PCI Express support for 2.4 kernel

[Vladimir Kondratiev <vladimir.kondratiev@intel.com>]

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Hi,
PCI-Express platforms will soon appear on the market. It is worth to 
support it.

Following is patch for 2.4.23 kernel. I tested it on my host, it works 
properly.
I did it for i386 only, I have no other architecture to test.

It was patch on the same subject from* Seshadri, Harinarayanan* 
(/harinarayanan.seshadri@intel.com/ 
<mailto:harinarayanan.seshadri@intel.com>) 
http://www.cs.helsinki.fi/linux/linux-kernel/2003-17/0247.html
My version differ in several aspects: it is for 2.4 (vs. 2.6); it do not 
ioremap/unmap page for each transaction.

How about inclusion in 2.4.24?

I am not subscribed to lkml, thus please CC me
(Vladimir Kondratiev <vladimir.kondratiev@intel.com>) in replies.

Vladimir.

[-- Attachment #2: pciexp.patch --]
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Enable PCI Express access method for configuration space
This path includes:
 * access routines itself
 * command line argument "pci=exp" to force PCI Express, similar to "conf1" and "conf2"
 * full 4k config accessed through /proc/bus/pci/...

How it works:

With PCI-E, config space accessed through memory. Each device gets its own 4k memory mapped config,
total 256M for all devices.

At init time, I map whole region to not spent time for mapping later.

For /proc/bus/pci/..., I changed PCI_CFG_SPACE_SIZE to variable and changed it to 4k for PCI-E.

It is tested on 1 platform.

Author: "Vladimir Kondratiev" <vladimir.kondratiev@intel.com> 

diff -bBdur linux-2.4.23/arch/i386/kernel/pci-i386.h linux-2.4.23-pciexp/arch/i386/kernel/pci-i386.h
--- linux-2.4.23/arch/i386/kernel/pci-i386.h	2003-11-28 20:26:19.000000000 +0200
+++ linux-2.4.23-pciexp/arch/i386/kernel/pci-i386.h	2003-12-14 11:08:17.000000000 +0200
@@ -15,6 +15,7 @@
 #define PCI_PROBE_BIOS		0x0001
 #define PCI_PROBE_CONF1		0x0002
 #define PCI_PROBE_CONF2		0x0004
+#define PCI_PROBE_EXP		0x0008
 #define PCI_NO_SORT		0x0100
 #define PCI_BIOS_SORT		0x0200
 #define PCI_NO_CHECKS		0x0400
diff -bBdur linux-2.4.23/arch/i386/kernel/pci-pc.c linux-2.4.23-pciexp/arch/i386/kernel/pci-pc.c
--- linux-2.4.23/arch/i386/kernel/pci-pc.c	2003-11-28 20:26:19.000000000 +0200
+++ linux-2.4.23-pciexp/arch/i386/kernel/pci-pc.c	2003-12-14 18:30:52.000000000 +0200
@@ -20,7 +20,7 @@
 
 #include "pci-i386.h"
 
-unsigned int pci_probe = PCI_PROBE_BIOS | PCI_PROBE_CONF1 | PCI_PROBE_CONF2;
+unsigned int pci_probe = PCI_PROBE_BIOS | PCI_PROBE_CONF1 | PCI_PROBE_CONF2 | PCI_PROBE_EXP;
 
 int pcibios_last_bus = -1;
 struct pci_bus *pci_root_bus = NULL;
@@ -427,6 +427,169 @@
 	pci_conf2_write_config_dword
 };
 
