PCI: determine CLS more intelligently

Till now, CLS has been determined either by arch code or as
L1_CACHE_BYTES.  Only x86 and ia64 set CLS explicitly and x86 doesn't
always get it right.  On most configurations, the chance is that
firmware configures the correct value during boot.

This patch makes pci_init() determine CLS by looking at what firmware
has configured.  It scans all devices and if all non-zero values
agree, the value is used.  If none is configured or there is a
disagreement, pci_dfl_cache_line_size is used.  arch can set the dfl
value (via PCI_CACHE_LINE_BYTES or pci_dfl_cache_line_size) or
override the actual one.

ia64, x86 and sparc64 updated to set the default cls instead of the
actual one.

While at it, declare pci_cache_line_size and pci_dfl_cache_line_size
in pci.h and drop private declarations from arch code.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NDavid Miller <davem@davemloft.net>
Acked-by: NGreg KH <gregkh@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

arch/ia64/pci/pci.c

@@ -720,9 +720,6 @@ int ia64_pci_legacy_write(struct pci_bus *bus, u16 port, u32 val, u8 size)
 	return ret;
 }
 
-/* It's defined in drivers/pci/pci.c */
-extern u8 pci_cache_line_size;
-
 /**
  * set_pci_cacheline_size - determine cacheline size for PCI devices
  *
@@ -731,7 +728,7 @@ extern u8 pci_cache_line_size;
  *
  * Code mostly taken from arch/ia64/kernel/palinfo.c:cache_info().
  */
-static void __init set_pci_cacheline_size(void)
+static void __init set_pci_dfl_cacheline_size(void)
 {
 	unsigned long levels, unique_caches;
 	long status;
@@ -751,7 +748,7 @@ static void __init set_pci_cacheline_size(void)
 			"(status=%ld)\n", __func__, status);
 		return;
 	}
-	pci_cache_line_size = (1 << cci.pcci_line_size) / 4;
+	pci_dfl_cache_line_size = (1 << cci.pcci_line_size) / 4;
 }
 
 u64 ia64_dma_get_required_mask(struct device *dev)
@@ -782,7 +779,7 @@ EXPORT_SYMBOL_GPL(dma_get_required_mask);
 
 static int __init pcibios_init(void)
 {
-	set_pci_cacheline_size();
+	set_pci_dfl_cacheline_size();
 	return 0;
 }
 

arch/x86/pci/common.c

@@ -410,8 +410,6 @@ struct pci_bus * __devinit pcibios_scan_root(int busnum)
 	return bus;
 }
 
-extern u8 pci_cache_line_size;
-
 int __init pcibios_init(void)
 {
 	struct cpuinfo_x86 *c = &boot_cpu_data;
@@ -426,11 +424,11 @@ int __init pcibios_init(void)
 	 * and P4. It's also good for 386/486s (which actually have 16)
 	 * as quite a few PCI devices do not support smaller values.
 	 */
-	pci_cache_line_size = 32 >> 2;
+	pci_dfl_cache_line_size = 32 >> 2;
 	if (c->x86 >= 6 && c->x86_vendor == X86_VENDOR_AMD)
-		pci_cache_line_size = 64 >> 2;	/* K7 & K8 */
+		pci_dfl_cache_line_size = 64 >> 2;	/* K7 & K8 */
 	else if (c->x86 > 6 && c->x86_vendor == X86_VENDOR_INTEL)
-		pci_cache_line_size = 128 >> 2;	/* P4 */
+		pci_dfl_cache_line_size = 128 >> 2;	/* P4 */
 
 	pcibios_resource_survey();
 

drivers/pci/pci.c

@@ -47,6 +47,19 @@ unsigned long pci_cardbus_mem_size = DEFAULT_CARDBUS_MEM_SIZE;
 unsigned long pci_hotplug_io_size  = DEFAULT_HOTPLUG_IO_SIZE;
 unsigned long pci_hotplug_mem_size = DEFAULT_HOTPLUG_MEM_SIZE;
 
+#ifndef PCI_CACHE_LINE_BYTES
+#define PCI_CACHE_LINE_BYTES L1_CACHE_BYTES
+#endif
+
+/*
+ * The default CLS is used if arch didn't set CLS explicitly and not
+ * all pci devices agree on the same value.  Arch can override either
+ * the dfl or actual value as it sees fit.  Don't forget this is
+ * measured in 32-bit words, not bytes.
+ */
+u8 pci_dfl_cache_line_size __initdata = PCI_CACHE_LINE_BYTES >> 2;
+u8 pci_cache_line_size;
+
 /**
  * pci_bus_max_busnr - returns maximum PCI bus number of given bus' children
  * @bus: pointer to PCI bus structure to search
@@ -1883,14 +1896,6 @@ void pci_clear_mwi(struct pci_dev *dev)
 
 #else
 
-#ifndef PCI_CACHE_LINE_BYTES
-#define PCI_CACHE_LINE_BYTES L1_CACHE_BYTES
-#endif
-
-/* This can be overridden by arch code. */
-/* Don't forget this is measured in 32-bit words, not bytes */
-u8 pci_cache_line_size = PCI_CACHE_LINE_BYTES / 4;
-
 /**
  * pci_set_cacheline_size - ensure the CACHE_LINE_SIZE register is programmed
  * @dev: the PCI device for which MWI is to be enabled

drivers/pci/quirks.c

@@ -2595,9 +2595,37 @@ void pci_fixup_device(enum pci_fixup_pass pass, struct pci_dev *dev)
 static int __init pci_apply_final_quirks(void)
 {
 	struct pci_dev *dev = NULL;
+	u8 cls = 0;
+	u8 tmp;
+
+	if (pci_cache_line_size)
+		printk(KERN_DEBUG "PCI: CLS %u bytes\n",
+		       pci_cache_line_size << 2);
 
 	while ((dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, dev)) != NULL) {
 		pci_fixup_device(pci_fixup_final, dev);
+		/*
+		 * If arch hasn't set it explicitly yet, use the CLS
+		 * value shared by all PCI devices.  If there's a
+		 * mismatch, fall back to the default value.
+		 */
+		if (!pci_cache_line_size) {
+			pci_read_config_byte(dev, PCI_CACHE_LINE_SIZE, &tmp);
+			if (!cls)
+				cls = tmp;
+			if (!tmp || cls == tmp)
+				continue;
+
+			printk(KERN_DEBUG "PCI: CLS mismatch (%u != %u), "
+			       "using %u bytes\n", cls << 2, tmp << 2,
+			       pci_dfl_cache_line_size << 2);
+			pci_cache_line_size = pci_dfl_cache_line_size;
+		}
+	}
+	if (!pci_cache_line_size) {
+		printk(KERN_DEBUG "PCI: CLS %u bytes, default %u\n",
+		       cls << 2, pci_dfl_cache_line_size << 2);
+		pci_cache_line_size = cls;
 	}
 
 	return 0;

include/linux/pci.h

@@ -1246,6 +1246,8 @@ extern int pci_pci_problems;
 
 extern unsigned long pci_cardbus_io_size;
 extern unsigned long pci_cardbus_mem_size;
+extern u8 pci_dfl_cache_line_size;
+extern u8 pci_cache_line_size;
 
 extern unsigned long pci_hotplug_io_size;
 extern unsigned long pci_hotplug_mem_size;