linux-kernel - Re: [PATCH v23 06/11] clocksource: arm_arch

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Date:   Wed, 5 Apr 2017 19:42:30 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     fu.wei@...aro.org
Cc:     rjw@...ysocki.net, lenb@...nel.org, daniel.lezcano@...aro.org,
        tglx@...utronix.de, marc.zyngier@....com,
        lorenzo.pieralisi@....com, sudeep.holla@....com,
        hanjun.guo@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linaro-acpi@...ts.linaro.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, rruigrok@...eaurora.org,
        harba@...eaurora.org, cov@...eaurora.org, timur@...eaurora.org,
        graeme.gregory@...aro.org, al.stone@...aro.org, jcm@...hat.com,
        wei@...hat.com, arnd@...db.de, catalin.marinas@....com,
        will.deacon@....com, Suravee.Suthikulpanit@....com,
        leo.duran@....com, wim@...ana.be, linux@...ck-us.net,
        linux-watchdog@...r.kernel.org, tn@...ihalf.com,
        christoffer.dall@...aro.org, julien.grall@....com
Subject: Re: [PATCH v23 06/11] clocksource: arm_arch_timer: refactor MMIO
 timer probing.

On Sat, Apr 01, 2017 at 01:51:00AM +0800, fu.wei@...aro.org wrote:
> +	arch_timer_mem_freq = arch_timer_mem_get_cntfrq(base);
> +	if (!arch_timer_rate && arch_timer_mem_freq) {
> +		arch_timer_rate = arch_timer_mem_freq;
> +	} else if (!arch_timer_rate || arch_timer_rate != arch_timer_mem_freq) {
> +		pr_err(FW_BUG "invalid MMIO frequency.\n");
> +		iounmap(base);
> +		return -EINVAL;
> +	}

I thought I had previously mentioned that this last check has the
potential to break DT systems, which may be inadvertently relying on the
probe order.

I agree we must do this check for ACPI, but I think that for DT it needs
to be relaxed.

I'm happy to rework that locally, if you can address my comments on
patch 9.

Thanks,
Mark.