linux-kernel - Re: [PATCH v3 3/7] soc: qcom: icc-bwmon: Handle global registers correctly

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Date:   Thu, 16 Mar 2023 07:38:39 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Georgi Djakov <djakov@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Thara Gopinath <thara.gopinath@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Marijn Suijten <marijn.suijten@...ainline.org>
Subject: Re: [PATCH v3 3/7] soc: qcom: icc-bwmon: Handle global registers
 correctly

On 15/03/2023 15:11, Konrad Dybcio wrote:
> The BWMON hardware has two sets of registers: one for the monitor itself
> and one called "global". It has what seems to be some kind of a head
> switch and an interrupt control register. It's usually 0x200 in size.
> 
> On fairly recent SoCs (with the starting point seemingly being moving
> the OSM programming to the firmware) these two register sets are
> contiguous and overlapping, like this (on sm8450):
> 
> /* notice how base.start == global_base.start+0x100 */
> reg = <0x90b6400 0x300>, <0x90b6300 0x200>;
> reg-names = "base", "global_base";
> 
> Which led to some confusion and the assumption that since the
> "interesting" global registers begin right after global_base+0x100,
> there's no need to map two separate regions and one can simply subtract
> 0x100 from the offsets.
> 
> This is however not the case for anything older than SDM845, as the
> global region can appear in seemingly random spots on the register map.
> 
> Handle the case where the global registers are mapped separately to allow
> proper functioning of BWMONv4 on MSM8998 and older. Add specific
> compatibles for 845, 8280xp, 7280 and 8550 (all of which use the single
> reg space scheme) to keep backwards compatibility with old DTs.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
>  drivers/soc/qcom/icc-bwmon.c | 230 +++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 209 insertions(+), 21 deletions(-)
> 

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Best regards,
Krzysztof