linux-kernel - Re: [PATCH v2 3/4] irqchip/apple-aic: Add a new "Global fast IPIs only" feature level

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Message-Id: <612CCDB4-26A7-432C-89F9-48743D547859@svenpeter.dev>
Date: Sat, 31 Aug 2024 09:05:50 +0200
From: Sven Peter <sven@...npeter.dev>
To: Nick Chan <towinchenmi@...il.com>
Cc: Hector Martin <marcan@...can.st>,
 Alyssa Rosenzweig <alyssa@...enzweig.io>,
 Thomas Gleixner <tglx@...utronix.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, asahi@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, konrad.dybcio@...ainline.org,
 ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v2 3/4] irqchip/apple-aic: Add a new "Global fast IPIs only" feature level


> 
> On 31. Aug 2024, at 07:57, Nick Chan <towinchenmi@...il.com> wrote:
> 
> Starting with the A11 (T8015) SoC, Apple began using arm64 sysregs for
> fast IPIs. However, on A11, there is no such things as "Local" fast IPIs,
> as the SYS_IMP_APL_IPI_RR_LOCAL_EL1 register does not seem to exist.
> 
> Add a new feature level, used by the compatible "apple,t8015-aic",
> controlled by a static branch key named use_local_fast_ipi. When
> use_fast_ipi is true and use_local_fast_ipi is false, fast IPIs are used
> but all IPIs goes through the register SYS_IMP_APL_IPI_RR_GLOBAL_EL1, as
> "global" IPIs.
> 
> Signed-off-by: Nick Chan <towinchenmi@...il.com>
> ---

Reviewed-by: Sven Peter <sven@...npeter.dev>

> drivers/irqchip/irq-apple-aic.c | 24 +++++++++++++++++++++++-
> 1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c
> index 8d81d5fb3c50..01a3c79054f5 100644
> --- a/drivers/irqchip/irq-apple-aic.c
> +++ b/drivers/irqchip/irq-apple-aic.c
> @@ -235,6 +235,8 @@ enum fiq_hwirq {
> };
> 
> static DEFINE_STATIC_KEY_TRUE(use_fast_ipi);
> +/* True if SYS_IMP_APL_IPI_RR_LOCAL_EL1 exists for local fast IPIs (M1+) */
> +static DEFINE_STATIC_KEY_TRUE(use_local_fast_ipi);
> 
> struct aic_info {
>    int version;
> @@ -252,6 +254,7 @@ struct aic_info {
> 
>    /* Features */
>    bool fast_ipi;
> +    bool local_fast_ipi;
> };
> 
> static const struct aic_info aic1_info __initconst = {
> @@ -270,17 +273,32 @@ static const struct aic_info aic1_fipi_info __initconst = {
>    .fast_ipi    = true,
> };
> 
> +static const struct aic_info aic1_local_fipi_info __initconst = {
> +    .version    = 1,
> +
> +    .event        = AIC_EVENT,
> +    .target_cpu    = AIC_TARGET_CPU,
> +
> +    .fast_ipi    = true,
> +    .local_fast_ipi = true,
> +};
> +
> static const struct aic_info aic2_info __initconst = {
>    .version    = 2,
> 
>    .irq_cfg    = AIC2_IRQ_CFG,
> 
>    .fast_ipi    = true,
> +    .local_fast_ipi = true,
> };
> 
> static const struct of_device_id aic_info_match[] = {
>    {
>        .compatible = "apple,t8103-aic",
> +        .data = &aic1_local_fipi_info,
> +    },
> +    {
> +        .compatible = "apple,t8015-aic",
>        .data = &aic1_fipi_info,
>    },
>    {
> @@ -750,7 +768,8 @@ static void aic_ipi_send_fast(int cpu)
>    u64 cluster = MPIDR_CLUSTER(mpidr);
>    u64 idx = MPIDR_CPU(mpidr);
> 
> -    if (MPIDR_CLUSTER(my_mpidr) == cluster)
> +    if (static_branch_likely(&use_local_fast_ipi) &&
> +        MPIDR_CLUSTER(my_mpidr) == cluster)
>        write_sysreg_s(FIELD_PREP(IPI_RR_CPU, idx),
>                   SYS_IMP_APL_IPI_RR_LOCAL_EL1);
>    else
> @@ -990,6 +1009,9 @@ static int __init aic_of_ic_init(struct device_node *node, struct device_node *p
>    if (!irqc->info.fast_ipi)
>        static_branch_disable(&use_fast_ipi);
> 
> +    if (!irqc->info.local_fast_ipi)
> +        static_branch_disable(&use_local_fast_ipi);
> +
>    irqc->info.die_stride = off - start_off;
> 
>    irqc->hw_domain = irq_domain_create_tree(of_node_to_fwnode(node),
> --
> 2.46.0
>