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SubjectRe: [PATCH v8 1/3] iommu/arm-smmu: add NVIDIA implementation for dual ARM MMU-500 usage
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On 30/06/2020 01:10, Krishna Reddy wrote:
> NVIDIA's Tegra194 SoC uses two ARM MMU-500s together to interleave
> IOVA accesses across them.
> Add NVIDIA implementation for dual ARM MMU-500s and add new compatible
> string for Tegra194 SoC SMMU topology.

There is no description here of the 3rd SMMU that you mention below.
I think that we should describe the full picture here.

> Signed-off-by: Krishna Reddy <vdumpa@nvidia.com>
> ---
> MAINTAINERS | 2 +
> drivers/iommu/Makefile | 2 +-
> drivers/iommu/arm-smmu-impl.c | 3 +
> drivers/iommu/arm-smmu-nvidia.c | 196 ++++++++++++++++++++++++++++++++
> drivers/iommu/arm-smmu.h | 1 +
> 5 files changed, 203 insertions(+), 1 deletion(-)
> create mode 100644 drivers/iommu/arm-smmu-nvidia.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 7b5ffd646c6b9..64c37dbdd4426 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -16808,8 +16808,10 @@ F: drivers/i2c/busses/i2c-tegra.c
>
> TEGRA IOMMU DRIVERS
> M: Thierry Reding <thierry.reding@gmail.com>
> +R: Krishna Reddy <vdumpa@nvidia.com>
> L: linux-tegra@vger.kernel.org
> S: Supported
> +F: drivers/iommu/arm-smmu-nvidia.c
> F: drivers/iommu/tegra*
>
> TEGRA KBC DRIVER
> diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
> index 342190196dfb0..2b8203db73ec3 100644
> --- a/drivers/iommu/Makefile
> +++ b/drivers/iommu/Makefile
> @@ -15,7 +15,7 @@ obj-$(CONFIG_AMD_IOMMU) += amd/iommu.o amd/init.o amd/quirks.o
> obj-$(CONFIG_AMD_IOMMU_DEBUGFS) += amd/debugfs.o
> obj-$(CONFIG_AMD_IOMMU_V2) += amd/iommu_v2.o
> obj-$(CONFIG_ARM_SMMU) += arm_smmu.o
> -arm_smmu-objs += arm-smmu.o arm-smmu-impl.o arm-smmu-qcom.o
> +arm_smmu-objs += arm-smmu.o arm-smmu-impl.o arm-smmu-nvidia.o arm-smmu-qcom.o
> obj-$(CONFIG_ARM_SMMU_V3) += arm-smmu-v3.o
> obj-$(CONFIG_DMAR_TABLE) += intel/dmar.o
> obj-$(CONFIG_INTEL_IOMMU) += intel/iommu.o intel/pasid.o
> diff --git a/drivers/iommu/arm-smmu-impl.c b/drivers/iommu/arm-smmu-impl.c
> index c75b9d957b702..70f7318017617 100644
> --- a/drivers/iommu/arm-smmu-impl.c
> +++ b/drivers/iommu/arm-smmu-impl.c
> @@ -171,6 +171,9 @@ struct arm_smmu_device *arm_smmu_impl_init(struct arm_smmu_device *smmu)
> if (of_property_read_bool(np, "calxeda,smmu-secure-config-access"))
> smmu->impl = &calxeda_impl;
>
> + if (of_device_is_compatible(smmu->dev->of_node, "nvidia,tegra194-smmu"))
> + return nvidia_smmu_impl_init(smmu);
> +
> if (of_device_is_compatible(np, "qcom,sdm845-smmu-500") ||
> of_device_is_compatible(np, "qcom,sc7180-smmu-500"))
> return qcom_smmu_impl_init(smmu);
> diff --git a/drivers/iommu/arm-smmu-nvidia.c b/drivers/iommu/arm-smmu-nvidia.c
> new file mode 100644
> index 0000000000000..1124f0ac1823a
> --- /dev/null
> +++ b/drivers/iommu/arm-smmu-nvidia.c
> @@ -0,0 +1,196 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// NVIDIA ARM SMMU v2 implementation quirks
> +// Copyright (C) 2019-2020 NVIDIA CORPORATION. All rights reserved.
> +
> +#include <linux/bitfield.h>
> +#include <linux/delay.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +
> +#include "arm-smmu.h"
> +
> +/*
> + * Tegra194 has three ARM MMU-500 Instances.
> + * Two of them are used together for interleaved IOVA accesses and
> + * used by non-isochronous HW devices for SMMU translations.
> + * Third one is used for SMMU translations from isochronous HW devices.
> + * It is possible to use this implementation to program either
> + * all three or two of the instances identically as desired through
> + * DT node.
> + *
> + * Programming all the three instances identically comes with redundant TLB
> + * invalidations as all three never need to be TLB invalidated for a HW device.
> + *
> + * When Linux kernel supports multiple SMMU devices, the SMMU device used for
> + * isochornous HW devices should be added as a separate ARM MMU-500 device
> + * in DT and be programmed independently for efficient TLB invalidates.
> + */
> +#define MAX_SMMU_INSTANCES 3
> +
> +#define TLB_LOOP_TIMEOUT_IN_US 1000000 /* 1s! */
> +#define TLB_SPIN_COUNT 10
> +
> +struct nvidia_smmu {
> + struct arm_smmu_device smmu;
> + unsigned int num_inst;
> + void __iomem *bases[MAX_SMMU_INSTANCES];
> +};
> +
> +static inline struct nvidia_smmu *to_nvidia_smmu(struct arm_smmu_device *smmu)
> +{
> + return container_of(smmu, struct nvidia_smmu, smmu);
> +}
> +
> +static inline void __iomem *nvidia_smmu_page(struct arm_smmu_device *smmu,
> + unsigned int inst, int page)

