Re: [PATCH v7 2/3] iommu/arm-smmu-v3: Add workaround for Cavium ThunderX2 erratum #74

[Robin Murphy <robin.murphy@arm.com>]

On 30/05/17 13:03, Geetha sowjanya wrote:
> From: Linu Cherian <linu.cherian@cavium.com>
> 
> Cavium ThunderX2 SMMU implementation doesn't support page 1 register space
> and PAGE0_REGS_ONLY option is enabled as an errata workaround.
> This option when turned on, replaces all page 1 offsets used for
> EVTQ_PROD/CONS, PRIQ_PROD/CONS register access with page 0 offsets.
> 
> SMMU resource size checks are now based on SMMU option PAGE0_REGS_ONLY,
> since resource size can be either 64k/128k.
> For this, arm_smmu_device_dt_probe/acpi_probe has been moved before
> platform_get_resource call, so that SMMU options are set beforehand.
> 
> Signed-off-by: Linu Cherian <linu.cherian@cavium.com>
> Signed-off-by: Geetha Sowjanya <geethasowjanya.akula@cavium.com>
> ---
>  Documentation/arm64/silicon-errata.txt             |    1 +
>  .../devicetree/bindings/iommu/arm,smmu-v3.txt      |    6 ++
>  drivers/iommu/arm-smmu-v3.c                        |   64 +++++++++++++++-----
>  3 files changed, 56 insertions(+), 15 deletions(-)
> 
> diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
> index 10f2ddd..4693a32 100644
> --- a/Documentation/arm64/silicon-errata.txt
> +++ b/Documentation/arm64/silicon-errata.txt
> @@ -62,6 +62,7 @@ stable kernels.
>  | Cavium         | ThunderX GICv3  | #23154          | CAVIUM_ERRATUM_23154        |
>  | Cavium         | ThunderX Core   | #27456          | CAVIUM_ERRATUM_27456        |
>  | Cavium         | ThunderX SMMUv2 | #27704          | N/A                         |
> +| Cavium         | ThunderX2 SMMUv3| #74             | 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 be57550..607e270 100644
> --- a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt
> @@ -49,6 +49,12 @@ the PCIe specification.
>  - hisilicon,broken-prefetch-cmd
>                      : Avoid sending CMD_PREFETCH_* commands to the SMMU.
>  
> +- cavium,cn9900-broken-page1-regspace
> +                    : Replaces all page 1 offsets used for EVTQ_PROD/CONS,
> +						PRIQ_PROD/CONS register access with page 0 offsets.
> +						Set for Caviun ThunderX2 silicon that doesn't support
> +						SMMU page1 register space.

The indentation's a bit funky here - the rest of this file is actually
indented with spaces, but either way it's clear your editor isn't set to
8-space tabs ;)

> +
>  ** Example
>  
>          smmu@2b400000 {
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 380969a..4e80205 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -412,6 +412,9 @@
>  #define MSI_IOVA_BASE			0x8000000
>  #define MSI_IOVA_LENGTH			0x100000
>  
> +#define ARM_SMMU_PAGE0_REGS_ONLY(smmu)		\
> +	((smmu)->options & ARM_SMMU_OPT_PAGE0_REGS_ONLY)

At the two places we use this macro, frankly I think it would be clearer
to just reference smmu->options directly, as we currently do for
SKIP_PREFETCH. The abstraction also adds more lines than it saves...

> +
>  static bool disable_bypass;
>  module_param_named(disable_bypass, disable_bypass, bool, S_IRUGO);
>  MODULE_PARM_DESC(disable_bypass,
> @@ -597,6 +600,7 @@ struct arm_smmu_device {
>  	u32				features;
>  
>  #define ARM_SMMU_OPT_SKIP_PREFETCH	(1 << 0)
> +#define ARM_SMMU_OPT_PAGE0_REGS_ONLY    (1 << 1)

Whitespace again, although this time it's spaces where there should be a
tab.