+/**
+ * PCI Express routines
+ * "Vladimir Kondratiev" <vladimir.kondratiev@intel.com>
+ */
+/**
+ * RRBAR (memory base for PCI-E config space) resides here.
+ * Initialized to default address. Actually, it is platform specific, and
+ * value may vary.
+ * I don't know how to detect it properly, it is chipset specific.
+ */
+static u32 rrbar_phys=0xe0000000UL;
+/**
+ * RRBAR is always 256M
+ */
+static u32 rrbar_size=0x10000000UL;
+/**
+ * Virtual address for RRBAR
+ */
+static void* rrbar_virt=NULL;
+/**
+ * It used to be #define, but I am going to change it.
+ */
+extern int PCI_CFG_SPACE_SIZE;
+
+union pci_exp_data {
+    u32 l;
+    u16 w[2];
+    u8  b[4];
+} __attribute__((packed));
+
+/**
+ * Initializes PCI Express method for config space access.
+ * 
+ * There is no standard method to recognize presence of PCI Express,
+ * thus we will assume it is PCI-E, and rely on sanity check to
+ * deassert PCI-E presense. If PCI-E not present,
+ * there is no physical RAM on RRBAR address, and we should read
+ * something like 0xff.
+ * 
+ * Creates mapping for whole 256M area.
+ * 
+ * @return 1 if OK, 0 if error
+ */
+static int pci_express_init(void)
+{
+    /* TODO: check PCI-Ex presense */
+    rrbar_virt=ioremap(rrbar_phys,rrbar_size);
+    if (!rrbar_virt) return 0;
+    return 1;
+}
+
+/**
+ * Shuts down PCI-E resources.
+ */
+static void pci_express_fini(void)
+{
+    if (rrbar_virt) {
+        iounmap(rrbar_virt);
+    }
+}
+
+static int pci_exp_read (int seg, int bus, int dev, int fn, int reg, int len, u32 *value)
+{
+    union pci_exp_data d;
+    void* addr=rrbar_virt+(bus << 20)+(dev << 15)+(fn << 12)+(reg &~ 3);
+    d.l=readl(addr);
+    switch (len) {
+    case 1:
+        *value=d.b[reg & 3];
+        break;
+    case 2:
+        *value=d.w[(reg & 2)>>1];
+        break;
+    case 4:
+        *value=d.l;
+        break;
+    }
+	return 0;
+}
+
+static int pci_exp_write (int seg, int bus, int dev, int fn, int reg, int len, u32 value)
+{
+    void* addr=rrbar_virt+(bus << 20)+(dev << 15)+(fn << 12)+(reg &~ 3);
+	switch (len) {
+    case 1:
+    case 2:
+        {
+            unsigned long flags;
+            union pci_exp_data d;
+            spin_lock_irqsave(&pci_config_lock, flags);
+            switch (len) {
+            case 1:
+                d.l=readl(addr);
+                d.b[reg & 3]=value;
+                break;
+            case 2:
+                d.l=readl(addr);
+                d.w[(reg & 2)>>1]=value;
+                break;
+            }
+            writel(d.l,addr);
+            spin_unlock_irqrestore(&pci_config_lock, flags);
+        }
+        break;
+    case 4:
+        writel(value,addr);
+        break;
+    }
+	return 0;
+}
+
+static int pci_exp_read_config_byte(struct pci_dev *dev, int where, u8 *value)
+{
+	int result; 
+	u32 data;
+	result = pci_exp_read(0, dev->bus->number, PCI_SLOT(dev->devfn), 
+		PCI_FUNC(dev->devfn), where, 1, &data);
+	*value = (u8)data;
+	return result;
+}
+
+static int pci_exp_read_config_word(struct pci_dev *dev, int where, u16 *value)
+{
+	int result; 
+	u32 data;
+	result = pci_exp_read(0, dev->bus->number, PCI_SLOT(dev->devfn), 
+		PCI_FUNC(dev->devfn), where, 2, &data);
+	*value = (u16)data;
+	return result;
+}
+
+static int pci_exp_read_config_dword(struct pci_dev *dev, int where, u32 *value)
+{
+	return pci_exp_read(0, dev->bus->number, PCI_SLOT(dev->devfn), 
+		PCI_FUNC(dev->devfn), where, 4, value);
+}
+
+static int pci_exp_write_config_byte(struct pci_dev *dev, int where, u8 value)
+{
+	return pci_exp_write(0, dev->bus->number, PCI_SLOT(dev->devfn), 
+		PCI_FUNC(dev->devfn), where, 1, value);
+}
+
+static int pci_exp_write_config_word(struct pci_dev *dev, int where, u16 value)
+{
+	return pci_exp_write(0, dev->bus->number, PCI_SLOT(dev->devfn), 
+		PCI_FUNC(dev->devfn), where, 2, value);
+}
+
+static int pci_exp_write_config_dword(struct pci_dev *dev, int where, u32 value)
+{
+	return pci_exp_write(0, dev->bus->number, PCI_SLOT(dev->devfn), 
+		PCI_FUNC(dev->devfn), where, 4, value);
+}
+
+static struct pci_ops pci_express_conf = {
+	pci_exp_read_config_byte,
+	pci_exp_read_config_word,
+	pci_exp_read_config_dword,
+	pci_exp_write_config_byte,
+	pci_exp_write_config_word,
+	pci_exp_write_config_dword
+};
 
