From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752267AbdC2Olx (ORCPT ); Wed, 29 Mar 2017 10:41:53 -0400 Received: from mail-wr0-f175.google.com ([209.85.128.175]:33485 "EHLO mail-wr0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751583AbdC2Olu (ORCPT ); Wed, 29 Mar 2017 10:41:50 -0400 Date: Wed, 29 Mar 2017 16:41:42 +0200 From: Daniel Lezcano To: Fu Wei 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 Subject: Re: [PATCH v22 02/11] clocksource: arm_arch_timer: separate out device-tree code and remove arch_timer_detect_rate Message-ID: <20170329144142.GL2123@mai> References: <20170321163122.9183-1-fu.wei@linaro.org> <20170321163122.9183-3-fu.wei@linaro.org> <20170328145814.GE2123@mai> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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).