linux-kernel - Re: [PATCH RFC RFT] interconnect: qcom: implement get_bw with rpmh

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Message-ID: <8eb528dd-71fc-408e-a97c-d484198e4f81@kernel.org>
Date: Tue, 13 Jan 2026 19:53:33 +0200
From: Georgi Djakov <djakov@...nel.org>
To: Neil Armstrong <neil.armstrong@...aro.org>
Cc: linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC RFT] interconnect: qcom: implement get_bw with
 rpmh_read

On 11/6/25 6:46 PM, Neil Armstrong wrote:
> Since we can actually read back the APPS rpmh interconnect
> BCM votes we can actually implement the get_bw() callback
> and provide a coherent average and peak bandwidth at probe time.
> 
> The benefits of that are:
> - keep disabled BCMs disabled
> - avoid voting unused BCMs to INT_MAX
> 
> If the interconnects are correctly described for a platform,
> all the required BCMs would be voted to the maximum bandwidth
> until sync_state is reached.
> 
> Since we only get the BCM vote, we need to redistribute
> the vote values to the associated nodes. The initial BCM
> votes are read back at probe time in order to be ready when
> the get_bw() is called when a node is added.
> 

FWIW, I was able to finally test this on sdm845. Some nodes are indeed
showing reasonable bandwidth values instead of the default INT_MAX.

Tested-by: Georgi Djakov <djakov@...nel.org> #db845c

> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---
> Depends on:
> https://lore.kernel.org/all/20251022-add-rpmh-read-support-v2-2-5c7a8e4df601@oss.qualcomm.com/
> ---
>   drivers/interconnect/qcom/bcm-voter.c | 36 +++++++++++++++++++++
>   drivers/interconnect/qcom/bcm-voter.h |  2 ++
>   drivers/interconnect/qcom/icc-rpmh.c  | 60 ++++++++++++++++++++++++++++++++++-
>   3 files changed, 97 insertions(+), 1 deletion(-)
>