linux-kernel - Re: [RESEND PATCH v4 5/5] clocksource: add memory-mapped timer support in arm_arch

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Message-ID: <alpine.DEB.2.11.1603181031280.3978@nanos>
Date:	Fri, 18 Mar 2016 10:32:48 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Fu Wei <fu.wei@...aro.org>
cc:	rjw@...ysocki.net, lenb@...nel.org, daniel.lezcano@...aro.org,
	marc.zyngier@....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,
	wim@...ana.be, catalin.marinas@....com, will.deacon@....com,
	Suravee.Suthikulpanit@....com, leo.duran@....com
Subject: Re: [RESEND PATCH v4 5/5] clocksource: add memory-mapped timer
 support in arm_arch_timer.c

On Fri, 18 Mar 2016, fu.wei@...aro.org wrote:
> +static u32 __init arch_timer_mem_cnttidr(struct acpi_gtdt_timer_block *gt_block)
> +{
> +	phys_addr_t cntctlbase_phy;
> +	void __iomem *cntctlbase;
> +	u32 cnttidr;
> +
> +	cntctlbase_phy = (phys_addr_t)gtdt_gt_cntctlbase(gt_block);
> +	if (!cntctlbase_phy) {
> +		pr_err("Can't find CNTCTLBase.\n");
> +		return 0;
> +	}
> +
> +	/*
> +	 * According to ARMv8 Architecture Reference Manual(ARM),
> +	 * the size of CNTCTLBase frame of memory-mapped timer
> +	 * is SZ_4K(Offset 0x000 – 0xFFF).
> +	 */
> +	cntctlbase = ioremap(cntctlbase_phy, SZ_4K);
> +	if (!cntctlbase) {
> +		pr_err("Can't map CNTCTLBase\n");
> +		return 0;
> +	}

Why are you continuing when you can't find a base address or the remap fails?

> +	/*
> +	 * Get Generic Timer Counter-timer Timer ID Register
> +	 * for Virtual Timer Capability info
> +	 */
> +	cnttidr = arch_timer_mem_cnttidr(gt_block);

Thanks,

	tglx