci_rebar_find_pos(pdev, bar);
+        if (pos < 0)
+                return pos;
+
+        pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
+        ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE;
+        ctrl |= size << 8;
+        pci_write_config_dword(pdev, pos + PCI_REBAR_CTRL, ctrl);
+        return 0;
+}
+
+/**
  * pci_swizzle_interrupt_pin - swizzle INTx for device behind bridge
  * @dev: the PCI device
  * @pin: the INTx pin (1=INTA, 2=INTB, 3=INTC, 4=INTD)
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index a6560c9baa52..33469a33738d 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -366,4 +366,12 @@ int acpi_get_rc_resources(struct device *dev, const char *hid, u16 segment,
                           struct resource *res);
 #endif
 
+u32 pci_rebar_get_possible_sizes(struct pci_dev *pdev, int bar);
+int pci_rebar_get_current_size(struct pci_dev *pdev, int bar);
+int pci_rebar_set_size(struct pci_dev *pdev, int bar, int size);
+static inline u64 pci_rebar_size_to_bytes(int size)
+{
+        return 1ULL << (size + 20);
+}
+
 #endif /* DRIVERS_PCI_H */
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index f8d58045926f..d34000a59f24 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -939,9 +939,13 @@
 #define PCI_SATA_SIZEOF_LONG    16
 
 /* Resizable BARs */
+#define PCI_REBAR_CAP           4       /* capability register */
+#define  PCI_REBAR_CAP_SIZES            0x00FFFFF0  /* supported BAR sizes */
 #define PCI_REBAR_CTRL          8       /* control register */
-#define  PCI_REBAR_CTRL_NBAR_MASK       (7 << 5)        /* mask for # bars */
-#define  PCI_REBAR_CTRL_NBAR_SHIFT      5       /* shift for # bars */
+#define  PCI_REBAR_CTRL_BAR_IDX         0x00000007  /* BAR index */
+#define  PCI_REBAR_CTRL_NBAR_MASK       0x000000E0  /* # of resizable BARs */
+#define  PCI_REBAR_CTRL_NBAR_SHIFT      5           /* shift for # of BARs */
+#define  PCI_REBAR_CTRL_BAR_SIZE        0x00001F00  /* BAR size */
 
 /* Dynamic Power Allocation */
 #define PCI_DPA_CAP             4       /* capability register */