Re: [PATCH v2] irqchip/gic-v3: workaround for ASR8601 when reading mpidr

[Marc Zyngier <maz@kernel.org>]

On Mon, 22 May 2023 12:06:43 +0100,
zhengyan <zhengyan@asrmicro.com> wrote:
> 
> This patch add workaround for ASR8601, which uses an armv8.2
> processor with a gic-500. But gic-500 is incompatible with
> ARMv8.2 implementations from ARM.
> 
> ARMv8.2 from ARM implementation uses Multiprocessor Affinity
> Register to identify the logical address of the core by
> | cluster | core | thread |.
> However, gic-500 only supports topologies with
> affinity levels less than 2 as
> | cluster | core|.
> 
> So we need this patch as workaround to shift the MPIDR values
> to ensure proper functionality
> 
> Signed-off-by: zhengyan <zhengyan@asrmicro.com>
> ---
>  Documentation/arm64/silicon-errata.rst |  4 ++++
>  drivers/irqchip/irq-gic-v3.c           | 30 ++++++++++++++++++++++++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst
> index 9e311bc43e05..d6430ade349d 100644
> --- a/Documentation/arm64/silicon-errata.rst
> +++ b/Documentation/arm64/silicon-errata.rst
> @@ -214,3 +214,7 @@ stable kernels.
>  +----------------+-----------------+-----------------+-----------------------------+
>  | Fujitsu        | A64FX           | E#010001        | FUJITSU_ERRATUM_010001      |
>  +----------------+-----------------+-----------------+-----------------------------+
> +
> ++----------------+-----------------+-----------------+-----------------------------+
> +| ASR            | ASR8601         | #8601001        | N/A                         |
> ++----------------+-----------------+-----------------+-----------------------------+
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 6fcee221f201..cf64783dfe70 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -39,6 +39,9 @@
>  
>  #define FLAGS_WORKAROUND_GICR_WAKER_MSM8996	(1ULL << 0)
>  #define FLAGS_WORKAROUND_CAVIUM_ERRATUM_38539	(1ULL << 1)
> +#define FLAGS_WORKAROUND_ASR_ERRATUM_8601001	(1ULL << 2)
> +
> +#define ASR8601_AFF_QUIRK(aff)			(aff >> 8)

This is wrong. There are more than just affinity bits in MPIDR, and
you're making a mess of the result.

>  
>  #define GIC_IRQ_TYPE_PARTITION	(GIC_IRQ_TYPE_LPI + 1)
>  
> @@ -659,6 +662,9 @@ static u64 gic_mpidr_to_affinity(unsigned long mpidr)
>  {
>  	u64 aff;
>  
> +	if (gic_data.flags & FLAGS_WORKAROUND_ASR_ERRATUM_8601001)
> +		mpidr = ASR8601_AFF_QUIRK(mpidr);
> +
>  	aff = ((u64)MPIDR_AFFINITY_LEVEL(mpidr, 3) << 32 |
>  	       MPIDR_AFFINITY_LEVEL(mpidr, 2) << 16 |
>  	       MPIDR_AFFINITY_LEVEL(mpidr, 1) << 8  |
> @@ -970,6 +976,9 @@ 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_ASR_ERRATUM_8601001)
> +		mpidr = ASR8601_AFF_QUIRK(mpidr);

It really wasn't what I had in mind when I asked you to place this
inside a helper. The whole thing looks horrible, and I really don't
want to have to maintain anything like it.

I came up with the following patch, which keeps the workaround *in a
single spot*.

Let me know if that works for you.

	M.

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 6fcee221f201..b7d69ef4da9f 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_ASR_ERRATUM_8601001	(1ULL << 2)
 
 #define GIC_IRQ_TYPE_PARTITION	(GIC_IRQ_TYPE_LPI + 1)
 
@@ -655,10 +656,16 @@ static int gic_irq_set_vcpu_affinity(struct irq_data *d, void *vcpu)
 	return 0;
 }
 
-static u64 gic_mpidr_to_affinity(unsigned long mpidr)
+static u64 gic_cpu_to_affinity(int cpu)
 {
+	u64 mpidr = cpu_logical_map(cpu);
 	u64 aff;
 
