linux-kernel - Re: [PATCH] irqchip: gic-v3: Handle failure case of CPU enters low power state

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Date:   Tue, 27 Dec 2022 16:06:38 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Yogesh Lal <quic_ylal@...cinc.com>
CC:     <tglx@...utronix.de>, <maz@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH] irqchip: gic-v3: Handle failure case of CPU enters low
 power state

Hi Yogesh,

On Fri, Dec 23, 2022 at 12:05:40AM +0530, Yogesh Lal wrote:
> When CPU enter in low power mode it disable the redistributor and
> Group1 interrupts. And re-initialise the system registers on wakeup.
> 
> But in case of failure to enter low power mode need to enable
> the redistributor and Group1 interrupts.
> 
> Signed-off-by: Yogesh Lal <quic_ylal@...cinc.com>
> ---
>  drivers/irqchip/irq-gic-v3.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 997104d..4904f00 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -1376,7 +1376,7 @@ static int gic_retrigger(struct irq_data *data)
>  static int gic_cpu_pm_notifier(struct notifier_block *self,
>  			       unsigned long cmd, void *v)
>  {
> -	if (cmd == CPU_PM_EXIT) {
> +	if (cmd == CPU_PM_EXIT || cmd == CPU_PM_ENTER_FAILED) {
>  		if (gic_dist_security_disabled())
>  			gic_enable_redist(true);
>  		gic_cpu_sys_reg_init();

static int gic_cpu_pm_notifier(struct notifier_block *self,
			       unsigned long cmd, void *v)
{
	if (cmd == CPU_PM_EXIT) {
		if (gic_dist_security_disabled())
			gic_enable_redist(true);
		gic_cpu_sys_reg_init();
	} else if (cmd == CPU_PM_ENTER && gic_dist_security_disabled()) {
		gic_write_grpen1(0);
		gic_enable_redist(false);
	}
	return NOTIFY_OK;
}

During CPU_PM_ENTER notification, we are not doing anything for the
!gic_dist_security_disabled() case. Since CPU_PM_ENTER_FAILED notification
arrive when CPU fails to power down, do we need to reinitialize the
system registers? IOW, should we do different handling for CPU_PM_ENTER_FAILED
based on gic_dist_security_disabled()?

Thanks,
Pavan