If you run checkpatch --strict on these you will get a lot of ...

CHECK: Alignment should match open parenthesis
#116: FILE: drivers/iommu/arm-smmu-nvidia.c:46:
+static inline void __iomem *nvidia_smmu_page(struct arm_smmu_device *smmu,
+ unsigned int inst, int page)

We should fix these.

> +{
> + struct nvidia_smmu *nvidia_smmu = to_nvidia_smmu(smmu);
> +
> + if (!nvidia_smmu->bases[0])
> + nvidia_smmu->bases[0] = smmu->base;
> +
> + return nvidia_smmu->bases[inst] + (page << smmu->pgshift);
> +}
> +
> +static u32 nvidia_smmu_read_reg(struct arm_smmu_device *smmu,
> + int page, int offset)
> +{
> + void __iomem *reg = nvidia_smmu_page(smmu, 0, page) + offset;
> +
> + return readl_relaxed(reg);
> +}
> +
> +static void nvidia_smmu_write_reg(struct arm_smmu_device *smmu,
> + int page, int offset, u32 val)
> +{
> + unsigned int i;
> + struct nvidia_smmu *nvidia_smmu = to_nvidia_smmu(smmu);
> +
> + for (i = 0; i < nvidia_smmu->num_inst; i++) {
> + void __iomem *reg = nvidia_smmu_page(smmu, i, page) + offset;

Personally, I would declare 'reg' outside of the loop as I feel it will make
the code cleaner and easier to read.

> +
> + writel_relaxed(val, reg);
> + }
> +}
> +
> +static u64 nvidia_smmu_read_reg64(struct arm_smmu_device *smmu,
> + int page, int offset)
> +{
> + void __iomem *reg = nvidia_smmu_page(smmu, 0, page) + offset;
> +
> + return readq_relaxed(reg);
> +}
> +
> +static void nvidia_smmu_write_reg64(struct arm_smmu_device *smmu,
> + int page, int offset, u64 val)
> +{
> + unsigned int i;
> + struct nvidia_smmu *nvidia_smmu = to_nvidia_smmu(smmu);
> +
> + for (i = 0; i < nvidia_smmu->num_inst; i++) {
> + void __iomem *reg = nvidia_smmu_page(smmu, i, page) + offset;
> +
> + writeq_relaxed(val, reg);
> + }
> +}
> +
> +static void nvidia_smmu_tlb_sync(struct arm_smmu_device *smmu, int page,
> + int sync, int status)
> +{
> + unsigned int delay;
> +
> + arm_smmu_writel(smmu, page, sync, 0);
> +
> + for (delay = 1; delay < TLB_LOOP_TIMEOUT_IN_US; delay *= 2) {

So we are doubling the delay every time? Is this better than just using
the same on each loop?

> + unsigned int spin_cnt;
> +
> + for (spin_cnt = TLB_SPIN_COUNT; spin_cnt > 0; spin_cnt--) {
> + u32 val = 0;
> + unsigned int i;
> + struct nvidia_smmu *nvidia_smmu = to_nvidia_smmu(smmu);

Why not do this once at the beginning of the function?

