Re: [PATCH v2] irqchip/gic-v3-its: Add workaround for ThunderX2 erratum #174

[Ganapatrao Kulkarni]

On Fri, Jan 19, 2018 at 5:53 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
> On 18/01/18 05:28, Ganapatrao Kulkarni wrote:
>> This erratum is observed on the ThunderX2 GICv3 ITS. When a
>> MOVI command is used to change affinity of a LPI to a collection/cpu
>> on another node, the LPI is not delivered to the cpu.
>> An additional INV command is required after the MOVI to deliver
>> the LPI to the new destination.
>>
>> If we add INV after MOVI, there is a chance that we lose LPIs which
>> are raised when the affinity is changed. So for now, adding workaround fix
>> to disable inter node affinity change.
>>
>> Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@xxxxxxxxxx>
>> ---
>>
>> v2: Added workaround to avoid inter node affinity change.
>>
>> v1: Initial patch
>>
>>  Documentation/arm64/silicon-errata.txt |  1 +
>>  arch/arm64/Kconfig                     | 10 ++++++++++
>>  drivers/irqchip/irq-gic-v3-its.c       | 21 ++++++++++++++++++++-
>>  3 files changed, 31 insertions(+), 1 deletion(-)
>>
>> 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..0dbf3bd 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -461,6 +461,16 @@ config ARM64_ERRATUM_843419
>>
>>         If unsure, say Y.
>>
>> +config CAVIUM_ERRATUM_174
>> +     bool "Cavium ThunderX2 erratum 174"
>> +     default y
>> +     help
>> +       Cavium ThunderX2 dual socket systems may loose interrupts
>> +       on affinity change to a cpu on other node.
>> +       This workaround fix avoids inter node affinity change.
>> +
>> +       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..b0cb528 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)
>
> Instead of inventing a new flag, please rename the existing one to
> ITS_FLAG_WORKAROUND_RESTRICT_NODE_AFFINITY (or something similar). There
> is really no need to have two flags that do the exact same thing,

#23144 is used to restrict ITS to collection mapping too,
where as 174 is only restricts cross node affinity.
Having said that, Since we are restricting affinity in #174,
i see there is no use of having ITS to other node collection mapping.
There should not be any issue if we club flag. I will post this change
in next version.

>
>>
>>  #define RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING  (1 << 0)
>>
>> @@ -1102,7 +1103,8 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
>>               return -EINVAL;
>>
>>         /* lpi cannot be routed to a redistributor that is on a foreign node */
>> -     if (its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) {
>> +     if (its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144 ||
>> +                     its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_174) {
>>               if (its_dev->its->numa_node >= 0) {
>>                       cpu_mask = cpumask_of_node(its_dev->its->numa_node);
>>                       if (!cpumask_intersects(mask_val, cpu_mask))
>> @@ -2904,6 +2906,15 @@ 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 +3042,14 @@ 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 */
>> +             .mask   = 0xffffffff,
>> +             .init   = its_enable_quirk_cavium_174,
>> +     },
>> +#endif
>>       {
>>       }
>>  };
>>
>
> Thanks,
>
>         M.
> --
> Jazz is not dead. It just smells funny...

thanks
Ganapat