+	/* ASR8601 needs to have its affinities shifted down... */
+	if (unlikely(gic_data.flags & FLAGS_WORKAROUND_ASR_ERRATUM_8601001))
+		mpidr = (MPIDR_AFFINITY_LEVEL(mpidr, 1)	|
+			 (MPIDR_AFFINITY_LEVEL(mpidr, 2) << 8));
+
 	aff = ((u64)MPIDR_AFFINITY_LEVEL(mpidr, 3) << 32 |
 	       MPIDR_AFFINITY_LEVEL(mpidr, 2) << 16 |
 	       MPIDR_AFFINITY_LEVEL(mpidr, 1) << 8  |
@@ -913,7 +920,7 @@ static void __init gic_dist_init(void)
 	 * Set all global interrupts to the boot CPU only. ARE must be
 	 * enabled.
 	 */
-	affinity = gic_mpidr_to_affinity(cpu_logical_map(smp_processor_id()));
+	affinity = gic_cpu_to_affinity(smp_processor_id());
 	for (i = 32; i < GIC_LINE_NR; i++)
 		gic_write_irouter(affinity, base + GICD_IROUTER + i * 8);
 
@@ -962,7 +969,7 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *))
 
 static int __gic_populate_rdist(struct redist_region *region, void __iomem *ptr)
 {
-	unsigned long mpidr = cpu_logical_map(smp_processor_id());
+	unsigned long mpidr;
 	u64 typer;
 	u32 aff;
 
@@ -970,6 +977,8 @@ 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].
 	 */
+	mpidr = gic_cpu_to_affinity(smp_processor_id());
+
 	aff = (MPIDR_AFFINITY_LEVEL(mpidr, 3) << 24 |
 	       MPIDR_AFFINITY_LEVEL(mpidr, 2) << 16 |
 	       MPIDR_AFFINITY_LEVEL(mpidr, 1) << 8 |
@@ -1262,9 +1271,11 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
 				   unsigned long cluster_id)
 {
 	int next_cpu, cpu = *base_cpu;
-	unsigned long mpidr = cpu_logical_map(cpu);
+	unsigned long mpidr;
 	u16 tlist = 0;
 
+	mpidr = gic_cpu_to_affinity(cpu);
+
 	while (cpu < nr_cpu_ids) {
 		tlist |= 1 << (mpidr & 0xf);
 
@@ -1273,8 +1284,7 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
 			goto out;
 		cpu = next_cpu;
 
-		mpidr = cpu_logical_map(cpu);
-
+		mpidr = gic_cpu_to_affinity(cpu);
 		if (cluster_id != MPIDR_TO_SGI_CLUSTER_ID(mpidr)) {
 			cpu--;
 			goto out;
@@ -1318,7 +1328,7 @@ static void gic_ipi_send_mask(struct irq_data *d, const struct cpumask *mask)
 	dsb(ishst);
 
 	for_each_cpu(cpu, mask) {
-		u64 cluster_id = MPIDR_TO_SGI_CLUSTER_ID(cpu_logical_map(cpu));
+		u64 cluster_id = MPIDR_TO_SGI_CLUSTER_ID(gic_cpu_to_affinity(cpu));
 		u16 tlist;
 
 		tlist = gic_compute_target_list(&cpu, mask, cluster_id);
@@ -1376,7 +1386,7 @@ static int gic_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
 
 	offset = convert_offset_index(d, GICD_IROUTER, &index);
 	reg = gic_dist_base(d) + offset + (index * 8);
-	val = gic_mpidr_to_affinity(cpu_logical_map(cpu));
+	val = gic_cpu_to_affinity(cpu);
 
 	gic_write_irouter(val, reg);
 
@@ -1786,6 +1796,15 @@ static bool gic_enable_quirk_nvidia_t241(void *data)
 	return true;
 }
 
+static bool gic_enable_quirk_asr8601(void *data)
+{
+	struct gic_chip_data *d = data;
+
+	d->flags |= FLAGS_WORKAROUND_ASR_ERRATUM_8601001;
+
+	return true;
+}
+
 static const struct gic_quirk gic_quirks[] = {
 	{
 		.desc	= "GICv3: Qualcomm MSM8996 broken firmware",
@@ -1823,6 +1842,11 @@ static const struct gic_quirk gic_quirks[] = {
 		.mask	= 0xffffffff,
 		.init	= gic_enable_quirk_nvidia_t241,
 	},
+	{
+		.desc	= "GICv3: ASR erratum 8601001",
+		.compatible = "asr,asr8601-gic-v3",
+		.init	= gic_enable_quirk_asr8601,
+	},
 	{
 	}
 };


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