From 96c5590058d7fded14f43af2ab521436cecf3125 Mon Sep 17 00:00:00 2001 From: Myron Stowe Date: Fri, 28 Oct 2011 15:48:38 -0600 Subject: 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 Signed-off-by: Jesse Barnes --- drivers/pci/pci.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) (limited to 'drivers') 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 @@ -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 -- cgit v1.2.3