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Date: Fri, 9 Apr 2021 10:17:25 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Valentin Schneider <valentin.schneider@....com>
CC: <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
Marc Zyngier <maz@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
"Lorenzo Pieralisi" <lorenzo.pieralisi@....com>,
Vincenzo Frascino <vincenzo.frascino@....com>
Subject: Re: [RFC PATCH 01/10] genirq: Add chip flag to denote automatic IRQ
(un)masking
On Thu, 8 Apr 2021 16:43:17 +0100
Valentin Schneider <valentin.schneider@....com> wrote:
> Some IRQ chips such as the Arm GICs automagically mask / unmask an
> IRQ during the handling of said IRQ. This renders further mask / unmask
> operations within the flow handlers redundant, which we do want to leverage
> as masking by itself is not cheap (Distributor access via MMIO for GICs).
>
> This is different from having a chip->irq_mask_ack() callback as this
> masking is:
> - inherent to the chip->irq_ack() and *cannot* be omitted
> - a *different* masking state than chip->irq_mask() (chip->irq_mask() is
> idempotent, chip->irq_ack() really isn't)
>
> Add a chip flag, IRQCHIP_AUTOMASKS_FLOW, to denote chips with such
> behaviour. Add a new IRQ data flag, IRQD_IRQ_FLOW_MASKED, to keep this
> flow-induced mask state separate from regular mask / unmask operations
> (IRQD_IRQ_MASKED).
>
> Signed-off-by: Valentin Schneider <valentin.schneider@....com>
Hi Valentin,
One totally trivial thing noticed whilst reading.
> ---
> include/linux/irq.h | 10 ++++++++++
> kernel/irq/chip.c | 5 +++++
> kernel/irq/debugfs.c | 2 ++
> kernel/irq/internals.h | 5 +++++
> 4 files changed, 22 insertions(+)
>
> diff --git a/include/linux/irq.h b/include/linux/irq.h
> index bee82809107c..580b1b6b1799 100644
> --- a/include/linux/irq.h
> +++ b/include/linux/irq.h
> @@ -219,6 +219,8 @@ struct irq_data {
> * irq_chip::irq_set_affinity() when deactivated.
> * IRQD_IRQ_ENABLED_ON_SUSPEND - Interrupt is enabled on suspend by irq pm if
> * irqchip have flag IRQCHIP_ENABLE_WAKEUP_ON_SUSPEND set.
> + * IRQD_IRQ_FLOW_MASKED - Interrupt is masked by ACK. Only EOI can
> + * clear this.
Nitpick of the day : Seems text above is using tabs for white space blocks
whereas you have used spaces. Make it consistent.
It's not consistent in the file so I guess you could clean that up, or
just go with making it consistent in this block.
> */
> enum {
> IRQD_TRIGGER_MASK = 0xf,
> @@ -245,6 +247,7 @@ enum {
> IRQD_HANDLE_ENFORCE_IRQCTX = (1 << 28),
> IRQD_AFFINITY_ON_ACTIVATE = (1 << 29),
> IRQD_IRQ_ENABLED_ON_SUSPEND = (1 << 30),
> + IRQD_IRQ_FLOW_MASKED = (1 << 31),
> };
>
> #define __irqd_to_state(d) ACCESS_PRIVATE((d)->common, state_use_accessors)
> @@ -349,6 +352,11 @@ static inline bool irqd_irq_masked(struct irq_data *d)
> return __irqd_to_state(d) & IRQD_IRQ_MASKED;
> }
>
> +static inline bool irqd_irq_flow_masked(struct irq_data *d)
> +{
> + return __irqd_to_state(d) & IRQD_IRQ_FLOW_MASKED;
> +}
> +
> static inline bool irqd_irq_inprogress(struct irq_data *d)
> {
> return __irqd_to_state(d) & IRQD_IRQ_INPROGRESS;
> @@ -567,6 +575,7 @@ struct irq_chip {
> * IRQCHIP_SUPPORTS_NMI: Chip can deliver NMIs, only for root irqchips
> * IRQCHIP_ENABLE_WAKEUP_ON_SUSPEND: Invokes __enable_irq()/__disable_irq() for wake irqs
> * in the suspend path if they are in disabled state
> + * IRQCHIP_AUTOMASKS_FLOW: chip->ack() masks and chip->eoi() unmasks
> */
> enum {
> IRQCHIP_SET_TYPE_MASKED = (1 << 0),
> @@ -579,6 +588,7 @@ enum {
> IRQCHIP_SUPPORTS_LEVEL_MSI = (1 << 7),
> IRQCHIP_SUPPORTS_NMI = (1 << 8),
> IRQCHIP_ENABLE_WAKEUP_ON_SUSPEND = (1 << 9),
> + IRQCHIP_AUTOMASKS_FLOW = (1 << 10),
> };
>
> #include <linux/irqdesc.h>
> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
> index 8cc8e5713287..18c3b0e1568a 100644
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -173,6 +173,11 @@ static void irq_state_clr_masked(struct irq_desc *desc)
> irqd_clear(&desc->irq_data, IRQD_IRQ_MASKED);
> }
>
> +static void irq_state_clr_flow_masked(struct irq_desc *desc)
> +{
> + irqd_clear(&desc->irq_data, IRQD_IRQ_FLOW_MASKED);
> +}
> +
> static void irq_state_clr_started(struct irq_desc *desc)
> {
> irqd_clear(&desc->irq_data, IRQD_IRQ_STARTED);
> diff --git a/kernel/irq/debugfs.c b/kernel/irq/debugfs.c
> index e4cff358b437..3ae83622d701 100644
> --- a/kernel/irq/debugfs.c
> +++ b/kernel/irq/debugfs.c
> @@ -58,6 +58,7 @@ static const struct irq_bit_descr irqchip_flags[] = {
> BIT_MASK_DESCR(IRQCHIP_SUPPORTS_LEVEL_MSI),
> BIT_MASK_DESCR(IRQCHIP_SUPPORTS_NMI),
> BIT_MASK_DESCR(IRQCHIP_ENABLE_WAKEUP_ON_SUSPEND),
> + BIT_MASK_DESCR(IRQCHIP_AUTOMASKS_FLOW),
> };
>
> static void
> @@ -103,6 +104,7 @@ static const struct irq_bit_descr irqdata_states[] = {
> BIT_MASK_DESCR(IRQD_IRQ_STARTED),
> BIT_MASK_DESCR(IRQD_IRQ_DISABLED),
> BIT_MASK_DESCR(IRQD_IRQ_MASKED),
> + BIT_MASK_DESCR(IRQD_IRQ_FLOW_MASKED),
> BIT_MASK_DESCR(IRQD_IRQ_INPROGRESS),
>
> BIT_MASK_DESCR(IRQD_PER_CPU),
> diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
> index 54363527feea..b6c1cceddec0 100644
> --- a/kernel/irq/internals.h
> +++ b/kernel/irq/internals.h
> @@ -245,6 +245,11 @@ static inline void irq_state_set_masked(struct irq_desc *desc)
> irqd_set(&desc->irq_data, IRQD_IRQ_MASKED);
> }
>
> +static inline void irq_state_set_flow_masked(struct irq_desc *desc)
> +{
> + irqd_set(&desc->irq_data, IRQD_IRQ_FLOW_MASKED);
> +}
> +
> #undef __irqd_to_state
>
> static inline void __kstat_incr_irqs_this_cpu(struct irq_desc *desc)
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