linux-kernel - Re: [PATCH 1/9] ARC: timer: gfrc, rtc: Read BCR to detect whether hardware exists ...

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Date:   Thu, 3 Nov 2016 18:00:56 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Vineet Gupta <Vineet.Gupta1@...opsys.com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        linux-snps-arc@...ts.infradead.org,
        Noam Camus <noamca@...lanox.com>, Alexey.Brodkin@...opsys.com
Subject: Re: [PATCH 1/9] ARC: timer: gfrc, rtc: Read BCR to detect whether
 hardware exists ...

On Mon, Oct 31, 2016 at 03:48:08PM -0700, Vineet Gupta wrote:
> ... don't rely on cpuinfo populated in arc boot code. This paves wat for
> moving this code in drivers/clocksource/
> 
> Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
> ---
>  arch/arc/kernel/time.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arc/kernel/time.c b/arch/arc/kernel/time.c
> index f927b8dc6edd..a2db010cde18 100644
> --- a/arch/arc/kernel/time.c
> +++ b/arch/arc/kernel/time.c
> @@ -118,10 +118,11 @@ static struct clocksource arc_counter_gfrc = {
>  
>  static int __init arc_cs_setup_gfrc(struct device_node *node)
>  {
> -	int exists = cpuinfo_arc700[0].extn.gfrc;
> +	struct mcip_bcr mp;
>  	int ret;
>  
> -	if (WARN(!exists, "Global-64-bit-Ctr clocksource not detected"))
> +	READ_BCR(ARC_REG_MCIP_BCR, mp);
> +	if (WARN(!mp.gfrc, "Global-64-bit-Ctr clocksource not detected"))

Take the opportunity to replace this WARN by a pr_err.

>  		return -ENXIO;
>  
>  	ret = arc_get_timer_clk(node);
> @@ -174,10 +175,11 @@ static struct clocksource arc_counter_rtc = {
>  
>  static int __init arc_cs_setup_rtc(struct device_node *node)
>  {
> -	int exists = cpuinfo_arc700[smp_processor_id()].extn.rtc;
> +	struct bcr_timer timer;
>  	int ret;
>  
> -	if (WARN(!exists, "Local-64-bit-Ctr clocksource not detected"))
> +	READ_BCR(ARC_REG_TIMERS_BCR, timer);
> +	if (WARN(!timer.rtc, "Local-64-bit-Ctr clocksource not detected"))
>  		return -ENXIO;o

Ditto and                    ^^

So the READ_BCR() is only there to check the timer is physically present ?

>  	/* Local to CPU hence not usable in SMP */
> -- 
> 2.7.4
>