> +
> + for (i = 0; i < nvidia_smmu->num_inst; i++) {
> + void __iomem *reg =
> + nvidia_smmu_page(smmu, i, page) + status;
> +
> + val |= readl_relaxed(reg);
> + }
> +
> + if (!(val & ARM_SMMU_sTLBGSTATUS_GSACTIVE))
> + return;
> +
> + cpu_relax();
> + }
> +
> + udelay(delay);
> + }
> +
> + dev_err_ratelimited(smmu->dev,
> + "TLB sync timed out -- SMMU may be deadlocked\n");
> +}
> +
> +static int nvidia_smmu_reset(struct arm_smmu_device *smmu)
> +{
> + unsigned int i;
> +
> + for (i = 0; i < to_nvidia_smmu(smmu)->num_inst; i++) {
> + u32 val;
> + void __iomem *reg = nvidia_smmu_page(smmu, i, ARM_SMMU_GR0) +
> + ARM_SMMU_GR0_sGFSR;

I feel that declaring variables here clutters the code.

> +
> + /* clear global FSR */
> + val = readl_relaxed(reg);
> + writel_relaxed(val, reg);
> + }
> +
> + return 0;
> +}
> +
> +static const struct arm_smmu_impl nvidia_smmu_impl = {
> + .read_reg = nvidia_smmu_read_reg,
> + .write_reg = nvidia_smmu_write_reg,
> + .read_reg64 = nvidia_smmu_read_reg64,
> + .write_reg64 = nvidia_smmu_write_reg64,
> + .reset = nvidia_smmu_reset,
> + .tlb_sync = nvidia_smmu_tlb_sync,
> +};
> +
> +struct arm_smmu_device *nvidia_smmu_impl_init(struct arm_smmu_device *smmu)
> +{
> + unsigned int i;
> + struct nvidia_smmu *nvidia_smmu;
> + struct platform_device *pdev = to_platform_device(smmu->dev);
> +
> + nvidia_smmu = devm_kzalloc(smmu->dev, sizeof(*nvidia_smmu), GFP_KERNEL);
> + if (!nvidia_smmu)
> + return ERR_PTR(-ENOMEM);
> +
> + nvidia_smmu->smmu = *smmu;
> + /* Instance 0 is ioremapped by arm-smmu.c after this function returns */
> + nvidia_smmu->num_inst = 1;
> +
> + for (i = 1; i < MAX_SMMU_INSTANCES; i++) {
> + struct resource *res;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, i);
> + if (!res)
> + break;
> +
> + nvidia_smmu->bases[i] = devm_ioremap_resource(smmu->dev, res);
> + if (IS_ERR(nvidia_smmu->bases[i]))
> + return ERR_CAST(nvidia_smmu->bases[i]);
> +
> + nvidia_smmu->num_inst++;
> + }
> +
> + nvidia_smmu->smmu.impl = &nvidia_smmu_impl;
> + /*
> + * Free the arm_smmu_device struct allocated in arm-smmu.c.
> + * Once this function returns, arm-smmu.c would use arm_smmu_device
> + * allocated as part of nvidia_smmu struct.
> + */
> + devm_kfree(smmu->dev, smmu);

Why don't we just store the pointer of the smmu struct passed to this function
in the nvidia_smmu struct and then we do not need to free this here. In other
words make ...

struct nvidia_smmu {
struct arm_smmu_device *smmu;
unsigned int num_inst;
void __iomem *bases[MAX_SMMU_INSTANCES];
};

This seems more appropriate, than copying the struct and freeing memory
allocated else-where.

> +
> + return &nvidia_smmu->smmu;
> +}
> diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
> index d172c024be618..8cf1511ed9874 100644
> --- a/drivers/iommu/arm-smmu.h
> +++ b/drivers/iommu/arm-smmu.h
> @@ -450,6 +450,7 @@ static inline void arm_smmu_writeq(struct arm_smmu_device *smmu, int page,
> arm_smmu_writeq((s), ARM_SMMU_CB((s), (n)), (o), (v))
>
> struct arm_smmu_device *arm_smmu_impl_init(struct arm_smmu_device *smmu);
> +struct arm_smmu_device *nvidia_smmu_impl_init(struct arm_smmu_device *smmu);
> struct arm_smmu_device *qcom_smmu_impl_init(struct arm_smmu_device *smmu);
>
> int arm_mmu500_reset(struct arm_smmu_device *smmu);
>

Cheers
Jon

--
nvpublic

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