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Message-ID: <570E7263.8070108@arm.com>
Date: Wed, 13 Apr 2016 17:22:59 +0100
From: Marc Zyngier <marc.zyngier@....com>
To: Vineet Gupta <Vineet.Gupta1@...opsys.com>,
Thomas Gleixner <tglx@...utronix.de>,
Jason Cooper <jason@...edaemon.net>,
Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
Noam Camus <noamc@...hip.com>
Subject: Re: [PATCH v4 2/5] ARC: clocksource: DT based probe
On 13/04/16 12:40, Vineet Gupta wrote:
> - Remove explicit clocksource setup and let it be done by OF framework
> by defining CLOCKSOURCE_OF_DECLARE() for various timers
>
> - This allows multiple clocksources to be potentially registered
> simultaneouly: previously we could only do one - as all of them had
> same arc_counter_setup() routine for registration
>
> - Setup routines also ensure that the underlying timer actually exists.
>
> - Remove some of the panic() calls if underlying timer is NOT detected as
> fallback clocksource might still be available
> 1. If GRFC doesn't exist, jiffies clocksource gets registered anyways
> 2. if RTC doesn't exist, TIMER1 can take over (as it is always
> present)
>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
> ---
> arch/arc/kernel/mcip.c | 4 +-
> arch/arc/kernel/setup.c | 3 --
> arch/arc/kernel/time.c | 124 +++++++++++++++++++++++++++---------------------
> 3 files changed, 72 insertions(+), 59 deletions(-)
>
> diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c
> index c41c364b926c..262d9c3771e6 100644
> --- a/arch/arc/kernel/mcip.c
> +++ b/arch/arc/kernel/mcip.c
> @@ -116,15 +116,13 @@ static void mcip_probe_n_setup(void)
> IS_AVAIL1(mp.dbg, "DEBUG "),
> IS_AVAIL1(mp.gfrc, "GFRC"));
>
> + cpuinfo_arc700[0].extn.gfrc = mp.gfrc;
> idu_detected = mp.idu;
>
> if (mp.dbg) {
> __mcip_cmd_data(CMD_DEBUG_SET_SELECT, 0, 0xf);
> __mcip_cmd_data(CMD_DEBUG_SET_MASK, 0xf, 0xf);
> }
> -
> - if (IS_ENABLED(CONFIG_ARC_HAS_GFRC) && !mp.gfrc)
> - panic("kernel trying to use non-existent GFRC\n");
> }
>
> struct plat_smp_ops plat_smp_ops = {
> diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
> index 507ec523112a..91f79fa447bc 100644
> --- a/arch/arc/kernel/setup.c
> +++ b/arch/arc/kernel/setup.c
> @@ -313,9 +313,6 @@ static void arc_chk_core_config(void)
> if (!cpu->extn.timer1)
> panic("Timer1 is not present!\n");
>
> - if (IS_ENABLED(CONFIG_ARC_HAS_RTC) && !cpu->extn.rtc)
> - panic("RTC is not present\n");
> -
> #ifdef CONFIG_ARC_HAS_DCCM
> /*
> * DCCM can be arbit placed in hardware.
> diff --git a/arch/arc/kernel/time.c b/arch/arc/kernel/time.c
> index 693545df9827..72f023440739 100644
> --- a/arch/arc/kernel/time.c
> +++ b/arch/arc/kernel/time.c
> @@ -77,12 +77,7 @@ static void noinline arc_get_timer_clk(struct device_node *node)
>
> #ifdef CONFIG_ARC_HAS_GFRC
>
> -static int arc_counter_setup(void)
> -{
> - return 1;
> -}
> -
> -static cycle_t arc_counter_read(struct clocksource *cs)
> +static cycle_t arc_read_gfrc(struct clocksource *cs)
> {
> unsigned long flags;
> union {
> @@ -107,15 +102,28 @@ static cycle_t arc_counter_read(struct clocksource *cs)
> return stamp.full;
> }
>
> -static struct clocksource arc_counter = {
> +static struct clocksource arc_counter_gfrc = {
> .name = "ARConnect GFRC",
> .rating = 400,
> - .read = arc_counter_read,
> + .read = arc_read_gfrc,
> .mask = CLOCKSOURCE_MASK(64),
> .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> };
>
> -#else
> +static void __init arc_cs_setup_gfrc(struct device_node *node)
> +{
> + int exists = cpuinfo_arc700[0].extn.gfrc;
> +
> + if (WARN(!exists, "Global-64-bit-Ctr clocksource not detected"))
> + return;
> +
> + arc_get_timer_clk(node);
> +
> + clocksource_register_hz(&arc_counter_gfrc, arc_timer_freq);
> +}
> +CLOCKSOURCE_OF_DECLARE(arc_gfrc, "snps,archs-timer-gfrc", arc_cs_setup_gfrc);
> +
> +#endif
>
> #ifdef CONFIG_ARC_HAS_RTC
>
> @@ -123,15 +131,7 @@ static struct clocksource arc_counter = {
> #define AUX_RTC_LOW 0x104
> #define AUX_RTC_HIGH 0x105
>
> -int arc_counter_setup(void)
> -{
> - write_aux_reg(AUX_RTC_CTRL, 1);
> -
> - /* Not usable in SMP */
> - return !IS_ENABLED(CONFIG_SMP);
> -}
> -
> -static cycle_t arc_counter_read(struct clocksource *cs)
> +static cycle_t arc_read_rtc(struct clocksource *cs)
> {
> unsigned long status;
> union {
> @@ -155,44 +155,66 @@ static cycle_t arc_counter_read(struct clocksource *cs)
> return stamp.full;
> }
>
> -static struct clocksource arc_counter = {
> +static struct clocksource arc_counter_rtc = {
> .name = "ARCv2 RTC",
> .rating = 350,
> - .read = arc_counter_read,
> + .read = arc_read_rtc,
> .mask = CLOCKSOURCE_MASK(64),
> .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> };
>
> -#else /* !CONFIG_ARC_HAS_RTC */
> -
> -/*
> - * set 32bit TIMER1 to keep counting monotonically and wraparound
> - */
> -int arc_counter_setup(void)
> +static void __init arc_cs_setup_rtc(struct device_node *node)
> {
> - write_aux_reg(ARC_REG_TIMER1_LIMIT, ARC_TIMER_MAX);
> - write_aux_reg(ARC_REG_TIMER1_CNT, 0);
> - write_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
> + int exists = cpuinfo_arc700[smp_processor_id()].extn.rtc;
> +
> + if (WARN(!exists, "Local-64-bit-Ctr clocksource not detected"))
> + return;
> +
> + /* Local to CPU hence not usable in SMP */
> + if (WARN(IS_ENABLED(CONFIG_SMP), "Local-64-bit-Ctr not usable in SMP"))
> + return;
Sorry if this outlines my lack of understanding of the ARC architecture,
but what makes per-cpu timer unsuitable for SMP? I'd have thought that
it was actually what you wanted...
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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