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

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Message-ID: <e6377027-c4e5-4fd2-abf4-63cf6282542d@gmail.com>
Date: Thu, 29 Aug 2024 22:06:56 +0800
From: Nick Chan <towinchenmi@...il.com>
To: Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>,
 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
Cc: ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH RESEND 3/3] irqchip/apple-aic: Add a new "Global fast IPIs
 only" feature level



On 29/8/2024 19:02, Nick Chan 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>
> ---
>  drivers/irqchip/irq-apple-aic.c | 25 ++++++++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c
> index 626aaeafa96c..1640074af2e1 100644
> --- a/drivers/irqchip/irq-apple-aic.c
> +++ b/drivers/irqchip/irq-apple-aic.c
> @@ -236,6 +236,8 @@ enum fiq_hwirq {
>  
>  /* True if UNCORE/UNCORE2 and Sn_... IPI registers are present and used (A11+) */
>  static DEFINE_STATIC_KEY_TRUE(use_fast_ipi);
> +/* True if SYS_IMP_APL_IPI_RR_LOCAL_EL1 exists (M1+) */
> +static DEFINE_STATIC_KEY_TRUE(use_local_fast_ipi);
>  
>  struct aic_info {
>  	int version;
> @@ -253,6 +255,7 @@ struct aic_info {
>  
>  	/* Features */
>  	bool fast_ipi;
> +	bool local_fast_ipi;
>  };
>  
>  static const struct aic_info aic1_info __initconst = {
> @@ -271,6 +274,16 @@ 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 = {
This patch is incorrectly disabling local fast IPI on aic2, it will be
corrected in v2.

>  	.version	= 2,
>  
> @@ -282,6 +295,10 @@ static const struct aic_info aic2_info __initconst = {
>  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,
>  	},
>  	{
> @@ -748,7 +765,8 @@ 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
> @@ -992,6 +1010,11 @@ static int __init aic_of_ic_init(struct device_node *node, struct device_node *p
>  	else
>  		static_branch_disable(&use_fast_ipi);
>  
> +	if (irqc->info.local_fast_ipi)
> +		static_branch_enable(&use_local_fast_ipi);
> +	else
> +		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),

Nick Chan