[PATCH V2 2/6] ARM: tegra20: cpuidle: add powered-down state for secondary CPU
From: Lorenzo Pieralisi <hidden>
Date: 2012-12-05 10:50:15
Also in:
linux-tegra
On Wed, Dec 05, 2012 at 10:01:49AM +0000, Joseph Lo wrote:
quoted hunk ↗ jump to hunk
The powered-down state of Tegra20 requires power gating both CPU cores. When the secondary CPU requests to enter powered-down state, it saves its own contexts and then enters WFI. The Tegra20 had a limition to power down both CPU cores. The secondary CPU must waits for CPU0 in powered-down state too. If the secondary CPU be woken up before CPU0 entering powered-down state, then it needs to restore its CPU states and waits for next chance. Be aware of that, you may see the legacy power state "LP2" in the code which is exactly the same meaning of "CPU power down". Based on the work by: Colin Cross [off-list ref] Gary King [off-list ref] Signed-off-by: Joseph Lo <redacted> --- V2: * no change --- arch/arm/mach-tegra/cpuidle-tegra20.c | 84 +++++++++++++++++++ arch/arm/mach-tegra/pm.c | 2 + arch/arm/mach-tegra/sleep-tegra20.S | 145 +++++++++++++++++++++++++++++++++ arch/arm/mach-tegra/sleep.h | 23 +++++ 4 files changed, 254 insertions(+), 0 deletions(-)diff --git a/arch/arm/mach-tegra/cpuidle-tegra20.c b/arch/arm/mach-tegra/cpuidle-tegra20.c index d32e8b0..9d59a46 100644 --- a/arch/arm/mach-tegra/cpuidle-tegra20.c +++ b/arch/arm/mach-tegra/cpuidle-tegra20.c@@ -22,21 +22,105 @@ #include <linux/kernel.h> #include <linux/module.h> #include <linux/cpuidle.h> +#include <linux/cpu_pm.h> +#include <linux/clockchips.h> #include <asm/cpuidle.h> +#include <asm/proc-fns.h> +#include <asm/suspend.h> +#include <asm/smp_plat.h> + +#include "pm.h" +#include "sleep.h" + +#ifdef CONFIG_PM_SLEEP +static int tegra20_idle_lp2(struct cpuidle_device *dev, + struct cpuidle_driver *drv, + int index); +#endif static struct cpuidle_driver tegra_idle_driver = { .name = "tegra_idle", .owner = THIS_MODULE, .en_core_tk_irqen = 1, +#ifdef CONFIG_PM_SLEEP + .state_count = 2, +#else .state_count = 1, +#endif
These hardcoded values are not nice.
.states = {
[0] = ARM_CPUIDLE_WFI_STATE_PWR(600),
+#ifdef CONFIG_PM_SLEEP
+ [1] = {
+ .enter = tegra20_idle_lp2,
+ .exit_latency = 5000,
+ .target_residency = 10000,
+ .power_usage = 0,
+ .flags = CPUIDLE_FLAG_TIME_VALID,
+ .name = "powered-down",
+ .desc = "CPU power gated",
+ },
+#endif
},
};
static DEFINE_PER_CPU(struct cpuidle_device, tegra_idle_device);
+#ifdef CONFIG_PM_SLEEP
+#ifdef CONFIG_SMP
+static bool tegra20_idle_enter_lp2_cpu_1(struct cpuidle_device *dev,
+ struct cpuidle_driver *drv,
+ int index)
+{
+ clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu);
+
+ smp_wmb();Can you explain to me the need for this barrier ?
