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02e75d6488
Prior to this change, {save,restore}_cpu_arch_register() collaborated to maintain the value of the CPU diagnostic register across power cycles. This was required to maintain any CPU errata workaround enable bits in that register. However, now that the Tegra reset vector code always enables all required workarounds, there is no need to save and restore the diagnostic register; it is always explicitly programmed in the required manner. Hence, remove the save/restore logic. This has the advantage that the kernel always directly controls the value of this register every boot, rather than relying on a bootloader or other kernel code having previously written the correct value into it. This makes CPU0 (which was previously saved/restored) and CPUn (which should have been set up by the reset vector) be controlled in exactly the same way, which is easier to debug/find/... In particular, when converting Tegra to a multi-platform kernel, the CPU0 diagnostic register value initially comes from the bootloader. Most Tegra bootloaders don't yet enable all required CPU bug workarounds. The previous commit updates the kernel to do so on any CPU power cycle. However, the save/restore code ends up over-writing the value with the old bootloader-driven value instead of the now more-likely-to-be-correct kernel value! Even irrespective of multi-platform conversion, this change limits the kernel's exposure to any WARs the bootloader didn't enable for CPU0: on the very first LP2 transition (CPU power-saving which power-cycles the CPU), the correct value will be enabled. Signed-off-by: Stephen Warren <swarren@nvidia.com>
185 lines
4.2 KiB
C
185 lines
4.2 KiB
C
/*
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* CPU idle driver for Tegra CPUs
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*
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* Copyright (c) 2010-2012, NVIDIA Corporation.
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* Copyright (c) 2011 Google, Inc.
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* Author: Colin Cross <ccross@android.com>
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* Gary King <gking@nvidia.com>
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*
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* Rework for 3.3 by Peter De Schrijver <pdeschrijver@nvidia.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/cpuidle.h>
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#include <linux/cpu_pm.h>
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#include <linux/clockchips.h>
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#include <linux/clk/tegra.h>
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#include <asm/cpuidle.h>
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#include <asm/proc-fns.h>
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#include <asm/suspend.h>
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#include <asm/smp_plat.h>
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#include "pm.h"
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#include "sleep.h"
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#ifdef CONFIG_PM_SLEEP
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static int tegra30_idle_lp2(struct cpuidle_device *dev,
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struct cpuidle_driver *drv,
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int index);
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#endif
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static struct cpuidle_driver tegra_idle_driver = {
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.name = "tegra_idle",
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.owner = THIS_MODULE,
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.en_core_tk_irqen = 1,
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#ifdef CONFIG_PM_SLEEP
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.state_count = 2,
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#else
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.state_count = 1,
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#endif
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.states = {
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[0] = ARM_CPUIDLE_WFI_STATE_PWR(600),
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#ifdef CONFIG_PM_SLEEP
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[1] = {
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.enter = tegra30_idle_lp2,
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.exit_latency = 2000,
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.target_residency = 2200,
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.power_usage = 0,
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.flags = CPUIDLE_FLAG_TIME_VALID,
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.name = "powered-down",
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.desc = "CPU power gated",
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},
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#endif
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},
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};
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static DEFINE_PER_CPU(struct cpuidle_device, tegra_idle_device);
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#ifdef CONFIG_PM_SLEEP
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static bool tegra30_cpu_cluster_power_down(struct cpuidle_device *dev,
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struct cpuidle_driver *drv,
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int index)
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{
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struct cpuidle_state *state = &drv->states[index];
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u32 cpu_on_time = state->exit_latency;
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u32 cpu_off_time = state->target_residency - state->exit_latency;
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/* All CPUs entering LP2 is not working.
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* Don't let CPU0 enter LP2 when any secondary CPU is online.
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*/
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if (num_online_cpus() > 1 || !tegra_cpu_rail_off_ready()) {
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cpu_do_idle();
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return false;
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}
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clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu);
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tegra_idle_lp2_last(cpu_on_time, cpu_off_time);
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clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);
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return true;
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}
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#ifdef CONFIG_SMP
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static bool tegra30_cpu_core_power_down(struct cpuidle_device *dev,
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struct cpuidle_driver *drv,
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int index)
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{
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clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu);
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smp_wmb();
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cpu_suspend(0, tegra30_sleep_cpu_secondary_finish);
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clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);
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return true;
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}
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#else
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static inline bool tegra30_cpu_core_power_down(struct cpuidle_device *dev,
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struct cpuidle_driver *drv,
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int index)
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{
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return true;
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}
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#endif
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static int tegra30_idle_lp2(struct cpuidle_device *dev,
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struct cpuidle_driver *drv,
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int index)
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{
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u32 cpu = is_smp() ? cpu_logical_map(dev->cpu) : dev->cpu;
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bool entered_lp2 = false;
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bool last_cpu;
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local_fiq_disable();
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last_cpu = tegra_set_cpu_in_lp2(cpu);
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cpu_pm_enter();
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if (cpu == 0) {
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if (last_cpu)
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entered_lp2 = tegra30_cpu_cluster_power_down(dev, drv,
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index);
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else
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cpu_do_idle();
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} else {
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entered_lp2 = tegra30_cpu_core_power_down(dev, drv, index);
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}
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cpu_pm_exit();
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tegra_clear_cpu_in_lp2(cpu);
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local_fiq_enable();
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smp_rmb();
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return (entered_lp2) ? index : 0;
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}
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#endif
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int __init tegra30_cpuidle_init(void)
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{
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int ret;
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unsigned int cpu;
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struct cpuidle_device *dev;
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struct cpuidle_driver *drv = &tegra_idle_driver;
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#ifdef CONFIG_PM_SLEEP
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tegra_tear_down_cpu = tegra30_tear_down_cpu;
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#endif
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ret = cpuidle_register_driver(&tegra_idle_driver);
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if (ret) {
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pr_err("CPUidle driver registration failed\n");
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return ret;
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}
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for_each_possible_cpu(cpu) {
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dev = &per_cpu(tegra_idle_device, cpu);
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dev->cpu = cpu;
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dev->state_count = drv->state_count;
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ret = cpuidle_register_device(dev);
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if (ret) {
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pr_err("CPU%u: CPUidle device registration failed\n",
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cpu);
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return ret;
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}
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}
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return 0;
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}
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