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Date: Wed, 29 Mar 2017 13:11:58 +0800 From: Fu Wei <fu.wei@...aro.org> To: Daniel Lezcano <daniel.lezcano@...aro.org> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Len Brown <lenb@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Marc Zyngier <marc.zyngier@....com>, Mark Rutland <mark.rutland@....com>, Lorenzo Pieralisi <lorenzo.pieralisi@....com>, Sudeep Holla <sudeep.holla@....com>, Hanjun Guo <hanjun.guo@...aro.org>, linux-arm-kernel@...ts.infradead.org, Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, ACPI Devel Maling List <linux-acpi@...r.kernel.org>, rruigrok@...eaurora.org, "Abdulhamid, Harb" <harba@...eaurora.org>, Christopher Covington <cov@...eaurora.org>, Timur Tabi <timur@...eaurora.org>, G Gregory <graeme.gregory@...aro.org>, Al Stone <al.stone@...aro.org>, Jon Masters <jcm@...hat.com>, Wei Huang <wei@...hat.com>, Arnd Bergmann <arnd@...db.de>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>, Leo Duran <leo.duran@....com>, Wim Van Sebroeck <wim@...ana.be>, Guenter Roeck <linux@...ck-us.net>, linux-watchdog@...r.kernel.org, Tomasz Nowicki <tn@...ihalf.com>, Christoffer Dall <christoffer.dall@...aro.org>, Julien Grall <julien.grall@....com> Subject: Re: [PATCH v22 02/11] clocksource: arm_arch_timer: separate out device-tree code and remove arch_timer_detect_rate Hi Daniel, On 29 March 2017 at 11:41, Fu Wei <fu.wei@...aro.org> wrote: > Hi Daniel, > > Great thanks for your review, allow me to answer your question below: > > On 28 March 2017 at 22:58, Daniel Lezcano <daniel.lezcano@...aro.org> wrote: >> On Wed, Mar 22, 2017 at 12:31:13AM +0800, fu.wei@...aro.org wrote: >>> From: Fu Wei <fu.wei@...aro.org> >>> >>> 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 <fu.wei@...aro.org> >>> --- >>> 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; + } + } > >> >>> >>> arch_timer_c3stop = !of_property_read_bool(np, "always-on"); >>> >>> @@ -1069,7 +1055,19 @@ static int __init arch_timer_mem_init(struct device_node *np) >>> goto out; >>> } >>> >>> - arch_timer_detect_rate(base, np); >>> + /* >>> + * Try to determine the frequency from the device tree, >>> + * if fail, get the frequency from the CNTFRQ reg of MMIO timer. >>> + */ >>> + if (!arch_timer_rate && >>> + of_property_read_u32(np, "clock-frequency", &arch_timer_rate)) >>> + arch_timer_rate = arch_timer_mem_get_cntfrq(base); >>> + if (!arch_timer_rate) { >>> + pr_err(FW_BUG "MMIO frequency not available.\n"); >>> + ret = -EINVAL; >>> + goto out; >>> + } >>> + >>> ret = arch_timer_mem_register(base, irq); >>> if (ret) >>> goto out; >>> @@ -1130,8 +1128,12 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table) >>> map_generic_timer_interrupt(gtdt->non_secure_el2_interrupt, >>> gtdt->non_secure_el2_flags); >>> >>> - /* Get the frequency from CNTFRQ */ >>> - arch_timer_detect_rate(NULL, NULL); >>> + /* Get the frequency from the sysreg CNTFRQ */ >>> + arch_timer_rate = arch_timer_get_cntfrq(); >>> + if (!arch_timer_rate) { >>> + pr_err(FW_BUG "frequency not available.\n"); >>> + return -EINVAL; >>> + } >>> >>> arch_timer_uses_ppi = arch_timer_select_ppi(); >>> if (!arch_timer_ppi[arch_timer_uses_ppi]) { >>> -- >>> 2.9.3 >>> >> >> -- >> >> <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs >> >> Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | >> <http://twitter.com/#!/linaroorg> Twitter | >> <http://www.linaro.org/linaro-blog/> Blog > > > > -- > Best regards, > > Fu Wei > Software Engineer > Red Hat -- Best regards, Fu Wei Software Engineer Red Hat
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