PCI: Pull PCI 'latency timer' setup up into the core

The 'latency timer' of PCI devices, both Type 0 and Type 1,
is setup in architecture-specific code [see: 'pcibios_set_master()'].
There are two approaches being taken by all the architectures - check
if the 'latency timer' is currently set between 16 and 255 and if not
bring it within bounds, or, do nothing (and then there is the
gratuitously different PA-RISC implementation).

There is nothing architecture-specific about PCI's 'latency timer' so
this patch pulls its setup functionality up into the PCI core by
creating a generic 'pcibios_set_master()' function using the '__weak'
attribute which can be used by all architectures as a default which,
if necessary, can then be over-ridden by architecture-specific code.

No functional change.
Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

arch/blackfin/include/asm/pci.h

@@ -10,10 +10,6 @@
 #define PCIBIOS_MIN_IO 0x00001000
 #define PCIBIOS_MIN_MEM 0x10000000
 
-static inline void pcibios_set_master(struct pci_dev *dev)
-{
-	/* No special bus mastering setup handling */
-}
 static inline void pcibios_penalize_isa_irq(int irq)
 {
 	/* We don't do dynamic PCI IRQ allocation */

arch/frv/mb93090-mb00/pci-frv.c

@@ -195,12 +195,6 @@ void __init pcibios_resource_survey(void)
 	pcibios_assign_resources();
 }
 
-/*
- *  If we set up a device for bus mastering, we need to check the latency
- *  timer as certain crappy BIOSes forget to set it properly.
- */
-unsigned int pcibios_max_latency = 255;
-
 void pcibios_set_master(struct pci_dev *dev)
 {
 	u8 lat;

arch/frv/mb93090-mb00/pci-frv.h

@@ -26,8 +26,6 @@ extern unsigned int __nongpreldata pci_probe;
 
 /* pci-frv.c */
 
-extern unsigned int pcibios_max_latency;
-
 void pcibios_resource_survey(void);
 
 /* pci-vdk.c */

arch/h8300/include/asm/pci.h

@@ -9,11 +9,6 @@
 
 #define pcibios_assign_all_busses()	0
 
-static inline void pcibios_set_master(struct pci_dev *dev)
-{
-	/* No special bus mastering setup handling */
-}
-
 static inline void pcibios_penalize_isa_irq(int irq, int active)
 {
 	/* We don't do dynamic PCI IRQ allocation */

arch/mips/pci/pci.c

@@ -205,12 +205,6 @@ static int pcibios_enable_resources(struct pci_dev *dev, int mask)
 	return 0;
 }
 
-/*
- *  If we set up a device for bus mastering, we need to check the latency
- *  timer as certain crappy BIOSes forget to set it properly.
- */
-static unsigned int pcibios_max_latency = 255;
-
 void pcibios_set_master(struct pci_dev *dev)
 {
 	u8 lat;

arch/mn10300/unit-asb2305/pci-asb2305.c

@@ -213,12 +213,6 @@ void __init pcibios_resource_survey(void)
 	pcibios_allocate_resources(1);
 }
 
-/*
- *  If we set up a device for bus mastering, we need to check the latency
- *  timer as certain crappy BIOSes forget to set it properly.
- */
-unsigned int pcibios_max_latency = 255;
-
 void pcibios_set_master(struct pci_dev *dev)
 {
 	u8 lat;

arch/mn10300/unit-asb2305/pci-asb2305.h

@@ -31,8 +31,6 @@ extern unsigned int pci_probe;
 
 /* pci-asb2305.c */
 
-extern unsigned int pcibios_max_latency;
-
 extern void pcibios_resource_survey(void);
 
 /* pci.c */

arch/sh/drivers/pci/pci.c

@@ -243,12 +243,6 @@ int pcibios_enable_device(struct pci_dev *dev, int mask)
 	return pci_enable_resources(dev, mask);
 }
 
-/*
- *  If we set up a device for bus mastering, we need to check and set
- *  the latency timer as it may not be properly set.
- */
-static unsigned int pcibios_max_latency = 255;
-
 void pcibios_set_master(struct pci_dev *dev)
 {
 	u8 lat;

arch/x86/include/asm/pci_x86.h

@@ -44,8 +44,6 @@ enum pci_bf_sort_state {
 
 /* pci-i386.c */
 
-extern unsigned int pcibios_max_latency;
-
 void pcibios_resource_survey(void);
 void pcibios_set_cache_line_size(void);
 

arch/x86/pci/i386.c

@@ -254,12 +254,6 @@ void __init pcibios_resource_survey(void)
  */
 fs_initcall(pcibios_assign_resources);
 
-/*
- *  If we set up a device for bus mastering, we need to check the latency
- *  timer as certain crappy BIOSes forget to set it properly.
- */
-unsigned int pcibios_max_latency = 255;
-
 void pcibios_set_master(struct pci_dev *dev)
 {
 	u8 lat;

drivers/pci/pci.c

@@ -88,6 +88,12 @@ enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_TUNE_OFF;
 u8 pci_dfl_cache_line_size __devinitdata = L1_CACHE_BYTES >> 2;
 u8 pci_cache_line_size;
 
+/*
+ * If we set up a device for bus mastering, we need to check the latency
+ * timer as certain BIOSes forget to set it properly.
+ */
+unsigned int pcibios_max_latency = 255;
+
 /**
  * pci_bus_max_busnr - returns maximum PCI bus number of given bus' children
  * @bus: pointer to PCI bus structure to search
@@ -2595,6 +2601,29 @@ static void __pci_set_master(struct pci_dev *dev, bool enable)
 	dev->is_busmaster = enable;
 }
 
+/**
+ * pcibios_set_master - enable PCI bus-mastering for device dev
+ * @dev: the PCI device to enable
+ *
+ * Enables PCI bus-mastering for the device.  This is the default
+ * implementation.  Architecture specific implementations can override
+ * this if necessary.
+ */
+void __weak pcibios_set_master(struct pci_dev *dev)
+{
+	u8 lat;
+
+	pci_read_config_byte(dev, PCI_LATENCY_TIMER, &lat);
+	if (lat < 16)
+		lat = (64 <= pcibios_max_latency) ? 64 : pcibios_max_latency;
+	else if (lat > pcibios_max_latency)
+		lat = pcibios_max_latency;
+	else
+		return;
+	dev_printk(KERN_DEBUG, &dev->dev, "setting latency timer to %d\n", lat);
+	pci_write_config_byte(dev, PCI_LATENCY_TIMER, lat);
+}
+
 /**
  * pci_set_master - enables bus-mastering for device dev
  * @dev: the PCI device to enable

include/linux/pci.h

@@ -795,8 +795,11 @@ static inline int pci_is_managed(struct pci_dev *pdev)
 }
 
 void pci_disable_device(struct pci_dev *dev);
+
+extern unsigned int pcibios_max_latency;
 void pci_set_master(struct pci_dev *dev);
 void pci_clear_master(struct pci_dev *dev);
+
 int pci_set_pcie_reset_state(struct pci_dev *dev, enum pcie_reset_state state);
 int pci_set_cacheline_size(struct pci_dev *dev);
 #define HAVE_PCI_SET_MWI