quoted hunk ↗ jump to hunk
+ + cpu_suspend(0, tegra20_sleep_cpu_secondary_finish); + + tegra20_cpu_clear_resettable(); + + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu); + + return true; +} +#else +static inline bool tegra20_idle_enter_lp2_cpu_1(struct cpuidle_device *dev, + struct cpuidle_driver *drv, + int index) +{ + return true; +} +#endif + +static int __cpuinit tegra20_idle_lp2(struct cpuidle_device *dev, + struct cpuidle_driver *drv, + int index) +{ + u32 cpu = is_smp() ? cpu_logical_map(dev->cpu) : dev->cpu; + bool entered_lp2 = false; + + local_fiq_disable(); + + tegra_set_cpu_in_lp2(cpu); + cpu_pm_enter(); + + if (cpu == 0) + cpu_do_idle(); + else + entered_lp2 = tegra20_idle_enter_lp2_cpu_1(dev, drv, index); + + cpu_pm_exit(); + tegra_clear_cpu_in_lp2(cpu); + + local_fiq_enable(); + + smp_rmb(); + + return (entered_lp2) ? index : 0; +} +#endif + int __init tegra20_cpuidle_init(void) { int ret;diff --git a/arch/arm/mach-tegra/pm.c b/arch/arm/mach-tegra/pm.c index 1b11707..db72ea9 100644 --- a/arch/arm/mach-tegra/pm.c +++ b/arch/arm/mach-tegra/pm.c@@ -173,6 +173,8 @@ bool __cpuinit tegra_set_cpu_in_lp2(int phy_cpu_id) if ((phy_cpu_id == 0) && cpumask_equal(cpu_lp2_mask, cpu_online_mask)) last_cpu = true; + else if (phy_cpu_id == 1) + tegra20_cpu_set_resettable_soon(); spin_unlock(&tegra_lp2_lock); return last_cpu;diff --git a/arch/arm/mach-tegra/sleep-tegra20.S b/arch/arm/mach-tegra/sleep-tegra20.S index 72ce709..dfb2be5 100644 --- a/arch/arm/mach-tegra/sleep-tegra20.S +++ b/arch/arm/mach-tegra/sleep-tegra20.S@@ -21,6 +21,8 @@ #include <linux/linkage.h> #include <asm/assembler.h> +#include <asm/proc-fns.h> +#include <asm/cp15.h> #include "sleep.h" #include "flowctrl.h"@@ -78,3 +80,146 @@ ENTRY(tegra20_cpu_shutdown) mov pc, lr ENDPROC(tegra20_cpu_shutdown) #endif + +#ifdef CONFIG_PM_SLEEP +/* + * tegra_pen_lock + * + * spinlock implementation with no atomic test-and-set and no coherence + * using Peterson's algorithm on strongly-ordered registers + * used to synchronize a cpu waking up from wfi with entering lp2 on idle + * + * SCRATCH37 = r1 = !turn (inverted from Peterson's algorithm) + * on cpu 0: + * SCRATCH38 = r2 = flag[0] + * SCRATCH39 = r3 = flag[1] + * on cpu1: + * SCRATCH39 = r2 = flag[1] + * SCRATCH38 = r3 = flag[0] + * + * must be called with MMU on + * corrupts r0-r3, r12 + */ +ENTRY(tegra_pen_lock) + mov32 r3, TEGRA_PMC_VIRT + cpu_id r0 + add r1, r3, #PMC_SCRATCH37 + cmp r0, #0 + addeq r2, r3, #PMC_SCRATCH38 + addeq r3, r3, #PMC_SCRATCH39 + addne r2, r3, #PMC_SCRATCH39 + addne r3, r3, #PMC_SCRATCH38 + + mov r12, #1 + str r12, [r2] @ flag[cpu] = 1 + dsb + str r12, [r1] @ !turn = cpu +1: dsb + ldr r12, [r3] + cmp r12, #1 @ flag[!cpu] == 1? + ldreq r12, [r1] + cmpeq r12, r0 @ !turn == cpu? + beq 1b @ while !turn == cpu && flag[!cpu] == 1 + + mov pc, lr @ locked +ENDPROC(tegra_pen_lock) + +ENTRY(tegra_pen_unlock) + dsb + mov32 r3, TEGRA_PMC_VIRT + cpu_id r0 + cmp r0, #0 + addeq r2, r3, #PMC_SCRATCH38 + addne r2, r3, #PMC_SCRATCH39 + mov r12, #0 + str r12, [r2] + mov pc, lr +ENDPROC(tegra_pen_unlock)
There is an ongoing work to make this locking scheme for MMU/coherency off paths ARM generic, and we do not want to merge yet another platform specific locking mechanism. I will point you to the patchset when it hits LAK.
