Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752593AbdC2PB6 (ORCPT ); Wed, 29 Mar 2017 11:01:58 -0400 Received: from mail-io0-f181.google.com ([209.85.223.181]:34889 "EHLO mail-io0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751936AbdC2PBy (ORCPT ); Wed, 29 Mar 2017 11:01:54 -0400 MIME-Version: 1.0 In-Reply-To: <20170329144142.GL2123@mai> References: <20170321163122.9183-1-fu.wei@linaro.org> <20170321163122.9183-3-fu.wei@linaro.org> <20170328145814.GE2123@mai> <20170329144142.GL2123@mai> From: Fu Wei Date: Wed, 29 Mar 2017 23:01:50 +0800 Message-ID: Subject: Re: [PATCH v22 02/11] clocksource: arm_arch_timer: separate out device-tree code and remove arch_timer_detect_rate To: Daniel Lezcano Cc: "Rafael J. Wysocki" , Len Brown , Thomas Gleixner , Marc Zyngier , Mark Rutland , 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 Content-Length: 6910 Lines: 167 On 29 March 2017 at 22:41, Daniel Lezcano wrote: > On Wed, Mar 29, 2017 at 01:11:58PM +0800, Fu Wei wrote: >> Hi Daniel, >> >> On 29 March 2017 at 11:41, Fu Wei wrote: >> > Hi Daniel, >> > >> > Great thanks for your review, allow me to answer your question below: >> > >> > On 28 March 2017 at 22:58, Daniel Lezcano wrote: >> >> On Wed, Mar 22, 2017 at 12:31:13AM +0800, fu.wei@linaro.org wrote: >> >>> From: Fu Wei >> >>> >> >>> Currently, the counter frequency detection call(arch_timer_detect_rate) >> >>> includes getting the frequency from the device-tree property, the per-cpu >> >>> arch-timer and the memory-mapped (MMIO) timer interfaces. >> >>> But reading device-tree property will be needed only when system boot with >> >>> device-tree, and reading from the per-cpu arch-timer and the memory-mapped >> >>> (MMIO) timer interfaces will be needed only when the system initializes >> >>> the relevant timer. >> >>> >> >>> This patch separates out device-tree code, keep them in device-tree init >> >>> function, and removes arch_timer_detect_rate founction, then uses the >> >>> arch_timer_get_cntfrq and arch_timer_mem_get_cntfrq directly. >> >>> >> >>> Signed-off-by: Fu Wei >> >>> --- >> >>> drivers/clocksource/arm_arch_timer.c | 58 +++++++++++++++++++----------------- >> >>> 1 file changed, 30 insertions(+), 28 deletions(-) >> >>> >> >>> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c >> >>> index 843f923..29ca7d6 100644 >> >>> --- a/drivers/clocksource/arm_arch_timer.c >> >>> +++ b/drivers/clocksource/arm_arch_timer.c >> >>> @@ -560,30 +560,6 @@ static u32 arch_timer_mem_get_cntfrq(void __iomem *cntbase) >> >>> return readl_relaxed(cntbase + CNTFRQ); >> >>> } >> >>> >> >>> -static void >> >>> -arch_timer_detect_rate(void __iomem *cntbase, struct device_node *np) >> >>> -{ >> >>> - /* Who has more than one independent system counter? */ >> >>> - if (arch_timer_rate) >> >>> - return; >> >>> - >> >>> - /* >> >>> - * Try to determine the frequency from the device tree or CNTFRQ, >> >>> - * if ACPI is enabled, get the frequency from CNTFRQ ONLY. >> >>> - */ >> >>> - if (!acpi_disabled || >> >>> - of_property_read_u32(np, "clock-frequency", &arch_timer_rate)) { >> >>> - if (cntbase) >> >>> - arch_timer_rate = arch_timer_mem_get_cntfrq(cntbase); >> >>> - else >> >>> - arch_timer_rate = arch_timer_get_cntfrq(); >> >>> - } >> >>> - >> >>> - /* Check the timer frequency. */ >> >>> - if (arch_timer_rate == 0) >> >>> - pr_warn("frequency not available\n"); >> >>> -} >> >>> - >> >>> static void arch_timer_banner(unsigned type) >> >>> { >> >>> pr_info("%s%s%s timer(s) running at %lu.%02luMHz (%s%s%s).