linux-kernel - Re: [PATCH v14 5/9] clocksource/drivers/arm_arch

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Date:   Thu, 20 Oct 2016 17:58:17 +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 v14 5/9] clocksource/drivers/arm_arch_timer: Simplify
 ACPI support code.

On Thu, Sep 29, 2016 at 02:17:13AM +0800, fu.wei@...aro.org wrote:
> From: Fu Wei <fu.wei@...aro.org>
> 
> The patch update arm_arch_timer driver to use the function
> provided by the new GTDT driver of ACPI.
> By this way, arm_arch_timer.c can be simplified, and separate
> all the ACPI GTDT knowledge from this timer driver.
> 
> Signed-off-by: Fu Wei <fu.wei@...aro.org>
> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>

This generally looks fine, but:

> +	arch_timer_ppi[PHYS_SECURE_PPI] = acpi_gtdt_map_ppi(PHYS_SECURE_PPI);

As mentioned on the prior patch, I think we shouldn't bother parsing the
secure interrupt, given the problem with the GSIV, and the fact that we
shouldn't need it in Linux.

> +	arch_timer_ppi[PHYS_NONSECURE_PPI] = acpi_gtdt_map_ppi(PHYS_NONSECURE_PPI);
> +	arch_timer_ppi[VIRT_PPI] = acpi_gtdt_map_ppi(VIRT_PPI);
> +	arch_timer_ppi[HYP_PPI] = acpi_gtdt_map_ppi(HYP_PPI);
> +	/* Always-on capability */
> +	arch_timer_c3stop = acpi_gtdt_c3stop();

... I think we should check the flag on the relevant interrupt, though
that's worth clarifying.

>  
> -	/* Always-on capability */
> -	arch_timer_c3stop = !(gtdt->non_secure_el1_flags & ACPI_GTDT_ALWAYS_ON);
> +	if (timer_count < 0)
> +		pr_err("Failed to get platform timer info.\n");

Why don't we log this in the code that would try to initialise the MMIO
timer? We can still fail after this.

Thanks,
Mark.