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SubjectRe: [PATCH v1] irqchip/irq-sifive-plic: Add syscore callbacks for hibernation
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On 2023/2/6 20:48, Marc Zyngier wrote:
> On Mon, 06 Feb 2023 06:13:11 +0000,
> Mason Huo <mason.huo@starfivetech.com> wrote:
>>
>>
>>
>> On 2023/2/5 18:51, Marc Zyngier wrote:
>> > On Fri, 13 Jan 2023 09:42:16 +0000,
>> > Mason Huo <mason.huo@starfivetech.com> wrote:
>> >>
>> >> The priority and enable registers of plic will be reset
>> >> during hibernation power cycle in poweroff mode,
>> >> add the syscore callbacks to save/restore those registers.
>> >>
>> >> Signed-off-by: Mason Huo <mason.huo@starfivetech.com>
>> >> Reviewed-by: Ley Foon Tan <leyfoon.tan@starfivetech.com>
>> >> Reviewed-by: Sia Jee Heng <jeeheng.sia@starfivetech.com>
>> >> ---
>> >> drivers/irqchip/irq-sifive-plic.c | 93 ++++++++++++++++++++++++++++++-
>> >> 1 file changed, 91 insertions(+), 2 deletions(-)
>> >>
>> >> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
>> >> index ff47bd0dec45..80306de45d2b 100644
>> >> --- a/drivers/irqchip/irq-sifive-plic.c
>> >> +++ b/drivers/irqchip/irq-sifive-plic.c
>> >> @@ -17,6 +17,7 @@
>> >> #include <linux/of_irq.h>
>> >> #include <linux/platform_device.h>
>> >> #include <linux/spinlock.h>
>> >> +#include <linux/syscore_ops.h>
>> >> #include <asm/smp.h>
>> >>
>> >> /*
>> >> @@ -67,6 +68,8 @@ struct plic_priv {
>> >> struct irq_domain *irqdomain;
>> >> void __iomem *regs;
>> >> unsigned long plic_quirks;
>> >> + unsigned int nr_irqs;
>> >> + u32 *priority_reg;
>> >> };
>> >>
>> >> struct plic_handler {
>> >> @@ -79,10 +82,13 @@ struct plic_handler {
>> >> raw_spinlock_t enable_lock;
>> >> void __iomem *enable_base;
>> >> struct plic_priv *priv;
>> >> + /* To record interrupts that are enabled before suspend. */
>> >> + u32 enable_reg[MAX_DEVICES / 32];
>> >
>> > What does MAX_DEVICES represent here? How is it related to the number
>> > of interrupts you're trying to save? It seems to be related to the
>> > number of CPUs, so it hardly makes any sense so far.
>> >
>> The comment of this macro describes that "The largest number supported
>> by devices marked as 'sifive,plic-1.0.0', is 1024, of which
>> device 0 is defined as non-existent by the RISC-V Privileged Spec."
>> As far as I understand, the *device* here means HW IRQ source,
>> and the HW IRQ 0 is non-existent.
>
> So why is it sized to that maximum value? The binding gives you the
> *real* value that the HW implements.
>
OK, will change to use binding value.

>>
>> >> };
>> >> static int plic_parent_irq __ro_after_init;
>> >> static bool plic_cpuhp_setup_done __ro_after_init;
>> >> static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
>> >> +static struct plic_priv *priv_data;
>> >>
>> >> static int plic_irq_set_type(struct irq_data *d, unsigned int type);
>> >>
>> >> @@ -229,6 +235,78 @@ static int plic_irq_set_type(struct irq_data *d, unsigned int type)
>> >> return IRQ_SET_MASK_OK;
>> >> }
>> >>
>> >> +static void plic_irq_resume(void)
>> >> +{
>> >> + unsigned int i, cpu;
>> >> + u32 __iomem *reg;
>> >> +
>> >> + for (i = 0; i < priv_data->nr_irqs; i++)
>> >> + writel(priv_data->priority_reg[i],
>> >> + priv_data->regs + PRIORITY_BASE + i * PRIORITY_PER_ID);
>> >
>> > From what I can tell, this driver uses exactly 2 priorities: 0 and 1.
>> > And yet you use a full 32bit to encode those. Does it seem like a good
>> > idea?
>> >
>> Yes, currently this driver uses oly 2 priorities.
>> But, according to the sifive spec, the priority register is a 32bit register,
>> and it supports 7 levels of priority.
>
> And? This is a Linux driver, not an implementation validation
> tool. What is the point of saving/restoring stuff that is *never*
> used? :-(
>
> M.
> OK, will save/restore the priority in 1 bit.

Thanks
Mason

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