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>

2 files changed, 109 insertions, 0 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 */