+
+/*
+ * tegra20_cpu_clear_resettable(void)
+ *
+ * Called to clear the "resettable soon" flag in PMC_SCRATCH41 when
+ * it is expected that the secondary CPU will be idle soon.
+ */
+ENTRY(tegra20_cpu_clear_resettable)
+ mov32 r1, TEGRA_PMC_VIRT + PMC_SCRATCH41
+ mov r12, #CPU_NOT_RESETTABLE
+ str r12, [r1]
+ mov pc, lr
+ENDPROC(tegra20_cpu_clear_resettable)
+
+/*
+ * tegra20_cpu_set_resettable_soon(void)
+ *
+ * Called to set the "resettable soon" flag in PMC_SCRATCH41 when
+ * it is expected that the secondary CPU will be idle soon.
+ */
+ENTRY(tegra20_cpu_set_resettable_soon)
+ mov32 r1, TEGRA_PMC_VIRT + PMC_SCRATCH41
+ mov r12, #CPU_RESETTABLE_SOON
+ str r12, [r1]
+ mov pc, lr
+ENDPROC(tegra20_cpu_set_resettable_soon)
+
+/*
+ * tegra20_sleep_cpu_secondary_finish(unsigned long v2p)
+ *
+ * Enters WFI on secondary CPU by exiting coherency.
+ */
+ENTRY(tegra20_sleep_cpu_secondary_finish)
+ mrc p15, 0, r11, c1, c0, 1 @ save actlr before exiting coherency
+
+ /* Flush and disable the L1 data cache */
+ bl tegra_disable_clean_inv_dcache
+
+ mov32 r0, TEGRA_PMC_VIRT + PMC_SCRATCH41
+ mov r3, #CPU_RESETTABLE
+ str r3, [r0]
+
+ bl cpu_do_idle
+
+ /*
+ * cpu may be reset while in wfi, which will return through
+ * tegra_resume to cpu_resume
+ * or interrupt may wake wfi, which will return here
+ * cpu state is unchanged - MMU is on, cache is on, coherency
+ * is off, and the data cache is off
+ *
+ * r11 contains the original actlr
+ */
+
+ bl tegra_pen_lock
+
+ mov32 r3, TEGRA_PMC_VIRT
+ add r0, r3, #PMC_SCRATCH41
+ mov r3, #CPU_NOT_RESETTABLE
+ str r3, [r0]
+
+ bl tegra_pen_unlock
+
+ /* Re-enable the data cache */
+ mrc p15, 0, r10, c1, c0, 0
+ orr r10, r10, #CR_C
+ mcr p15, 0, r10, c1, c0, 0
+ isb
+
+ mcr p15, 0, r11, c1, c0, 1 @ reenable coherency
+
+ /* Invalidate the TLBs & BTAC */
+ mov r1, #0
+ mcr p15, 0, r1, c8, c3, 0 @ invalidate shared TLBs
+ mcr p15, 0, r1, c7, c1, 6 @ invalidate shared BTAC
+ dsb
+ isb
+
+ /* the cpu was running with coherency disabled,
+ * caches may be out of date */
+ bl v7_flush_kern_cache_louis
+
+ ldmia sp!, {r1 - r3} @ pop phys pgd, virt SP, phys resume fn
+ mov r0, #0 @ return success
+ mov sp, r2 @ sp is stored in r2 by __cpu_suspend
This is not true. sp is retrieved from the r2 value popped above.
Anyway, all this code is a copy'n'paste from __cpu_suspend. Now if I got
what you want to do right, all you want to do is return to cpu_suspend
with r0 == 0.
(1) You should not rely on the register layout of __cpu_suspend since if
it changes we have to patch this code as well. Do not rely on that.
(2) Why do you want to return with r0 == 0 ? To me that's a mistery.
Is that because you want cpu_suspend to restore the page table
pointer ? Even in that case I am afraid I am against this code.
Usage of cpu_suspend must be consistent and you *must* not use it as a
plaster or rely on any specific register layout, it has to be used
for the purpose it has been designed for.
Lorenzo