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66MHz PCI flag from commandline

PATCH New Tim Hockin 1 participant 1 message Jun 1, 2001 1 message not in the archive PCI

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Tim Hockin

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PATCH 1/1 66MHz PCI flag from commandline

Martin,

We spoke a while back about a pcispeed= command line param to set the PCI busspeed values (for later querying, if needed). Attached is my patch to implement the feature we agreed upon. It is against linux-2.4.5.

Below is our previous discussion, as a refresher :). Please let me know if this is not suitable for general inclusion in the kernel, and I'll try to make it so.

Tim

(cc: lkml, alan)

Quoted 6 lines · Martin Mares
Quoted 1 line

What do you think of my pcispeed=0:33,2:66 idea?

anything -- the 33/66 MHz values from the PCI specs are only upper limits), I'll welcome this option, but otherwise I'd rather like to use the measuring code in IDE driver as it requires no user intervention to get the right timing.

Signature · 4 lines
Tim Hockin
Systems Software Engineer
Sun Microsystems, Cobalt Server Appliances
[email protected]
drivers/pci/pci.c +76 -1
diff -ruN dist-2.4.5/drivers/pci/pci.c cobalt-2.4.5/drivers/pci/pci.c
@@ -20,6 +20,7 @@
 #include <linux/ioport.h>
 #include <linux/spinlock.h>
 #include <linux/pm.h>
+#include <linux/ctype.h>
 #include <linux/kmod.h>		/* for hotplug_path */
 #include <linux/bitops.h>
 

@@ -37,6 +38,8 @@
 LIST_HEAD(pci_root_buses);
 LIST_HEAD(pci_devices);
 
+static int get_bus_speed(struct pci_bus *bus);
+
 /**
  * pci_find_slot - locate PCI device from a given PCI slot
  * @bus: number of PCI bus on which desired PCI device resides

@@ -928,6 +931,7 @@
 	child->number = child->secondary = busnr;
 	child->primary = parent->secondary;
 	child->subordinate = 0xff;
+	child->bus_speed = get_bus_speed(child);
 
 	/* Set up default resource pointers.. */
 	for (i = 0; i < 4; i++)

@@ -1110,8 +1114,19 @@
 		return NULL;
 
 	/* some broken boards return 0 or ~0 if a slot is empty: */
-	if (l == 0xffffffff || l == 0x00000000 || l == 0x0000ffff || l == 0xffff0000)
+	if (l == 0xffffffff || l == 0x00000000 
+	 || l == 0x0000ffff || l == 0xffff0000) {
+		/*
+		 * host/pci and pci/pci bridges will set Received Master Abort
+		 * (bit 13) on failed configuration access (happens when
+		 * searching for devices).  To be safe, clear the status
+		 * register.
+		 */
+		unsigned short st;
+		pci_read_config_word(temp, PCI_STATUS, &st);
+		pci_write_config_word(temp, PCI_STATUS, st);
 		return NULL;
+	}
 
 	dev = kmalloc(sizeof(*dev), GFP_KERNEL);
 	if (!dev)

@@ -1239,6 +1254,7 @@
 	list_add_tail(&b->node, &pci_root_buses);
 
 	b->number = b->secondary = bus;
+	b->bus_speed = get_bus_speed(b);
 	b->resource[0] = &ioport_resource;
 	b->resource[1] = &iomem_resource;
 	return b;

@@ -1739,7 +1755,66 @@
 	return 1;
 }
 
+#define MAX_OVERRIDES 256
+static int pci_speed_overrides[MAX_OVERRIDES] __initdata;
+
+static int __init get_bus_speed(struct pci_bus *bus)
+{
+	if (!bus) {
+		return -1;
+	}
+
+	if (pci_speed_overrides[bus->number]) {
+		return pci_speed_overrides[bus->number];
+	} else {
+		/* printk("PCI: assuming 33 MHz for bus %d\n", bus->number); */
+		return 33;
+	}
+}
+
+/* handle pcispeed=0:33,1:66 parameter (speed=0 means unknown) */
+static int __init pci_speed_setup(char *str)
+{
+        while (str) {
+                char *k = strchr(str, ',');
+                if (k) {
+                        *k++ = '\0';
+		}
+
+                if (*str) {
+                        int bus;
+                        int speed;
+                        char *endp;
+
+			if (!isdigit(*str)) {
+				printk("PCI: bad bus number for "
+					"pcispeed parameter\n");
+				str = k;
+				continue;
+			}
+                        bus = simple_strtoul(str, &endp, 0);
+
+                        if (!*endp || !isdigit(*(++endp))) {
+				printk("PCI: bad speed for "
+					"pcispeed parameter\n");
+				str = k;
+				continue;
+			}
+			speed = simple_strtoul(endp, NULL, 0);
+			pci_speed_overrides[bus] = speed;
+			printk("PCI: setting bus %d speed to %d MHz\n",
+				bus, speed);
+
+			str = k;
+		} else {
+			break;
+		}
+	}
+	return 1;
+}
+
 __setup("pci=", pci_setup);
+__setup("pcispeed=", pci_speed_setup);
 
 
 EXPORT_SYMBOL(pci_read_config_byte);
include/linux/pci.h +2 -1
diff -ruN dist-2.4.5/include/linux/pci.h cobalt-2.4.5/include/linux/pci.h
@@ -1,5 +1,5 @@
 /*
- *	$Id: pci.h,v 1.87 1998/10/11 15:13:12 mj Exp $
+ *	$Id: pci.h,v 1.1.1.3 2001/04/04 20:08:09 thockin Exp $
  *
  *	PCI defines and function prototypes
  *	Copyright 1994, Drew Eckhardt

@@ -413,6 +413,7 @@
 	unsigned char	primary;	/* number of primary bridge */
 	unsigned char	secondary;	/* number of secondary bridge */
 	unsigned char	subordinate;	/* max number of subordinate buses */
+	int		bus_speed;	/* the speed of this PCI segment */
 
 	char		name[48];
 	unsigned short	vendor;