On 02/17/2015 11:13 PM, Jan Kiszka wrote:
On 2015-02-17 22:03, Stephen Warren wrote:
On 02/16/2015 05:54 AM, Jan Kiszka wrote:
This is based on Thierry Reding's work and uses Ian Campell's preparatory patches. It comes with full support for CPU_ON/OFF PSCI services. The algorithm used in this version for turning CPUs on and off was proposed by Thierry Reding in http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/210881. It consists of first enabling CPU1..3 via the PMC, just to powergate them again with the help of the Flow Controller. Once the Flow Controller is in place, we can leave the PMC alone while processing CPU_ON and CPU_OFF PSCI requests.
diff --git a/arch/arm/cpu/armv7/tegra124/ap.c b/arch/arm/cpu/armv7/tegra124/ap.c
+void ap_pm_init(void) +{
- struct flow_ctlr *flow = (struct flow_ctlr *)NV_PA_FLOW_BASE;
- struct pmc_ctlr *pmc = (struct pmc_ctlr *)NV_PA_PMC_BASE;
- writel((u32)park_cpu, EXCEP_VECTOR_CPU_RESET_VECTOR);
- tegra_powergate_power_on(TEGRA_POWERGATE_CPU1);
- tegra_powergate_power_on(TEGRA_POWERGATE_CPU2);
- tegra_powergate_power_on(TEGRA_POWERGATE_CPU3);
- writel((2 << CSR_WAIT_WFI_SHIFT) | CSR_ENABLE, &flow->cpu1_csr);
- writel((4 << CSR_WAIT_WFI_SHIFT) | CSR_ENABLE, &flow->cpu2_csr);
- writel((8 << CSR_WAIT_WFI_SHIFT) | CSR_ENABLE, &flow->cpu3_csr);
- writel(EVENT_MODE_STOP, &flow->halt_cpu1_events);
- writel(EVENT_MODE_STOP, &flow->halt_cpu2_events);
- writel(EVENT_MODE_STOP, &flow->halt_cpu3_events);
I would expect to set up halt_cpu*_events before powering on the CPUs, to make sure that they do the expected action on the very first WFI. So, shouldn't the order above be:
Write to halt_cpu*_events Write to cpu*_csr power_on
Yeah, that was my original expectation as well. But
diff --git a/arch/arm/cpu/armv7/tegra124/ap.c b/arch/arm/cpu/armv7/tegra124/ap.c index eebc0ea..240c71d 100644 --- a/arch/arm/cpu/armv7/tegra124/ap.c +++ b/arch/arm/cpu/armv7/tegra124/ap.c @@ -25,10 +25,6 @@ void ap_pm_init(void)
writel((u32)park_cpu, EXCEP_VECTOR_CPU_RESET_VECTOR);
- tegra_powergate_power_on(TEGRA_POWERGATE_CPU1);
- tegra_powergate_power_on(TEGRA_POWERGATE_CPU2);
- tegra_powergate_power_on(TEGRA_POWERGATE_CPU3);
- writel((2 << CSR_WAIT_WFI_SHIFT) | CSR_ENABLE, &flow->cpu1_csr); writel((4 << CSR_WAIT_WFI_SHIFT) | CSR_ENABLE, &flow->cpu2_csr); writel((8 << CSR_WAIT_WFI_SHIFT) | CSR_ENABLE, &flow->cpu3_csr);
@@ -37,6 +33,10 @@ void ap_pm_init(void) writel(EVENT_MODE_STOP, &flow->halt_cpu2_events); writel(EVENT_MODE_STOP, &flow->halt_cpu3_events);
- tegra_powergate_power_on(TEGRA_POWERGATE_CPU1);
- tegra_powergate_power_on(TEGRA_POWERGATE_CPU2);
- tegra_powergate_power_on(TEGRA_POWERGATE_CPU3);
- while (readl(&pmc->pmc_pwrgate_status) & ((1 << TEGRA_POWERGATE_CPU1) | (1 << TEGRA_POWERGATE_CPU2) | (1 << TEGRA_POWERGATE_CPU3)))
doesn't work in practice. I suspect the power-on overwrites what the flow controller configures in the PMC beforehand. But maybe someone can explain this better than me.
Thierry, Peter, can you comment on why that is, and whether the original code sequence is safe; does it matter that the target CPU executes WFI before the flow controller is configured what to do on WFI?