From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: Re: [PATCH 5/9] clocksource: tegra: Enable ARM arch_timer with TSC Date: Thu, 20 Dec 2012 12:05:45 +0000 Message-ID: <50D2FF19.4060600@arm.com> References: <1355996654-6579-1-git-send-email-hdoyu@nvidia.com><1355996654-6579-6-git-send-email-hdoyu@nvidia.com><50D2EFFB.8030702@arm.com> <20121220.135758.1347753620353343245.hdoyu@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <20121220.135758.1347753620353343245.hdoyu@nvidia.com> Sender: linux-doc-owner@vger.kernel.org To: Hiroshi Doyu Cc: "linux-tegra@vger.kernel.org" , "andrew@lunn.ch" , "linux@arm.linux.org.uk" , "jason@lakedaemon.net" , "johnstul@us.ibm.com" , "devicetree-discuss@lists.ozlabs.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "rob.herring@calxeda.com" , "tglx@linutronix.de" , "linux-arm-kernel@lists.infradead.org" List-Id: devicetree@vger.kernel.org On 20/12/12 11:57, Hiroshi Doyu wrote: > Marc Zyngier wrote @ Thu, 20 Dec 2012 12:01:15 +0100: > >> On 20/12/12 09:44, Hiroshi Doyu wrote: >>> Add platform enabler for ARM arch_timer(TSC). TSC is more fine grained >>> timer than TMR0. If it's available, it will be used for clock source >>> and sched_clock. Otherwise, TMR0 is used. In any case TMR0 is >>> necessary for clock event. >>> >>> Signed-off-by: Hiroshi Doyu >>> --- >>> .../bindings/arm/tegra/nvidia,tegra114-tsc.txt | 11 ++++ >>> drivers/clocksource/tegra20_timer.c | 64 +++++++++++++++++++- >>> 2 files changed, 74 insertions(+), 1 deletion(-) >>> create mode 100644 Documentation/devicetree/bindings/arm/tegra/nvidia,tegra114-tsc.txt >>> >>> diff --git a/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra114-tsc.txt b/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra114-tsc.txt >>> new file mode 100644 >>> index 0000000..9de936a >>> --- /dev/null >>> +++ b/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra114-tsc.txt >>> @@ -0,0 +1,11 @@ >>> +NVIDIA Tegra Timer Stamp Counter(TSC) >>> + >>> +Required properties: >>> +- compatible : "nvidia,tegra114-tsc >>> +- reg : Should contain 1 register ranges(address and length) >>> + >>> +Example: >>> + tsc { >>> + compatible = "nvidia,tegra114-tsc"; >>> + reg = <0x700f0000 0x20000>; >>> + }; >>> diff --git a/drivers/clocksource/tegra20_timer.c b/drivers/clocksource/tegra20_timer.c >>> index 1d25de8..285a6f1 100644 >>> --- a/drivers/clocksource/tegra20_timer.c >>> +++ b/drivers/clocksource/tegra20_timer.c >>> @@ -30,6 +30,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> >>> #define RTC_SECONDS 0x08 >>> #define RTC_SHADOW_SECONDS 0x0c >>> @@ -271,10 +272,71 @@ static void __init tegra20_init_tmr(void) >>> clockevents_register_device(&tegra_clockevent); >>> } >>> >>> +#define TSC_CNTCR 0 /* TSC control registers */ >>> +#define TSC_CNTCR_ENABLE (1 << 0) /* Enable */ >>> +#define TSC_CNTCR_HDBG (1 << 1) /* Halt on debug */ >>> + >>> +#define TSC_CNTCV0 0x8 /* TSC counter (LSW) */ >>> +#define TSC_CNTCV1 0xc /* TSC counter (MSW) */ >>> +#define TSC_CNTFID0 0x20 /* TSC freq id 0 */ >>> + >>> +static const struct of_device_id tegra_tsc_match[] __initconst = { >>> + { .compatible = "nvidia,tegra114-tsc" }, >>> + {} >>> +}; >>> + >>> +static int tegra_arch_timer_init(void) >>> +{ >>> + int err; >>> + struct device_node *np; >>> + struct clk *clk; >>> + void __iomem *tsc_base; >>> + u32 freq, val; >>> + >>> + np = of_find_matching_node(NULL, tegra_tsc_match); >>> + if (!np) >>> + return -ENODEV; >>> + >>> + tsc_base = of_iomap(np, 0); >>> + if (!tsc_base) >>> + return -ENODEV; >>> + >>> + clk = clk_get_sys("clk_m", NULL); >>> + if (IS_ERR(clk)) { >>> + freq = 12000000; >>> + pr_warn("Unable to get timer clock. Assuming 12Mhz input clock.\n"); >>> + } else { >>> + freq = clk_get_rate(clk); >>> + clk_put(clk); >>> + } >>> + writel_relaxed(freq, tsc_base + TSC_CNTFID0); >>> + >>> + /* CNTFRQ */ >>> + asm("mcr p15, 0, %0, c14, c0, 0\n" : : "r" (freq)); >>> + asm("mrc p15, 0, %0, c14, c0, 0\n" : "=r" (val)); >>> + BUG_ON(val != freq); >> >> This is scary. CNTFRQ is only writable from secure mode, and will >> explode in any other situation. >> >> Also, writing to CNTFRQ doesn't change the timer frequency! This is just >> a way for secure mode to tell the rest of the world the frequency the >> timer is ticking at. Unless you've wired the input clock to be able to >> change the frequency? > > ATM, our upstream kernel is expected in secure mode. This situation > may be changed later, though.... I appreciate this. But I expect this kernel to be also used on the non-secure side if someone tried to run KVM with it. And this would go bang right away. M. -- Jazz is not dead. It just smells funny...