From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751436AbdARE1l (ORCPT ); Tue, 17 Jan 2017 23:27:41 -0500 Received: from mail-it0-f43.google.com ([209.85.214.43]:36431 "EHLO mail-it0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751132AbdARE1j (ORCPT ); Tue, 17 Jan 2017 23:27:39 -0500 MIME-Version: 1.0 In-Reply-To: <20170116175025.GJ5908@leverpostej> References: <20161221064603.11830-1-fu.wei@linaro.org> <20161221064603.11830-7-fu.wei@linaro.org> <20170116175025.GJ5908@leverpostej> From: Fu Wei Date: Wed, 18 Jan 2017 12:27:37 +0800 Message-ID: Subject: Re: [PATCH v19 06/15] clocksource/drivers/arm_arch_timer: Rework counter frequency detection. To: Mark Rutland Cc: "Rafael J. Wysocki" , Len Brown , Daniel Lezcano , Thomas Gleixner , Marc Zyngier , Lorenzo Pieralisi , Sudeep Holla , Hanjun Guo , linux-arm-kernel@lists.infradead.org, Linaro ACPI Mailman List , Linux Kernel Mailing List , ACPI Devel Maling List , rruigrok@codeaurora.org, "Abdulhamid, Harb" , Christopher Covington , Timur Tabi , G Gregory , Al Stone , Jon Masters , Wei Huang , Arnd Bergmann , Catalin Marinas , Will Deacon , Suravee Suthikulpanit , Leo Duran , Wim Van Sebroeck , Guenter Roeck , linux-watchdog@vger.kernel.org, Tomasz Nowicki , Christoffer Dall , Julien Grall Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mark, On 17 January 2017 at 01:50, Mark Rutland wrote: > On Wed, Dec 21, 2016 at 02:45:54PM +0800, fu.wei@linaro.org wrote: >> From: Fu Wei >> >> Currently, the counter frequency detection call(arch_timer_detect_rate) >> combines all the ways to get counter frequency: device-tree property, >> system coprocessor register, MMIO timer. But in the most of use cases, >> we don't need all the ways to try: >> For example, reading device-tree property will be needed only when >> system boot with device-tree, getting frequency from MMIO timer register >> will beneeded only when we init MMIO timer. >> >> This patch separates paths to determine frequency: >> Separate out device-tree code, keep them in device-tree init function. > > Splitting these out makes sense to me. OK , will do > >> Separate out the MMIO frequency and the sysreg frequency detection call, >> and use the appropriate one for the counter. > >> Signed-off-by: Fu Wei >> Tested-by: Xiongfeng Wang >> --- >> drivers/clocksource/arm_arch_timer.c | 49 +++++++++++++++++++++++------------- >> 1 file changed, 31 insertions(+), 18 deletions(-) >> >> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c >> index c7b4482..9a1f138 100644 >> --- a/drivers/clocksource/arm_arch_timer.c >> +++ b/drivers/clocksource/arm_arch_timer.c >> @@ -488,27 +488,31 @@ static int arch_timer_starting_cpu(unsigned int cpu) >> return 0; >> } >> >> -static void >> -arch_timer_detect_rate(void __iomem *cntbase, struct device_node *np) >> +static void arch_timer_detect_rate(void) >> { >> - /* Who has more than one independent system counter? */ >> - if (arch_timer_rate) >> - return; >> + /* >> + * Try to get the timer frequency from >> + * cntfrq_el0(system coprocessor register). >> + */ >> + if (!arch_timer_rate) >> + arch_timer_rate = arch_timer_get_cntfrq(); >> + >> + /* Check the timer frequency. */ >> + if (!arch_timer_rate) >> + pr_warn("frequency not available\n"); >> +} >> >> +static void arch_timer_mem_detect_rate(void __iomem *cntbase) >> +{ >> /* >> - * Try to determine the frequency from the device tree or CNTFRQ, >> - * if ACPI is enabled, get the frequency from CNTFRQ ONLY. >> + * Try to determine the frequency from >> + * CNTFRQ in memory-mapped timer. >> */ >> - if (!acpi_disabled || >> - of_property_read_u32(np, "clock-frequency", &arch_timer_rate)) { >> - if (cntbase) >> - arch_timer_rate = readl_relaxed(cntbase + CNTFRQ); >> - else >> - arch_timer_rate = arch_timer_get_cntfrq(); >> - } >> + if (!arch_timer_rate) >> + arch_timer_rate = readl_relaxed(cntbase + CNTFRQ); >> >> /* Check the timer frequency. */ >> - if (arch_timer_rate == 0) >> + if (!arch_timer_rate) I think you mean this one, this is for keeping consistency with arch_timer_detect_rate. >> pr_warn("frequency not available\n"); >> } > > There's a subtle change in behaviour here. Previously for ACPI we'd only > ever use the sysreg CNTFRQ value for arch_timer_rate, whereas now we > might use the MMIO timer rate. Maybe that's not a big deal, but I will > need to think. > > Generally, the logic to determine the rate is fairly gnarly regardless. > > It would be nice if we could split the MMIO and sysreg rates entirely, Yes, I am doing this way, For sysreg rates, static void arch_timer_detect_rate(void) { /* * Try to get the timer frequency from * cntfrq_el0(system coprocessor register). */ if (!arch_timer_rate) arch_timer_rate = arch_timer_get_cntfrq(); /* Check the timer frequency. */ if (!arch_timer_rate) pr_warn("frequency not available\n"); } For MMIO timer, static void arch_timer_mem_detect_rate(void __iomem *cntbase) { /* * Try to determine the frequency from * CNTFRQ in memory-mapped timer. */ if (!arch_timer_rate) arch_timer_rate = readl_relaxed(cntbase + CNTFRQ); /* Check the timer frequency. */ if (!arch_timer_rate) pr_warn("frequency not available\n"); } in arch_time_*_init, only call arch_timer_detect_rate, in arch_timer_mem_init, only call arch_timer_mem_detect_rate. But you are right, this is fairly gnarly regardless. > and kill the implicit relationship between the two, or at least make one > canonical and warn if the two differ. So I think maybe we can do this: static void __arch_timer_determine_rate(u32 rate) { /* Check the timer frequency. */ if (!arch_timer_rate) if (rate) arch_timer_rate = rate; else pr_warn("frequency not available\n"); else if (arch_timer_rate != rate) pr_warn("got different frequency, keep original.\n"); } static void arch_timer_detect_rate(void) { /* * Try to get the timer frequency from * cntfrq_el0(system coprocessor register). */ __arch_timer_determine_rate(arch_timer_get_cntfrq()); } static void arch_timer_mem_detect_rate(void __iomem *cntbase) { /* * Try to get the timer frequency from * CNTFRQ in the MMIO timer. */ __arch_timer_determine_rate(readl_relaxed(cntbase + CNTFRQ)); } any thought? > > Thanks, > Mark. -- Best regards, Fu Wei Software Engineer Red Hat