Re: [PATCH 34.5/36] cpuidle,omap4: Push RCU-idle into omap4_enter_lowpower()
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- To: Tony Lindgren <tony@xxxxxxxxxxx>
- Subject: Re: [PATCH 34.5/36] cpuidle,omap4: Push RCU-idle into omap4_enter_lowpower()
- From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- Date: Wed, 15 Jun 2022 00:12:06 +0200
- Cc: rth@xxxxxxxxxxxxxxx, ink@xxxxxxxxxxxxxxxxxxxx, mattst88@xxxxxxxxx, vgupta@xxxxxxxxxx, linux@xxxxxxxxxxxxxxx, ulli.kroll@xxxxxxxxxxxxxx, linus.walleij@xxxxxxxxxx, shawnguo@xxxxxxxxxx, Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>, kernel@xxxxxxxxxxxxxx, festevam@xxxxxxxxx, linux-imx@xxxxxxx, khilman@xxxxxxxxxx, catalin.marinas@xxxxxxx, will@xxxxxxxxxx, guoren@xxxxxxxxxx, bcain@xxxxxxxxxxx, chenhuacai@xxxxxxxxxx, kernel@xxxxxxxxxx, geert@xxxxxxxxxxxxxx, sammy@xxxxxxxxx, monstr@xxxxxxxxx, tsbogend@xxxxxxxxxxxxxxxx, dinguyen@xxxxxxxxxx, jonas@xxxxxxxxxxxx, stefan.kristiansson@xxxxxxxxxxxxx, shorne@xxxxxxxxx, James.Bottomley@xxxxxxxxxxxxxxxxxxxxx, deller@xxxxxx, mpe@xxxxxxxxxxxxxx, benh@xxxxxxxxxxxxxxxxxxx, paulus@xxxxxxxxx, paul.walmsley@xxxxxxxxxx, palmer@xxxxxxxxxxx, aou@xxxxxxxxxxxxxxxxx, hca@xxxxxxxxxxxxx, gor@xxxxxxxxxxxxx, agordeev@xxxxxxxxxxxxx, borntraeger@xxxxxxxxxxxxx, svens@xxxxxxxxxxxxx, ysato@xxxxxxxxxxxxx, dalias@xxxxxxxx, davem@xxxxxxxxxxxxx, richard@xxxxxx, anton.ivanov@xxxxxxxxxxxxxxxxxx, johannes@xxxxxxxxxxxxxxxx, tglx@xxxxxxxxxxxxx, mingo@xxxxxxxxxx, bp@xxxxxxxxx, dave.hansen@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, hpa@xxxxxxxxx, acme@xxxxxxxxxx, mark.rutland@xxxxxxx, alexander.shishkin@xxxxxxxxxxxxxxx, jolsa@xxxxxxxxxx, namhyung@xxxxxxxxxx, jgross@xxxxxxxx, srivatsa@xxxxxxxxxxxxx, amakhalov@xxxxxxxxxx, pv-drivers@xxxxxxxxxx, boris.ostrovsky@xxxxxxxxxx, chris@xxxxxxxxxx, jcmvbkbc@xxxxxxxxx, rafael@xxxxxxxxxx, lenb@xxxxxxxxxx, pavel@xxxxxx, gregkh@xxxxxxxxxxxxxxxxxxx, mturquette@xxxxxxxxxxxx, sboyd@xxxxxxxxxx, daniel.lezcano@xxxxxxxxxx, lpieralisi@xxxxxxxxxx, sudeep.holla@xxxxxxx, agross@xxxxxxxxxx, bjorn.andersson@xxxxxxxxxx, anup@xxxxxxxxxxxxxx, thierry.reding@xxxxxxxxx, jonathanh@xxxxxxxxxx, jacob.jun.pan@xxxxxxxxxxxxxxx, Arnd Bergmann <arnd@xxxxxxxx>, yury.norov@xxxxxxxxx, andriy.shevchenko@xxxxxxxxxxxxxxx, linux@xxxxxxxxxxxxxxxxxx, rostedt@xxxxxxxxxxx, pmladek@xxxxxxxx, senozhatsky@xxxxxxxxxxxx, john.ogness@xxxxxxxxxxxxx, paulmck@xxxxxxxxxx, frederic@xxxxxxxxxx, quic_neeraju@xxxxxxxxxxx, josh@xxxxxxxxxxxxxxxx, mathieu.desnoyers@xxxxxxxxxxxx, jiangshanlai@xxxxxxxxx, joel@xxxxxxxxxxxxxxxxx, juri.lelli@xxxxxxxxxx, vincent.guittot@xxxxxxxxxx, dietmar.eggemann@xxxxxxx, bsegall@xxxxxxxxxx, mgorman@xxxxxxx, bristot@xxxxxxxxxx, vschneid@xxxxxxxxxx, jpoimboe@xxxxxxxxxx, linux-alpha@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-snps-arc@xxxxxxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, linux-omap@xxxxxxxxxxxxxxx, linux-csky@xxxxxxxxxxxxxxx, linux-hexagon@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