diff options
Diffstat (limited to 'drivers/sn/ioc4.c')
| -rw-r--r-- | drivers/sn/ioc4.c | 128 |
1 files changed, 128 insertions, 0 deletions
diff --git a/drivers/sn/ioc4.c b/drivers/sn/ioc4.c index 70862d72ea9..ea75b3d0612 100644 --- a/drivers/sn/ioc4.c +++ b/drivers/sn/ioc4.c @@ -29,7 +29,26 @@ #include <linux/module.h> #include <linux/pci.h> #include <linux/ioc4.h> +#include <linux/mmtimer.h> +#include <linux/rtc.h> #include <linux/rwsem.h> +#include <asm/sn/addrs.h> +#include <asm/sn/clksupport.h> +#include <asm/sn/shub_mmr.h> + +/*************** + * Definitions * + ***************/ + +/* Tweakable values */ + +/* PCI bus speed detection/calibration */ +#define IOC4_CALIBRATE_COUNT 63 /* Calibration cycle period */ +#define IOC4_CALIBRATE_CYCLES 256 /* Average over this many cycles */ +#define IOC4_CALIBRATE_DISCARD 2 /* Discard first few cycles */ +#define IOC4_CALIBRATE_LOW_MHZ 25 /* Lower bound on bus speed sanity */ +#define IOC4_CALIBRATE_HIGH_MHZ 75 /* Upper bound on bus speed sanity */ +#define IOC4_CALIBRATE_DEFAULT_MHZ 66 /* Assumed if sanity check fails */ /************************ * Submodule management * @@ -101,6 +120,112 @@ ioc4_unregister_submodule(struct ioc4_submodule *is) * Device management * *********************/ +#define IOC4_CALIBRATE_LOW_LIMIT \ + (1000*IOC4_EXTINT_COUNT_DIVISOR/IOC4_CALIBRATE_LOW_MHZ) +#define IOC4_CALIBRATE_HIGH_LIMIT \ + (1000*IOC4_EXTINT_COUNT_DIVISOR/IOC4_CALIBRATE_HIGH_MHZ) +#define IOC4_CALIBRATE_DEFAULT \ + (1000*IOC4_EXTINT_COUNT_DIVISOR/IOC4_CALIBRATE_DEFAULT_MHZ) + +#define IOC4_CALIBRATE_END \ + (IOC4_CALIBRATE_CYCLES + IOC4_CALIBRATE_DISCARD) + +#define IOC4_INT_OUT_MODE_TOGGLE 0x7 /* Toggle INT_OUT every COUNT+1 ticks */ + +/* Determines external interrupt output clock period of the PCI bus an + * IOC4 is attached to. This value can be used to determine the PCI + * bus speed. + * + * IOC4 has a design feature that various internal timers are derived from + * the PCI bus clock. This causes IOC4 device drivers to need to take the + * bus speed into account when setting various register values (e.g. INT_OUT + * register COUNT field, UART divisors, etc). Since this information is + * needed by several subdrivers, it is determined by the main IOC4 driver, + * even though the following code utilizes external interrupt registers + * to perform the speed calculation. + */ +static void +ioc4_clock_calibrate(struct ioc4_driver_data *idd) +{ + extern unsigned long sn_rtc_cycles_per_second; + union ioc4_int_out int_out; + union ioc4_gpcr gpcr; + unsigned int state, last_state = 1; + uint64_t start = 0, end, period; + unsigned int count = 0; + + /* Enable output */ + gpcr.raw = 0; + gpcr.fields.dir = IOC4_GPCR_DIR_0; + gpcr.fields.int_out_en = 1; + writel(gpcr.raw, &idd->idd_misc_regs->gpcr_s.raw); + + /* Reset to power-on state */ + writel(0, &idd->idd_misc_regs->int_out.raw); + mmiowb(); + + printk(KERN_INFO + "%s: Calibrating PCI bus speed " + "for pci_dev %s ... ", __FUNCTION__, pci_name(idd->idd_pdev)); + /* Set up square wave */ + int_out.raw = 0; + int_out.fields.count = IOC4_CALIBRATE_COUNT; + int_out.fields.mode = IOC4_INT_OUT_MODE_TOGGLE; + int_out.fields.diag = 0; + writel(int_out.raw, &idd->idd_misc_regs->int_out.raw); + mmiowb(); + + /* Check square wave period averaged over some number of cycles */ + do { + int_out.raw = readl(&idd->idd_misc_regs->int_out.raw); + state = int_out.fields.int_out; + if (!last_state && state) { + count++; + if (count == IOC4_CALIBRATE_END) { + end = rtc_time(); + break; + } else if (count == IOC4_CALIBRATE_DISCARD) + start = rtc_time(); + } + last_state = state; + } while (1); + + /* Calculation rearranged to preserve intermediate precision. + * Logically: + * 1. "end - start" gives us number of RTC cycles over all the + * square wave cycles measured. + * 2. Divide by number of square wave cycles to get number of + * RTC cycles per square wave cycle. + * 3. Divide by 2*(int_out.fields.count+1), which is the formula + * by which the IOC4 generates the square wave, to get the + * number of RTC cycles per IOC4 INT_OUT count. + * 4. Divide by sn_rtc_cycles_per_second to get seconds per + * count. + * 5. Multiply by 1E9 to get nanoseconds per count. + */ + period = ((end - start) * 1000000000) / + (IOC4_CALIBRATE_CYCLES * 2 * (IOC4_CALIBRATE_COUNT + 1) + * sn_rtc_cycles_per_second); + + /* Bounds check the result. */ + if (period > IOC4_CALIBRATE_LOW_LIMIT || + period < IOC4_CALIBRATE_HIGH_LIMIT) { + printk("failed. Assuming PCI clock ticks are %d ns.\n", + IOC4_CALIBRATE_DEFAULT / IOC4_EXTINT_COUNT_DIVISOR); + period = IOC4_CALIBRATE_DEFAULT; + } else { + printk("succeeded. PCI clock ticks are %ld ns.\n", + period / IOC4_EXTINT_COUNT_DIVISOR); + } + + /* Remember results. We store the extint clock period rather + * than the PCI clock period so that greater precision is + * retained. Divide by IOC4_EXTINT_COUNT_DIVISOR to get + * PCI clock period. + */ + idd->count_period = period; +} + /* Adds a new instance of an IOC4 card */ static int ioc4_probe(struct pci_dev *pdev, const struct pci_device_id *pci_id) @@ -170,6 +295,9 @@ ioc4_probe(struct pci_dev *pdev, const struct pci_device_id *pci_id) pci_write_config_dword(idd->idd_pdev, PCI_COMMAND, pcmd | PCI_COMMAND_PARITY | PCI_COMMAND_SERR); + /* Determine PCI clock */ + ioc4_clock_calibrate(idd); + /* Disable/clear all interrupts. Need to do this here lest * one submodule request the shared IOC4 IRQ, but interrupt * is generated by a different subdevice. |