linux-kernel - Re: [PATCH] irqchip/gic-v3: workaround for ASR8601 when reading mpidr

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Message-ID: <86ttwbl5nq.wl-maz@kernel.org>
Date:   Wed, 17 May 2023 09:32:25 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     zhengyan <zhengyan@...micro.com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        meitaogao@...micro.com, qiaozhou@...micro.com,
        zhizhouzhang@...micro.com
Subject: Re: [PATCH] irqchip/gic-v3: workaround for ASR8601 when reading mpidr

On Wed, 17 May 2023 08:55:00 +0100,
zhengyan <zhengyan@...micro.com> wrote:
> 
> This patch add workaround for ASR8601, which uses an armv8.2
> processor with a gic-500. ARMv8.2 uses Multiprocessor Affinity
> Register to identify the logical address of the core by
> | cluster | core | thread |.

Not quite. The ARMv8.2 architecture doesn't say *any* of that. It is
ARM's *implementations* that follow this scheme.

> However, gic-500 only supports topologies with
> affinity levels less than 2 as
> | cluster | core|.
> 
> So it needs this patch to shift the MPIDR values
> to ensure proper functionality
> 
> Signed-off-by: zhengyan <zhengyan@...micro.com>
> ---
>  drivers/irqchip/irq-gic-v3.c | 28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 6fcee221f201..435b98a8641e 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -39,6 +39,7 @@
>  
>  #define FLAGS_WORKAROUND_GICR_WAKER_MSM8996	(1ULL << 0)
>  #define FLAGS_WORKAROUND_CAVIUM_ERRATUM_38539	(1ULL << 1)
> +#define FLAGS_WORKAROUND_MPIDR_ASR8601		(1ULL << 2)

What is ASR8601? Is it a system? Or an erratum number? For issues that
are the result of a HW integration issue, please provide an official
erratum number, and update Documentation/arm64/silicon-errata.rst.

>
>  #define GIC_IRQ_TYPE_PARTITION	(GIC_IRQ_TYPE_LPI + 1)
>  
> @@ -659,6 +660,9 @@ static u64 gic_mpidr_to_affinity(unsigned long mpidr)
>  {
>  	u64 aff;
>  
> +	if (gic_data.flags & FLAGS_WORKAROUND_MPIDR_ASR8601)
> +		mpidr >>= 8;
> +
>  	aff = ((u64)MPIDR_AFFINITY_LEVEL(mpidr, 3) << 32 |
>  	       MPIDR_AFFINITY_LEVEL(mpidr, 2) << 16 |
>  	       MPIDR_AFFINITY_LEVEL(mpidr, 1) << 8  |
> @@ -970,6 +974,9 @@ static int __gic_populate_rdist(struct redist_region *region, void __iomem *ptr)
>  	 * Convert affinity to a 32bit value that can be matched to
>  	 * GICR_TYPER bits [63:32].
>  	 */
> +	if (gic_data.flags & FLAGS_WORKAROUND_MPIDR_ASR8601)
> +		mpidr >>= 8;
> +
>  	aff = (MPIDR_AFFINITY_LEVEL(mpidr, 3) << 24 |
>  	       MPIDR_AFFINITY_LEVEL(mpidr, 2) << 16 |
>  	       MPIDR_AFFINITY_LEVEL(mpidr, 1) << 8 |
> @@ -1265,6 +1272,8 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
>  	unsigned long mpidr = cpu_logical_map(cpu);
>  	u16 tlist = 0;
>  
> +	if (gic_data.flags & FLAGS_WORKAROUND_MPIDR_ASR8601)
> +		mpidr >>= 8;
>  	while (cpu < nr_cpu_ids) {
>  		tlist |= 1 << (mpidr & 0xf);
>  
> @@ -1274,7 +1283,8 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
>  		cpu = next_cpu;
>  
>  		mpidr = cpu_logical_map(cpu);
> -
> +		if (gic_data.flags & FLAGS_WORKAROUND_MPIDR_ASR8601)
> +			mpidr >>= 8;
>  		if (cluster_id != MPIDR_TO_SGI_CLUSTER_ID(mpidr)) {
>  			cpu--;
>  			goto out;
> @@ -1321,6 +1331,8 @@ static void gic_ipi_send_mask(struct irq_data *d, const struct cpumask *mask)
>  		u64 cluster_id = MPIDR_TO_SGI_CLUSTER_ID(cpu_logical_map(cpu));
>  		u16 tlist;
>  
> +		if (gic_data.flags & FLAGS_WORKAROUND_MPIDR_ASR8601)
> +			cluster_id = MPIDR_TO_SGI_CLUSTER_ID(cpu_logical_map(cpu) >> 8);

You've written the same check 5 times. Maybe you could start by
refactoring that code so that the hack can be in a single place?

>  		tlist = gic_compute_target_list(&cpu, mask, cluster_id);
>  		gic_send_sgi(cluster_id, tlist, d->hwirq);
>  	}
> @@ -1729,6 +1741,15 @@ static bool gic_enable_quirk_cavium_38539(void *data)
>  	return true;
>  }
>  
> +static bool gic_enable_quirk_asr8601(void *data)
> +{
> +	struct gic_chip_data *d = data;
> +
> +	d->flags |= FLAGS_WORKAROUND_MPIDR_ASR8601;
> +
> +	return true;
> +}
> +
>  static bool gic_enable_quirk_hip06_07(void *data)
>  {
>  	struct gic_chip_data *d = data;
> @@ -1823,6 +1844,11 @@ static const struct gic_quirk gic_quirks[] = {
>  		.mask	= 0xffffffff,
>  		.init	= gic_enable_quirk_nvidia_t241,
>  	},
> +	{
> +		.desc	= "GICv3: ASR 8601 MPIDR SHIFT",

s/SHIFT/shift/

> +		.compatible = "asr,asr8601-gic-v3",

So ASR8601 *is* a system... Is it DT only?

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.