\n", >> >>> @@ -958,7 +934,17 @@ static int __init arch_timer_of_init(struct device_node *np) >> >>> for (i = ARCH_TIMER_PHYS_SECURE_PPI; i < ARCH_TIMER_MAX_TIMER_PPI; i++) >> >>> arch_timer_ppi[i] = irq_of_parse_and_map(np, i); >> >>> >> >>> - arch_timer_detect_rate(NULL, np); >> >>> + /* >> >>> + * Try to determine the frequency from the device tree, >> >>> + * if fail, get the frequency from the sysreg CNTFRQ. >> >>> + */ >> >>> + if (!arch_timer_rate && >> >> >> >> This variable is set only if "arm,armv7-timer" and "arm,armv7-timer-mem" are >> >> declared together in the DT, right ? >> >> >> >> Two declarations for a single variable ? Ignore the !arch_timer_rate. >> > >> > In this function, we try to initialize per-CPU arm arch_timer by DT. >> > this "!arch_timer_rate" is for testing that if we have got system >> > counter frequency from the memory-mapped timer. If so, we just skip >> > getting the frequency from DT or sysreg cntfrq again. >> > This variable is set only if "arm,armv7-timer-mem" is initialized >> > earlier than "arm,armv7-timer", in another word, maybe the node of >> > "arm,armv7-timer-mem" is declared earlier than "arm,armv7-timer-mem" >> > one in DT. >> > >> > we do this check is for keeping the same init logic as before in the >> > DT, try to avoid any possibility of breaking devices which boot by >> > DT. >> > >> >> >> >>> + of_property_read_u32(np, "clock-frequency", &arch_timer_rate)) >> >>> + arch_timer_rate = arch_timer_get_cntfrq(); >> >>> + if (!arch_timer_rate) { >> >>> + pr_err(FW_BUG "frequency not available.\n"); >> >>> + return -EINVAL; >> >>> + } >> >> >> >> Please, clarify this block, the conditions are unclear. >> > >> > this "!arch_timer_rate" is for verifying that if the system counter >> > frequency we just got from DT or sysreg cntfrq is valid(non-zero). >> > >> > So here, you can see I check arch_timer_rate twice, but they are for >> > different cases. >> >> I think about this several times, >> For this block, it is a little unclear, so I think this will be better: >> >> + /* >> + * Try to determine the frequency: >> + * If we have got it in arch_timer_mem_of_init, we don't need to get >> it again, skip. >> + * Otherwise, try to get the frequency from the device tree, >> + * if fail, try to get it from the sysreg CNTFRQ. >> + * Last, verify the arch_timer_rate before leaving this block. >> + */ >> + if (!arch_timer_rate) { >> + if (of_property_read_u32(np, "clock-frequency", &arch_timer_rate)) >> + arch_timer_rate = arch_timer_get_cntfrq(); >> + if (!arch_timer_rate) { >> + pr_err(FW_BUG "frequency not available.\n"); >> + return -EINVAL; >> + } >> + } > > Hi Fu Wei, > > in my previous comment, I was suggesting to remove the first arch_timer_rate > check. > > The code assumes something else initialized this variable. There is clearly a > conflict in the variable assignment. So if a node is defined twice for this > variable, then it is more sane to consider the second pass overwrites the first > one. As the DT are specifying the same rate, for -mem and !-mem, then it should > have not an impact (to be verified). So the code will be like this: + /* + * Try to determine the frequency: + * If we try to get the frequency from the device tree, + * if fail, try to get it from the sysreg CNTFRQ. + * Then verify the arch_timer_rate. + */ + if (of_property_read_u32(np, "clock-frequency", &arch_timer_rate)) + arch_timer_rate = arch_timer_get_cntfrq(); + if (!arch_timer_rate) { + pr_err(FW_BUG "frequency not available.\n"); + return -EINVAL; + } I am OK to delete the first arch_timer_rate check, If arch_timer_mem is initialized first, we just overwrite the existing rate to arch_timer rate. This makes sense to me. -- Best regards, Fu Wei Software Engineer Red Hat