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authorMyron Stowe <mstowe@redhat.com>2011-10-28 15:48:38 -0600
committerJesse Barnes <jbarnes@virtuousgeek.org>2012-01-06 12:10:42 -0800
commit96c5590058d7fded14f43af2ab521436cecf3125 (patch)
tree673577f86b1ee8886c27cc86333fdfdc6cc783ac /drivers/pci
parent9cdce18d6f0baae53f012fb3f50e66e7ff24c509 (diff)
downloadlinux-96c5590058d7fded14f43af2ab521436cecf3125.tar.bz2
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>
Diffstat (limited to 'drivers/pci')
-rw-r--r--drivers/pci/pci.c29
1 files changed, 29 insertions, 0 deletions
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 924193ef4fe1..f9abe84cf5e0 100644
--- a/drivers/pci/pci.c
+++ b/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
@@ -2596,6 +2602,29 @@ static void __pci_set_master(struct pci_dev *dev, bool 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
*