 /*
  * Before we decide to use direct hardware access mechanisms, we try to do some
@@ -465,6 +628,21 @@
 
 	__save_flags(flags); __cli();
 
+    /**
+     * Check if PCI-express access work
+     */
+    if (pci_express_init()) {
+        if (pci_sanity_check(&pci_express_conf)) {
+            PCI_CFG_SPACE_SIZE=4096;
+			__restore_flags(flags);
+			printk(KERN_INFO "PCI: Using configuration type PCI Express\n");
+			request_mem_region(rrbar_phys, rrbar_size, "PCI-Express config space");
+			return &pci_express_conf;
+        } else {
+            pci_express_fini();
+        }
+    }
+
 	/*
 	 * Check if configuration type 1 works.
 	 */
@@ -1398,16 +1576,18 @@
 #endif
 
 #ifdef CONFIG_PCI_DIRECT
-	if ((pci_probe & (PCI_PROBE_CONF1 | PCI_PROBE_CONF2)) 
+	if ((pci_probe & (PCI_PROBE_CONF1 | PCI_PROBE_CONF2 | PCI_PROBE_EXP)) 
 		&& (tmp = pci_check_direct())) {
 		pci_root_ops = tmp;
 		if (pci_root_ops == &pci_direct_conf1) {
 			pci_config_read = pci_conf1_read;
 			pci_config_write = pci_conf1_write;
-		}
-		else {
+		} else if (pci_root_ops == &pci_direct_conf2) {
 			pci_config_read = pci_conf2_read;
 			pci_config_write = pci_conf2_write;
+		} else if (pci_root_ops == &pci_express_conf) {
+			pci_config_read = pci_exp_read;
+			pci_config_write = pci_exp_write;
 		}
 	}
 #endif
@@ -1489,6 +1669,10 @@
 		pci_probe = PCI_PROBE_CONF2 | PCI_NO_CHECKS;
 		return NULL;
 	}
+	else if (!strcmp(str, "exp")) {
+		pci_probe = PCI_PROBE_EXP | PCI_NO_CHECKS;
+		return NULL;
+	}
 #endif
 	else if (!strcmp(str, "rom")) {
 		pci_probe |= PCI_ASSIGN_ROMS;
diff -bBdur linux-2.4.23/drivers/pci/proc.c linux-2.4.23-pciexp/drivers/pci/proc.c
--- linux-2.4.23/drivers/pci/proc.c	2002-11-29 01:53:14.000000000 +0200
+++ linux-2.4.23-pciexp/drivers/pci/proc.c	2003-12-14 14:18:58.000000000 +0200
@@ -16,7 +16,7 @@
 #include <asm/uaccess.h>
 #include <asm/byteorder.h>
 
-#define PCI_CFG_SPACE_SIZE 256
+int PCI_CFG_SPACE_SIZE=256;
 
 static loff_t
 proc_bus_pci_lseek(struct file *file, loff_t off, int whence)