-m68k@xxxxxxxxxxxxxxx, linux-mips@xxxxxxxxxxxxxxx, openrisc@xxxxxxxxxxxxxxxxxxxx, linux-parisc@xxxxxxxxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx, linux-riscv@xxxxxxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, sparclinux@xxxxxxxxxxxxxxx, linux-um@xxxxxxxxxxxxxxxxxxx, linux-perf-users@xxxxxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-xtensa@xxxxxxxxxxxxxxxx, linux-acpi@xxxxxxxxxxxxxxx, linux-pm@xxxxxxxxxxxxxxx, linux-clk@xxxxxxxxxxxxxxx, linux-arm-msm@xxxxxxxxxxxxxxx, linux-tegra@xxxxxxxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, rcu@xxxxxxxxxxxxxxx
- In-reply-to: <Yqcv6crSNKuSWoTu@atomide.com>
- References: <20220608142723.103523089@infradead.org> <20220608144518.073801916@infradead.org> <Yqcv6crSNKuSWoTu@atomide.com>
On Mon, Jun 13, 2022 at 03:39:05PM +0300, Tony Lindgren wrote:
> OMAP4 uses full SoC suspend modes as idle states, as such it needs the
> whole power-domain and clock-domain code from the idle path.
>
> All that code is not suitable to run with RCU disabled, as such push
> RCU-idle deeper still.
>
> Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
> ---
>
> Peter here's one more for your series, looks like this is needed to avoid
> warnings similar to what you did for omap3.
Thanks Tony!
I've had a brief look at omap2_pm_idle() and do I understand it right
that something like the below patch would reduce it to a simple 'WFI'?
What do I do with the rest of that code, because I don't think this
thing has a cpuidle driver to take over, effectively turning it into
dead code.
--- a/arch/arm/mach-omap2/pm24xx.c
+++ b/arch/arm/mach-omap2/pm24xx.c
@@ -126,10 +126,20 @@ static int omap2_allow_mpu_retention(voi
return 1;
}
-static void omap2_enter_mpu_retention(void)
+static void omap2_do_wfi(void)
{
const int zero = 0;
+ /* WFI */
+ asm("mcr p15, 0, %0, c7, c0, 4" : : "r" (zero) : "memory", "cc");
+}
+
+#if 0
+/*
+ * possible cpuidle implementation between WFI and full_retention above
+ */
+static void omap2_enter_mpu_retention(void)
+{
/* The peripherals seem not to be able to wake up the MPU when
* it is in retention mode. */
if (omap2_allow_mpu_retention()) {
@@ -146,8 +157,7 @@ static void omap2_enter_mpu_retention(vo
pwrdm_set_next_pwrst(mpu_pwrdm, PWRDM_POWER_ON);
}
- /* WFI */
- asm("mcr p15, 0, %0, c7, c0, 4" : : "r" (zero) : "memory", "cc");
+ omap2_do_wfi();
pwrdm_set_next_pwrst(mpu_pwrdm, PWRDM_POWER_ON);
}
@@ -161,6 +171,7 @@ static int omap2_can_sleep(void)
return 1;
}
+#endif
static void omap2_pm_idle(void)
{
@@ -169,6 +180,7 @@ static void omap2_pm_idle(void)
if (omap_irq_pending())
return;
+#if 0
error = cpu_cluster_pm_enter();
if (error || !omap2_can_sleep()) {
omap2_enter_mpu_retention();
@@ -179,6 +191,9 @@ static void omap2_pm_idle(void)
out_cpu_cluster_pm:
cpu_cluster_pm_exit();
+#else
+ omap2_do_wfi();
+#endif
}
static void __init prcm_setup_regs(void)
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