On 9.06.2023 07:52, Parikshit Pareek wrote:
> Introduce support to detect the interconnect, and set its bandwidth.
> For certain targets, we need to set the bandwidth of interconnect,
> connecting smmu to memory. This is accessed during memory mapped IO
> access to smmu registers, and during page tables walks.
> 
> Reported-by: Eric Chanudet <echanude@redhat.com>
> Signed-off-by: Parikshit Pareek <quic_ppareek@quicinc.com>
> ---
Quite recently, I've been toying with this too.. I coded it in
a way that allows it to be reused by other impls and uses OPP APIs.
Please take a look at the attached patch.

Konrad
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index c71afda79d64..6961d564869b 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -8,6 +8,7 @@
>  #include <linux/delay.h>
>  #include <linux/of_device.h>
>  #include <linux/firmware/qcom/qcom_scm.h>
> +#include <linux/interconnect.h>
>  
>  #include "arm-smmu.h"
>  #include "arm-smmu-qcom.h"
> @@ -549,6 +550,8 @@ struct arm_smmu_device *qcom_smmu_impl_init(struct arm_smmu_device *smmu)
>  {
>  	const struct device_node *np = smmu->dev->of_node;
>  	const struct of_device_id *match;
> +	struct icc_path *icc_path;
> +	int ret, icc_bw;
>  
>  #ifdef CONFIG_ACPI
>  	if (np == NULL) {
> @@ -558,6 +561,19 @@ struct arm_smmu_device *qcom_smmu_impl_init(struct arm_smmu_device *smmu)
>  	}
>  #endif
>  
> +	icc_path = devm_of_icc_get(smmu->dev, "tbu_mc");
> +	if (IS_ERR(icc_path))
> +		return (struct arm_smmu_device *)icc_path;
> +
> +	ret = of_property_read_u32(np, "icc_bw", &icc_bw);
> +
> +	/*if interconnect exists, check for the  bandwidth value*/
> +	if (icc_path && !ret) {
> +		ret = icc_set_bw(icc_path, 0, MBps_to_icc(icc_bw));
> +		if (ret)
> +			return ERR_PTR(ret);
> +	}
> +
>  	match = of_match_node(qcom_smmu_impl_of_match, np);
>  	if (match)
>  		return qcom_smmu_create(smmu, match->data);