From mboxrd@z Thu Jan 1 00:00:00 1970 From: Carsten Emde Subject: [PATCH 1/1] Clocksource: Add sched_clock to Atmel TCB clocksource Date: Tue, 02 Jun 2015 15:42:34 +0200 Message-ID: <20150602134631.969367833@osadl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: RT-users , Carsten Emde To: Sebastian Andrzej Siewior Return-path: Received: from toro.web-alm.net ([62.245.132.31]:54851 "EHLO toro.web-alm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753607AbbFBNrF (ORCPT ); Tue, 2 Jun 2015 09:47:05 -0400 Content-Disposition: inline; filename=drivers-clocksource-tcb-register-sched-clock.patch Sender: linux-rt-users-owner@vger.kernel.org List-ID: The default sched_clock provides a maximum resolution of 1 ms which normally is not sufficient to investigate scheduling related irregularities - more so, if a low-latency or even a real-time kernel is used. Therefore, register the Atmel TCB clocksource that provides a resolution of 63 ns as sched_clock. Signed-off-by: Carsten Emde --- drivers/clocksource/tcb_clksrc.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) Index: linux-3.18.13-rt10-r7s4/drivers/clocksource/tcb_clksrc.c =================================================================== --- linux-3.18.13-rt10-r7s4.orig/drivers/clocksource/tcb_clksrc.c +++ linux-3.18.13-rt10-r7s4/drivers/clocksource/tcb_clksrc.c @@ -10,6 +10,7 @@ #include #include #include +#include /* @@ -40,6 +41,7 @@ */ static void __iomem *tcaddr; +static cycle_t (*do_sched_clock_get_cycles)(struct clocksource *cs); static cycle_t tc_get_cycles(struct clocksource *cs) { @@ -61,6 +63,13 @@ static cycle_t tc_get_cycles32(struct cl return __raw_readl(tcaddr + ATMEL_TC_REG(0, CV)); } +u64 sched_clock_get_cycles(void) +{ + struct clocksource *cs = NULL; + + return (u64) do_sched_clock_get_cycles(cs); +} + static struct clocksource clksrc = { .name = "tcb_clksrc", .rating = 200, @@ -273,6 +282,7 @@ static int __init tcb_clksrc_init(void) int clk32k_divisor_idx = -1; int i; int ret; + unsigned long flags; tc = atmel_tc_alloc(CONFIG_ATMEL_TCB_CLKSRC_BLOCK); if (!tc) { @@ -339,6 +349,11 @@ static int __init tcb_clksrc_init(void) if (ret) goto err_disable_t1; + do_sched_clock_get_cycles = clksrc.read; + local_irq_save(flags); + sched_clock_register(sched_clock_get_cycles, 32, divided_rate); + local_irq_restore(flags); + /* channel 2: periodic and oneshot timer support */ ret = setup_clkevents(tc, clk32k_divisor_idx); if (ret)