Re: [PATCH v2 4/5] firmware: tegra: bpmp: Add MBWT BPMP helpers

[Mikko Perttunen <mperttunen@nvidia.com>]

On Wednesday, July 22, 2026 8:05 PM Aniruddha Rao wrote:
> Add helper functions that send MBWT requests to BPMP firmware.
> 
> The helpers implement the GET_BW and SET_BW operations.
> 
> They also provide a QUERY_ABI-based probe for command availability.
> 
> Signed-off-by: Aniruddha Rao <anrao@nvidia.com>
> ---
> Changes since v1:
> - Use generic tegra_bpmp_mbwt_*() helper names.
> - Fold the helpers into bpmp.c instead of adding a separate source file.
> - Drop SoC-specific Kconfig dependencies from the helper patch.
> - Return BPMP firmware errors directly.
> 
>  drivers/firmware/tegra/bpmp-private.h |  7 ++
>  drivers/firmware/tegra/bpmp.c         | 98 +++++++++++++++++++++++++++
>  2 files changed, 105 insertions(+)
> 
> diff --git a/drivers/firmware/tegra/bpmp-private.h b/drivers/firmware/tegra/bpmp-private.h
> index 07c3d46abb87..b3770e71020e 100644
> --- a/drivers/firmware/tegra/bpmp-private.h
> +++ b/drivers/firmware/tegra/bpmp-private.h
> @@ -26,4 +26,11 @@ struct tegra_bpmp_ops {
>  extern const struct tegra_bpmp_ops tegra186_bpmp_ops;
>  extern const struct tegra_bpmp_ops tegra210_bpmp_ops;
>  
> +bool tegra_bpmp_mbwt_cmd_is_supported(struct tegra_bpmp *bpmp,
> +				      unsigned int cmd_code);
> +int tegra_bpmp_mbwt_get(struct tegra_bpmp *bpmp, unsigned int instance,
> +			unsigned int vc_type, unsigned int *bandwidth);
> +int tegra_bpmp_mbwt_set(struct tegra_bpmp *bpmp, unsigned int instance,
> +			unsigned int vc_type, unsigned int bandwidth);
> +
>  #endif
> diff --git a/drivers/firmware/tegra/bpmp.c b/drivers/firmware/tegra/bpmp.c
> index 2dcb74a45b59..2cf8490b8b2e 100644
> --- a/drivers/firmware/tegra/bpmp.c
> +++ b/drivers/firmware/tegra/bpmp.c
> @@ -675,6 +675,104 @@ bool tegra_bpmp_mrq_is_supported(struct tegra_bpmp *bpmp, unsigned int mrq)
>  }
>  EXPORT_SYMBOL_GPL(tegra_bpmp_mrq_is_supported);
>  
> +bool tegra_bpmp_mbwt_cmd_is_supported(struct tegra_bpmp *bpmp,
> +				      unsigned int cmd_code)
> +{
> +	struct mrq_sochub_mbwt_request request = {
> +		.cmd = CMD_SOCHUB_MBWT_QUERY_ABI,
> +		.query_abi.cmd_code = cmd_code,
> +	};
> +	struct tegra_bpmp_message msg = {
> +		.mrq = MRQ_SOCHUB_MBWT,
> +		.tx = {
> +			.data = &request,
> +			.size = sizeof(request),
> +		},
> +	};
> +	int err;
> +
> +	err = tegra_bpmp_transfer(bpmp, &msg);
> +	if (err || msg.rx.ret)
> +		return false;
> +
> +	return true;
> +}
> +
> +int tegra_bpmp_mbwt_get(struct tegra_bpmp *bpmp, unsigned int instance,
> +			unsigned int vc_type, unsigned int *bandwidth)
> +{
> +	struct mrq_sochub_mbwt_request request = {
> +		.cmd = CMD_SOCHUB_MBWT_GET_BW,
> +		.get_bw = {
> +			.instance = instance,
> +			.vc_type = vc_type,
> +		},
> +	};
> +	struct mrq_sochub_mbwt_response response = {};
> +	struct tegra_bpmp_message msg = {
> +		.mrq = MRQ_SOCHUB_MBWT,
> +		.tx = {
> +			.data = &request,
> +			.size = sizeof(request),
> +		},
> +		.rx = {
> +			.data = &response,
> +			.size = sizeof(response),
> +		},
> +	};
> +	int err;
> +
> +	if (!bandwidth)
> +		return -EINVAL;
> +
> +	err = tegra_bpmp_transfer(bpmp, &msg);
> +	if (err) {
> +		dev_err(bpmp->dev, "MBWT get bandwidth transfer failed: %d\n",
> +			err);
> +		return err;
> +	}
> +
> +	if (msg.rx.ret)
> +		return msg.rx.ret;

BPMP errnos are not identical to Linux errnos. We should not mix the 
two. Same for below. Return a static error code here -- if handling 
specific BPMP error codes is really necessary, they should be returned 
in a separate out-pointer.

> +
> +	*bandwidth = response.get_bw.bw;
> +
> +	return 0;
> +}
> +
> +int tegra_bpmp_mbwt_set(struct tegra_bpmp *bpmp, unsigned int instance,
> +			unsigned int vc_type, unsigned int bandwidth)
> +{
> +	struct mrq_sochub_mbwt_request request = {
> +		.cmd = CMD_SOCHUB_MBWT_SET_BW,
> +		.set_bw = {
> +			.instance = instance,
> +			.vc_type = vc_type,
> +			.bw = bandwidth,
> +		},
> +	};
> +	struct tegra_bpmp_message msg = {
> +		.mrq = MRQ_SOCHUB_MBWT,
> +		.tx = {
> +			.data = &request,
> +			.size = sizeof(request),
> +		},
> +	};
> +	int err;
> +
> +	err = tegra_bpmp_transfer(bpmp, &msg);
> +	if (err) {
> +		dev_err(bpmp->dev, "MBWT set bandwidth transfer failed: %d\n",
> +			err);
> +		return err;
> +	}
> +
> +	if (msg.rx.ret)
> +		return msg.rx.ret;
> +
> +	return 0;
> +}
> +
>  static void tegra_bpmp_mrq_handle_ping(unsigned int mrq,
>  				       struct tegra_bpmp_channel *channel,
>  				       void *data)
> -- 
> 2.43.0
> 

Since these are only used by the sysfs code, I would squash this patch 
into the sysfs patch and move these functions into the sysfs file.