Re: [PATCH v9 3/3] iommu/arm-smmu-v3: Add workaround for Cavium ThunderX2 erratum #126

Will Deacon
2017-06-22T18:22:16Z

Hi Geetha,

On Thu, Jun 22, 2017 at 05:35:38PM +0530, Geetha sowjanya wrote:
> From: Geetha Sowjanya <geethasowjanya.akula@cavium.com>
>
> Cavium ThunderX2 SMMU doesn't support MSI and also doesn't have unique irq
> lines for gerror, eventq and cmdq-sync.
>
> New named irq "combined" is set as a errata workaround, which allows to
> share the irq line by register single irq handler for all the interrupts.
>
> Signed-off-by: Geetha sowjanya <gakula@caviumnetworks.com>
> ---
> Documentation/arm64/silicon-errata.txt | 1 +
> .../devicetree/bindings/iommu/arm,smmu-v3.txt | 1 +
> drivers/acpi/arm64/iort.c | 54 +++++++----
> drivers/iommu/arm-smmu-v3.c | 105 +++++++++++++++-----
> 4 files changed, 116 insertions(+), 45 deletions(-)

Thanks, this looks much better. Two things to change below, and I'd like to
see Lorenzo ack the iort changes.

> diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
> index 4693a32..42422f6 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 SMMUv2 | #27704 | N/A |
> | Cavium | ThunderX2 SMMUv3| #74 | N/A |
> +| Cavium | ThunderX2 SMMUv3| #126 | N/A |
> | | | | |
> | Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 |
> | | | | |
> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt
> index 6ecc48c..a5a1ca4 100644
> --- a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt
> @@ -26,6 +26,7 @@ the PCIe specification.
> * "priq" - PRI Queue not empty
> * "cmdq-sync" - CMD_SYNC complete
> * "gerror" - Global Error activated
> + * "combined" - Handles above all 4 interrupts.

Please make it clear that:

* The combined interrupt is optional, and should only be provided if
the hardware supports just a single, combined interrupt line.

* If provided, then the combined interrupt will be used in preference
to any others.

> - #iommu-cells : See the generic IOMMU binding described in
> devicetree/bindings/pci/pci-iommu.txt
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index c166f3e..43e1f13 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -828,6 +828,18 @@ static int __init arm_smmu_v3_count_resources(struct acpi_iort_node *node)
> return num_res;
> }
>
> +static bool arm_smmu_v3_is_combined_irq(struct acpi_iort_smmu_v3 *smmu)
> +{
> + /*
> + * Cavium ThunderX2 implementation doesn't not support unique
> + * irq line. Use single irq line for all the SMMUv3 interrupts.
> + */
> + if (smmu->model == ACPI_IORT_SMMU_V3_CAVIUM_CN99XX)
> + return true;
> +
> + return false;
> +}
> +
> static unsigned long arm_smmu_v3_resource_size(struct acpi_iort_smmu_v3 *smmu)
> {
> /*
> @@ -855,26 +867,32 @@ static void __init arm_smmu_v3_init_resources(struct resource *res,
> res[num_res].flags = IORESOURCE_MEM;
>
> num_res++;
> -
> - if (smmu->event_gsiv)
> - acpi_iort_register_irq(smmu->event_gsiv, "eventq",
> - ACPI_EDGE_SENSITIVE,
> - &res[num_res++]);
> -
> - if (smmu->pri_gsiv)
> - acpi_iort_register_irq(smmu->pri_gsiv, "priq",
> - ACPI_EDGE_SENSITIVE,
> - &res[num_res++]);
> -
> - if (smmu->gerr_gsiv)
> - acpi_iort_register_irq(smmu->gerr_gsiv, "gerror",
> - ACPI_EDGE_SENSITIVE,
> - &res[num_res++]);
> -
> - if (smmu->sync_gsiv)
> - acpi_iort_register_irq(smmu->sync_gsiv, "cmdq-sync",
> + if (arm_smmu_v3_is_combined_irq(smmu))
> + acpi_iort_register_irq(smmu->event_gsiv, "combined",
> ACPI_EDGE_SENSITIVE,
> &res[num_res++]);
> + else {
> +
> + if (smmu->event_gsiv)
> + acpi_iort_register_irq(smmu->event_gsiv, "eventq",
> + ACPI_EDGE_SENSITIVE,
> + &res[num_res++]);
> +
> + if (smmu->pri_gsiv)
> + acpi_iort_register_irq(smmu->pri_gsiv, "priq",
> + ACPI_EDGE_SENSITIVE,
> + &res[num_res++]);
> +
> + if (smmu->gerr_gsiv)
> + acpi_iort_register_irq(smmu->gerr_gsiv, "gerror",
> + ACPI_EDGE_SENSITIVE,
> + &res[num_res++]);
> +
> + if (smmu->sync_gsiv)
> + acpi_iort_register_irq(smmu->sync_gsiv, "cmdq-sync",
> + ACPI_EDGE_SENSITIVE,
> + &res[num_res++]);
> + }
> }
>
> static bool __init arm_smmu_v3_is_coherent(struct acpi_iort_node *node)
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 2dea4a9..0f83f7d 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -605,6 +605,7 @@ struct arm_smmu_device {
> struct arm_smmu_priq priq;
>
> int gerr_irq;
> + int combined_irq;
>
> unsigned long ias; /* IPA */
> unsigned long oas; /* PA */
> @@ -1314,6 +1315,29 @@ static irqreturn_t arm_smmu_gerror_handler(int irq, void *dev)
> return IRQ_HANDLED;
> }
>
> +static irqreturn_t arm_smmu_combined_irq_thread(int irq, void *dev)
> +{
> + struct arm_smmu_device *smmu = dev;
> +
> + arm_smmu_evtq_thread(irq, dev);
> + if (smmu->features & ARM_SMMU_FEAT_PRI)
> + arm_smmu_priq_thread(irq, dev);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t arm_smmu_combined_irq_handler(int irq, void *dev)
> +{
> + irqreturn_t ret;
> +
> + ret = arm_smmu_gerror_handler(irq, dev);
> + if (ret == IRQ_NONE) {

I don't think you can play that trick if the irq is an edge-triggered
interrupt, since you could lose an interrupt that fired whilst we were
in the handler.

The easiest thing is to always run the gerror and cmdq_sync handlers, and
then always return IRQ_WAKE_THREAD.

Will