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SubjectRe: [PATCH] irqchip/gic-v3-its: Add workaround for ThunderX2 erratum #174
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On 03/01/18 06:32, Ganapatrao Kulkarni wrote:
> When an interrupt is moved across node collections on ThunderX2

node collections?

> multi Socket platform, an interrupt stops routed to new collection
> and results in loss of interrupts.
>
> Adding workaround to issue INV after MOVI for cross-node collection
> move to flush out the cached entry.
>
> Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@cavium.com>
> ---
> Documentation/arm64/silicon-errata.txt | 1 +
> arch/arm64/Kconfig | 11 +++++++++++
> drivers/irqchip/irq-gic-v3-its.c | 24 ++++++++++++++++++++++++
> 3 files changed, 36 insertions(+)
>
> diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
> index fc1c884..fb27cb5 100644
> --- a/Documentation/arm64/silicon-errata.txt
> +++ b/Documentation/arm64/silicon-errata.txt
> @@ -63,6 +63,7 @@ stable kernels.
> | Cavium | ThunderX Core | #27456 | CAVIUM_ERRATUM_27456 |
> | Cavium | ThunderX Core | #30115 | CAVIUM_ERRATUM_30115 |
> | Cavium | ThunderX SMMUv2 | #27704 | N/A |
> +| Cavium | ThunderX2 ITS | #174 | CAVIUM_ERRATUM_174 |
> | Cavium | ThunderX2 SMMUv3| #74 | N/A |
> | Cavium | ThunderX2 SMMUv3| #126 | N/A |
> | | | | |
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index c9a7e9e..71a7e30 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -461,6 +461,17 @@ config ARM64_ERRATUM_843419
>
> If unsure, say Y.
>
> +config CAVIUM_ERRATUM_174
> + bool "Cavium ThunderX2 erratum 174"
> + depends on NUMA

Why? This system will be affected no matter whether NUMA is selected or not.

> + default y
> + help
> + LPI stops routed to redistributors after inter node collection
> + move in ITS. Enable workaround to invalidate ITS entry after
> + inter-node collection move.

That's a very terse description. Nobody knows what an LPI, a
redistributor or a collection is. Please explain what the erratum is in
layman's terms (Cavium ThunderX2 systems may loose interrupts on
affinity change) so that people understand whether or not they are affected.

> +
> + If unsure, say Y.
> +
> config CAVIUM_ERRATUM_22375
> bool "Cavium erratum 22375, 24313"
> default y
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 06f025f..d8b9c96 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -46,6 +46,7 @@
> #define ITS_FLAGS_CMDQ_NEEDS_FLUSHING (1ULL << 0)
> #define ITS_FLAGS_WORKAROUND_CAVIUM_22375 (1ULL << 1)
> #define ITS_FLAGS_WORKAROUND_CAVIUM_23144 (1ULL << 2)
> +#define ITS_FLAGS_WORKAROUND_CAVIUM_174 (1ULL << 3)
>
> #define RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING (1 << 0)
>
> @@ -1119,6 +1120,12 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
> if (cpu != its_dev->event_map.col_map[id]) {
> target_col = &its_dev->its->collections[cpu];
> its_send_movi(its_dev, target_col, id);
> + if (its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_174) {
> + /* Issue INV for cross node collection move. */
> + if (cpu_to_node(cpu) !=
> + cpu_to_node(its_dev->event_map.col_map[id]))
> + its_send_inv(its_dev, id);
> + }

What happens if an interrupt happens after the MOV, but before the INV?

> its_dev->event_map.col_map[id] = cpu;
> irq_data_update_effective_affinity(d, cpumask_of(cpu));
> }
> @@ -2904,6 +2911,15 @@ static int its_force_quiescent(void __iomem *base)
> }
> }
>
> +static bool __maybe_unused its_enable_quirk_cavium_174(void *data)
> +{
> + struct its_node *its = data;
> +
> + its->flags |= ITS_FLAGS_WORKAROUND_CAVIUM_174;
> +
> + return true;
> +}
> +
> static bool __maybe_unused its_enable_quirk_cavium_22375(void *data)
> {
> struct its_node *its = data;
> @@ -3031,6 +3047,14 @@ static const struct gic_quirk its_quirks[] = {
> .init = its_enable_quirk_hip07_161600802,
> },
> #endif
> +#ifdef CONFIG_CAVIUM_ERRATUM_174
> + {
> + .desc = "ITS: Cavium ThunderX2 erratum 174",
> + .iidr = 0x13f, /* ThunderX2 pass A1/A2/B0 */

Do all 3 revisions have the same IIDR?

> + .mask = 0xffffffff,
> + .init = its_enable_quirk_cavium_174,
> + },
> +#endif
> {
> }
> };
>

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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