Re: [PATCH] fsl/smp: add low power boot support to replace spin boot
From: Scott Wood <hidden>
Date: 2015-01-20 00:46:20
On Thu, 2015-01-15 at 14:05 +0800, Dongsheng Wang wrote:
From: Wang Dongsheng <redacted> U-boot put non-boot cpus into an low power state(PW10/PW20 or DOZE) when cpu powered up. To exit low power state kernel will send DOORBELL or MPIC-IPI signal to all those CPUs.
U-Boot does not do this yet. A patch was just posted to propose such a change.
quoted hunk ↗ jump to hunk
@@ -292,11 +315,58 @@ static int smp_85xx_kick_cpu(int nr) __secondary_hold_acknowledge = -1; } #endif + flush_spin_table(spin_table); - out_be32(&spin_table->pir, hw_cpu); + /* + * U-boot will wait kernel send eoi to MPIC, after EOI has send + * kernel will set PIR for uboot, let uboot know EOI has send. + */ + out_be32(&spin_table->pir, 0);
Why is the kernel sending EOI for an interrupt U-Boot receives? Why are you abusing PIR for anything other than setting the desired PIR value? What happens when you enter the kernel with secondaries having PIR = 0?
+ /* Let cpu exit low power state, and from u-boot jump to kernel */ + arch_send_call_function_single_ipi(kick_cpus); + + /* + * Let we ACK interrput and Send EOI signal to finish INT server + * U-boot has read EPR to ACK interrput when MPIC work in external + * proxy mode. Without the external proxy facility, we need to read + * MPIC ACK register. + * + * There just ACK interrput, we don't need to get the interrupt vector + * and to handle it. Because there just IPI or DOORBELL interrupt to + * make u-boot exit low power state and jump to kernel. + */ + mpic_cpu_ack(nr);
How do you know the interrupt is ready to be acked at this point? -Scott