Re: [PATCH v6 2/2] iommu/riscv: create a auxiliary device for HPM

[Yicong Yang]

On 8/24/26 10:20 AM, Zong Li wrote:
> Create an auxiliary device for HPM when the IOMMU supports a
> hardware performance monitor.
> 
> Tested-by: Chen Pei <cp0613@xxxxxxxxxxxxxxxxx>
> Tested-by: Fangyu Yu <fangyu.yu@xxxxxxxxxxxxxxxxx>
> Reviewed-by: Guo Ren <guoren@xxxxxxxxxx>
> Suggested-by: Samuel Holland <samuel.holland@xxxxxxxxxx>
> Signed-off-by: Zong Li <zong.li@xxxxxxxxxx>

Reviewed-by: Yicong Yang <yang.yicong@xxxxxxxxxxxxx>

> ---
>  drivers/iommu/riscv/Kconfig |  1 +
>  drivers/iommu/riscv/iommu.c | 37 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 38 insertions(+)
> 
> diff --git a/drivers/iommu/riscv/Kconfig b/drivers/iommu/riscv/Kconfig
> index b86e5ab94183..8025bf0fb67f 100644
> --- a/drivers/iommu/riscv/Kconfig
> +++ b/drivers/iommu/riscv/Kconfig
> @@ -10,6 +10,7 @@ config RISCV_IOMMU
>  	select GENERIC_PT
>  	select IOMMU_PT
>  	select IOMMU_PT_RISCV64
> +	select AUXILIARY_BUS
>  	help
>  	  Support for implementations of the RISC-V IOMMU architecture that
>  	  complements the RISC-V MMU capabilities, providing similar address
> diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
> index cec3ddd7ab10..7f619971bb70 100644
> --- a/drivers/iommu/riscv/iommu.c
> +++ b/drivers/iommu/riscv/iommu.c
> @@ -14,6 +14,7 @@
>  
>  #include <linux/acpi.h>
>  #include <linux/acpi_rimt.h>
> +#include <linux/auxiliary_bus.h>
>  #include <linux/compiler.h>
>  #include <linux/crash_dump.h>
>  #include <linux/init.h>
> @@ -48,6 +49,9 @@
>  static DEFINE_IDA(riscv_iommu_pscids);
>  #define RISCV_IOMMU_MAX_PSCID		(BIT(20) - 1)
>  
> +/* IOMMU PMU auxiliary device id allocation namespace. */
> +static DEFINE_IDA(riscv_iommu_pmu_ida);
> +
>  /* Device resource-managed allocations */
>  struct riscv_iommu_devres {
>  	void *addr;
> @@ -565,6 +569,36 @@ static irqreturn_t riscv_iommu_fltq_process(int irq, void *data)
>  	return IRQ_HANDLED;
>  }
>  
> +/*
> + * IOMMU Hardware performance monitor
> + */
> +static void riscv_iommu_pmu_id_free(void *data)
> +{
> +	ida_free(&riscv_iommu_pmu_ida, (unsigned long)data);
> +}
> +
> +static int riscv_iommu_hpm_enable(struct riscv_iommu_device *iommu)
> +{
> +	struct auxiliary_device *auxdev;
> +	int id, ret;
> +
> +	id = ida_alloc(&riscv_iommu_pmu_ida, GFP_KERNEL);
> +	if (id < 0)
> +		return id;
> +
> +	ret = devm_add_action_or_reset(iommu->dev, riscv_iommu_pmu_id_free,
> +				       (void *)(unsigned long)id);
> +	if (ret)
> +		return ret;
> +
> +	auxdev = __devm_auxiliary_device_create(iommu->dev, "riscv-iommu",
> +						"pmu", iommu, id);
> +	if (!auxdev)
> +		return -ENODEV;
> +
> +	return 0;
> +}
> +
>  /* Lookup and initialize device context info structure. */
>  static struct riscv_iommu_dc *riscv_iommu_get_dc(struct riscv_iommu_device *iommu,
>  						 unsigned int devid)
> @@ -1613,6 +1647,9 @@ int riscv_iommu_init(struct riscv_iommu_device *iommu)
>  		goto err_remove_sysfs;
>  	}
>  
> +	if (iommu->caps & RISCV_IOMMU_CAPABILITIES_HPM)
> +		riscv_iommu_hpm_enable(iommu);
> +
>  	return 0;
>  
>  err_remove_sysfs: