From 614ffa927eb7acb1c1fb31f5186f5e3d4b1bca74 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sun, 2 Jun 2024 23:06:29 -0400
Subject: kernel: pci: Add PCI BAR mapping routine

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/dev/pci/pci.c         | 58 +++++++++++++++++++++++++++++++++++++++++++++++
 sys/include/dev/pci/pci.h |  1 +
 2 files changed, 59 insertions(+)

diff --git a/sys/dev/pci/pci.c b/sys/dev/pci/pci.c
index 006b428..3be61d9 100644
--- a/sys/dev/pci/pci.c
+++ b/sys/dev/pci/pci.c
@@ -33,7 +33,9 @@
 #include <sys/panic.h>
 #include <sys/queue.h>
 #include <sys/syslog.h>
+#include <sys/errno.h>
 #include <vm/dynalloc.h>
+#include <machine/bus.h>
 #if defined(__x86_64__)
 #include <machine/io.h>
 #endif
@@ -182,6 +184,62 @@ pci_scan_bus(uint8_t bus)
     }
 }
 
+/*
+ * Convert a BAR number to BAR register offset.
+ *
+ * @dev: Device of BAR to check.
+ * @bar: Bar number.
+ */
+static uint8_t
+pci_get_barreg(struct pci_device *dev, uint8_t bar)
+{
+    switch (bar) {
+    case 0: return PCIREG_BAR0;
+    case 1: return PCIREG_BAR1;
+    case 2: return PCIREG_BAR2;
+    case 3: return PCIREG_BAR3;
+    case 4: return PCIREG_BAR4;
+    case 5: return PCIREG_BAR5;
+    default: return 0;
+    }
+}
+
+/*
+ * Map a PCI(e) BAR into kernel memory.
+ *
+ * @dev: Device of BAR to map.
+ * @bar: BAR number to map.
+ * @vap: Resulting virtual address.
+ */
+int
+pci_map_bar(struct pci_device *dev, uint8_t bar, void **vap)
+{
+    uint8_t bar_reg = pci_get_barreg(dev, bar);
+    uintptr_t tmp;
+    uint32_t size;
+
+    if (bar_reg == 0) {
+        return -EINVAL;
+    }
+
+    /*
+     * Get the length of the region this BAR covers by writing a
+     * mask of 32 bits into the BAR register and seeing how many
+     * bits are unset. We can use this to compute the size of the
+     * region. We know that log2(len) bits must be unset.
+     */
+    tmp = pci_readl(dev, bar_reg);
+    pci_writel(dev, bar_reg, __MASK(32));
+    size = pci_readl(dev, bar_reg);
+    size = ~size + 1;
+
+    /* Now we need to restore the previous value */
+    pci_writel(dev, bar_reg, tmp);
+
+    /* Now do the actual mapping work */
+    return bus_map(dev->bar[bar], size, 0, vap);
+}
+
 /*
  * Read PCI(e) configuration space.
  *
diff --git a/sys/include/dev/pci/pci.h b/sys/include/dev/pci/pci.h
index ad3f7ac..dbbd7ce 100644
--- a/sys/include/dev/pci/pci.h
+++ b/sys/include/dev/pci/pci.h
@@ -77,6 +77,7 @@ int pci_init(void);
 uint32_t pci_readl(struct pci_device *dev, uint32_t offset);
 void pci_writel(struct pci_device *dev, uint32_t offset, uint32_t val);
 void pci_set_cmdreg(struct pci_device *dev, uint16_t bits);
+int pci_map_bar(struct pci_device *dev, uint8_t bar, void **vap);
 struct pci_device *pci_get_device(struct pci_lookup lookup, uint16_t lookup_type);
 
 #endif  /* !_DEV_PCI_H_ */
-- 
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