irqchip/gic-v3: Work around affinity issues on ASR8601

The ASR8601 SoC combines ARMv8.2 CPUs from ARM with a GIC-500,
also from ARM. However, the two are incompatible as the former
expose an affinity in the form of (cluster, core, thread),
while the latter can only deal with (cluster, core). If nothing
is done, the GIC simply cannot route interrupts to the CPUs.

Implement a workaround that shifts the affinity down by a level,
ensuring the delivery of interrupts despite the implementation
mismatch.

Signed-off-by: zhengyan <zhengyan@asrmicro.com>
[maz: rewrote commit message, reimplemented the workaround
 in a manageable way]
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: zhengyan

Documentation/arm64/silicon-errata.rst

@@ -214,3 +214,7 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | Fujitsu        | A64FX           | E#010001        | FUJITSU_ERRATUM_010001      |
 +----------------+-----------------+-----------------+-----------------------------+
+
++----------------+-----------------+-----------------+-----------------------------+
+| ASR            | ASR8601         | #8601001        | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+

drivers/irqchip/irq-gic-v3.c

@@ -40,6 +40,7 @@
 #define FLAGS_WORKAROUND_GICR_WAKER_MSM8996	(1ULL << 0)
 #define FLAGS_WORKAROUND_CAVIUM_ERRATUM_38539	(1ULL << 1)
 #define FLAGS_WORKAROUND_MTK_GICR_SAVE		(1ULL << 2)
+#define FLAGS_WORKAROUND_ASR_ERRATUM_8601001	(1ULL << 3)
 
 #define GIC_IRQ_TYPE_PARTITION	(GIC_IRQ_TYPE_LPI + 1)
 
@@ -661,6 +662,11 @@ 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  |
@@ -1801,12 +1807,26 @@ 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",
 		.compatible = "qcom,msm8996-gic-v3",
 		.init	= gic_enable_quirk_msm8996,
 	},
+	{
+		.desc	= "GICv3: ASR erratum 8601001",
+		.compatible = "asr,asr8601-gic-v3",
+		.init	= gic_enable_quirk_asr8601,
+	},
 	{
 		.desc	= "GICv3: Mediatek Chromebook GICR save problem",
 		.property = "mediatek,broken-save-restore-fw",