>  	u32				options;
>  
>  	struct arm_smmu_cmdq		cmdq;
> @@ -663,9 +667,19 @@ struct arm_smmu_option_prop {
>  
>  static struct arm_smmu_option_prop arm_smmu_options[] = {
>  	{ ARM_SMMU_OPT_SKIP_PREFETCH, "hisilicon,broken-prefetch-cmd" },
> +	{ ARM_SMMU_OPT_PAGE0_REGS_ONLY, "cavium,cn9900-broken-page1-regspace"},
>  	{ 0, NULL},
>  };
>  
> +static inline void __iomem *arm_smmu_page1_fixup(unsigned long offset,
> +						 struct arm_smmu_device *smmu)
> +{
> +	if (offset > SZ_64K && ARM_SMMU_PAGE0_REGS_ONLY(smmu))
> +		offset -= SZ_64K;
> +
> +	return smmu->base + offset;
> +}
> +
>  static struct arm_smmu_domain *to_smmu_domain(struct iommu_domain *dom)
>  {
>  	return container_of(dom, struct arm_smmu_domain, domain);
> @@ -1961,8 +1975,8 @@ static int arm_smmu_init_one_queue(struct arm_smmu_device *smmu,
>  		return -ENOMEM;
>  	}
>  
> -	q->prod_reg	= smmu->base + prod_off;
> -	q->cons_reg	= smmu->base + cons_off;
> +	q->prod_reg	= arm_smmu_page1_fixup(prod_off, smmu);
> +	q->cons_reg	= arm_smmu_page1_fixup(cons_off, smmu);
>  	q->ent_dwords	= dwords;
>  
>  	q->q_base  = Q_BASE_RWA;
> @@ -2363,8 +2377,10 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
>  
>  	/* Event queue */
>  	writeq_relaxed(smmu->evtq.q.q_base, smmu->base + ARM_SMMU_EVTQ_BASE);
> -	writel_relaxed(smmu->evtq.q.prod, smmu->base + ARM_SMMU_EVTQ_PROD);
> -	writel_relaxed(smmu->evtq.q.cons, smmu->base + ARM_SMMU_EVTQ_CONS);
> +	writel_relaxed(smmu->evtq.q.prod,
> +		       arm_smmu_page1_fixup(ARM_SMMU_EVTQ_PROD, smmu));
> +	writel_relaxed(smmu->evtq.q.cons,
> +		       arm_smmu_page1_fixup(ARM_SMMU_EVTQ_CONS, smmu));
>  
>  	enables |= CR0_EVTQEN;
>  	ret = arm_smmu_write_reg_sync(smmu, enables, ARM_SMMU_CR0,
> @@ -2379,9 +2395,9 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
>  		writeq_relaxed(smmu->priq.q.q_base,
>  			       smmu->base + ARM_SMMU_PRIQ_BASE);
>  		writel_relaxed(smmu->priq.q.prod,
> -			       smmu->base + ARM_SMMU_PRIQ_PROD);
> +			       arm_smmu_page1_fixup(ARM_SMMU_PRIQ_PROD, smmu));
>  		writel_relaxed(smmu->priq.q.cons,
> -			       smmu->base + ARM_SMMU_PRIQ_CONS);
> +			       arm_smmu_page1_fixup(ARM_SMMU_PRIQ_CONS, smmu));
>  
>  		enables |= CR0_PRIQEN;
>  		ret = arm_smmu_write_reg_sync(smmu, enables, ARM_SMMU_CR0,
> @@ -2605,6 +2621,14 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
>  }
>  
>  #ifdef CONFIG_ACPI
> +static void acpi_smmu_get_options(u32 model, struct arm_smmu_device *smmu)
> +{
> +	if (model == ACPI_IORT_SMMU_CAVIUM_CN99XX)
> +		smmu->options |= ARM_SMMU_OPT_PAGE0_REGS_ONLY;
> +
> +	dev_notice(smmu->dev, "option mask 0x%x\n", smmu->options);
> +}
> +
>  static int arm_smmu_device_acpi_probe(struct platform_device *pdev,
>  				      struct arm_smmu_device *smmu)
>  {
> @@ -2617,6 +2641,8 @@ static int arm_smmu_device_acpi_probe(struct platform_device *pdev,
>  	/* Retrieve SMMUv3 specific data */
>  	iort_smmu = (struct acpi_iort_smmu_v3 *)node->node_data;
>  
> +	acpi_smmu_get_options(iort_smmu->model, smmu);
> +
>  	if (iort_smmu->flags & ACPI_IORT_SMMU_V3_COHACC_OVERRIDE)
>  		smmu->features |= ARM_SMMU_FEAT_COHERENCY;
>  
> @@ -2652,6 +2678,14 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev,
>  	return ret;
>  }
>  
> +static unsigned long arm_smmu_resource_size(struct arm_smmu_device *smmu)
> +{
> +	if (ARM_SMMU_PAGE0_REGS_ONLY(smmu))
> +		return SZ_64K;
> +	else
> +		return SZ_128K;
> +}
> +
>  static int arm_smmu_device_probe(struct platform_device *pdev)
>  {
>  	int irq, ret;
> @@ -2668,9 +2702,17 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>  	}
>  	smmu->dev = dev;
>  
> +	if (dev->of_node) {
> +		ret = arm_smmu_device_dt_probe(pdev, smmu);
> +	} else {
> +		ret = arm_smmu_device_acpi_probe(pdev, smmu);
> +		if (ret == -ENODEV)
> +			return ret;
> +	}
> +
>  	/* Base address */
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> -	if (resource_size(res) + 1 < SZ_128K) {
> +	if (resource_size(res) + 1 < arm_smmu_resource_size(smmu)) {
>  		dev_err(dev, "MMIO region too small (%pr)\n", res);
>  		return -EINVAL;
>  	}
> @@ -2697,14 +2739,6 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>  	if (irq > 0)
>  		smmu->gerr_irq = irq;
>  
> -	if (dev->of_node) {
> -		ret = arm_smmu_device_dt_probe(pdev, smmu);
> -	} else {
> -		ret = arm_smmu_device_acpi_probe(pdev, smmu);
> -		if (ret == -ENODEV)
> -			return ret;
> -	}
> -
>  	/* Set bypass mode according to firmware probing result */
>  	bypass = !!ret;

The bypass setting is directly related to the {dt,acpi}_probe logic, so
should move along with it. I can see that this ends up still working
because none of the interim code touches ret, but it does make things
unnecessarily hard to follow.

Robin.