Messages in this thread Patch in this message | | | From | Ricardo Neri <> | Subject | [RFC PATCH v4 04/21] x86/hpet: Add hpet_set_comparator() for periodic and one-shot modes | Date | Thu, 23 May 2019 18:16:06 -0700 |
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Instead of setting the timer period directly in hpet_set_periodic(), add a new helper function hpet_set_comparator() that only sets the accumulator and comparator. hpet_set_periodic() will only prepare the timer for periodic mode and leave the expiration programming to hpet_set_comparator().
This new function can also be used by other components (e.g., the HPET- based hardlockup detector) which also need to configure HPET timers. Thus, add its declaration into the hpet header file.
Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ashok Raj <ashok.raj@intel.com> Cc: Andi Kleen <andi.kleen@intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> Cc: Stephane Eranian <eranian@google.com> Cc: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com> Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com> Cc: x86@kernel.org Originally-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> --- arch/x86/include/asm/hpet.h | 1 + arch/x86/kernel/hpet.c | 57 +++++++++++++++++++++++++++++-------- 2 files changed, 46 insertions(+), 12 deletions(-)
diff --git a/arch/x86/include/asm/hpet.h b/arch/x86/include/asm/hpet.h index f132fbf984d4..e7098740f5ee 100644 --- a/arch/x86/include/asm/hpet.h +++ b/arch/x86/include/asm/hpet.h @@ -102,6 +102,7 @@ extern int hpet_rtc_timer_init(void); extern irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id); extern int hpet_register_irq_handler(rtc_irq_handler handler); extern void hpet_unregister_irq_handler(rtc_irq_handler handler); +extern void hpet_set_comparator(int num, unsigned int cmp, unsigned int period); #endif /* CONFIG_HPET_EMULATE_RTC */ diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index 5e86e024c489..1723d55219e8 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -290,6 +290,47 @@ static void hpet_legacy_clockevent_register(void) printk(KERN_DEBUG "hpet clockevent registered\n"); } +/** + * hpet_set_comparator() - Helper function for setting comparator register + * @num: The timer ID + * @cmp: The value to be written to the comparator/accumulator + * @period: The value to be written to the period (0 = oneshot mode) + * + * Helper function for updating comparator, accumulator and period values. + * + * In periodic mode, HPET needs HPET_TN_SETVAL to be set before writing + * to the Tn_CMP to update the accumulator. Then, HPET needs a second + * write (with HPET_TN_SETVAL cleared) to Tn_CMP to set the period. + * The HPET_TN_SETVAL bit is automatically cleared after the first write. + * + * For one-shot mode, HPET_TN_SETVAL does not need to be set. + * + * See the following documents: + * - Intel IA-PC HPET (High Precision Event Timers) Specification + * - AMD-8111 HyperTransport I/O Hub Data Sheet, Publication # 24674 + */ +void hpet_set_comparator(int num, unsigned int cmp, unsigned int period) +{ + if (period) { + unsigned int v = hpet_readl(HPET_Tn_CFG(num)); + + hpet_writel(v | HPET_TN_SETVAL, HPET_Tn_CFG(num)); + } + + hpet_writel(cmp, HPET_Tn_CMP(num)); + + if (!period) + return; + + /* + * This delay is seldom used: never in one-shot mode and in periodic + * only when reprogramming the timer. + */ + udelay(1); + hpet_writel(period, HPET_Tn_CMP(num)); +} +EXPORT_SYMBOL_GPL(hpet_set_comparator); + static int hpet_set_periodic(struct clock_event_device *evt, int timer) { unsigned int cfg, cmp, now; @@ -301,19 +342,11 @@ static int hpet_set_periodic(struct clock_event_device *evt, int timer) now = hpet_readl(HPET_COUNTER); cmp = now + (unsigned int)delta; cfg = hpet_readl(HPET_Tn_CFG(timer)); - cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL | - HPET_TN_32BIT; + cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_32BIT; hpet_writel(cfg, HPET_Tn_CFG(timer)); - hpet_writel(cmp, HPET_Tn_CMP(timer)); - udelay(1); - /* - * HPET on AMD 81xx needs a second write (with HPET_TN_SETVAL - * cleared) to T0_CMP to set the period. The HPET_TN_SETVAL - * bit is automatically cleared after the first write. - * (See AMD-8111 HyperTransport I/O Hub Data Sheet, - * Publication # 24674) - */ - hpet_writel((unsigned int)delta, HPET_Tn_CMP(timer)); + + hpet_set_comparator(timer, cmp, (unsigned int)delta); + hpet_start_counter(); hpet_print_config(); -- 2.17.1
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