linux-kernel - Re: [PATCH 2/4] clk: qcom: gcc: Add support for Global Clock controller found on MSM8940

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Message-ID: <13b44a8c-357d-4f98-8762-640179fe3ff3@oss.qualcomm.com>
Date: Mon, 1 Dec 2025 13:26:59 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: barnabas.czeman@...nlining.org
Cc: Taniya Das <taniya.das@....qualcomm.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd
 <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Adam Skladowski <a_skl39@...tonmail.com>,
        Sireesh Kodali <sireeshkodali@...tonmail.com>,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lanik <daniilt971@...il.com>
Subject: Re: [PATCH 2/4] clk: qcom: gcc: Add support for Global Clock
 controller found on MSM8940

On 11/30/25 3:50 PM, barnabas.czeman@...nlining.org wrote:
> On 2025-11-17 15:17, Konrad Dybcio wrote:
>> On 11/17/25 3:02 PM, barnabas.czeman@...nlining.org wrote:
>>> On 2025-11-17 13:17, Konrad Dybcio wrote:
>>>> On 11/17/25 9:51 AM, Barnabás Czémán wrote:
>>>>>
>>>>>
>>>>> On 17 November 2025 09:03:53 CET, Taniya Das <taniya.das@....qualcomm.com> wrote:
>>>>>>
>>>>>>
>>>>>> On 11/17/2025 3:05 AM, Barnabás Czémán wrote:
>>>>>>>
>>>>>>> +static struct clk_branch gcc_ipa_tbu_clk = {
>>>>>>> +    .halt_reg = 0x120a0,
>>>>>>> +    .halt_check = BRANCH_VOTED,
>>>>>>> +    .clkr = {
>>>>>>> +        .enable_reg = 0x4500c,
>>>>>>> +        .enable_mask = BIT(16),
>>>>>>> +        .hw.init = &(struct clk_init_data){
>>>>>>> +            .name = "gcc_ipa_tbu_clk",
>>>>>>> +            .ops = &clk_branch2_ops,
>>>>>>> +        },
>>>>>>> +    },
>>>>>>> +};
>>>>>>> +
>>>>>>
>>>>>> Is the TBU clock used on 8940 by a SMMU driver?
>>>>> As far as I know no MSM8940 is using same smmu driver and bindings like MSM8937.
>>>>
>>>> On msm8939, the clock needed to be turned on for the GPU SMMU
>>> I have not got any qcom-iommu issues on 8940 but i think it could come when i try to add ipa2 driver
>>> for the SoC until i do not know where to check it.
>>
>> I can't find a definitive answer, but it's most certainly going to be
>> necessary to turn it on
>>
>> Konrad
> 
> I have enabled ipa2-lite for 8940 at downstream and it can cause gpu to crash.

Really!?

FWIW the clock on 8939 is called GCC_*GFX*_TBU_CLK so it being related
made more sense. Here, I see no connection :/

Konrad

> I have tried to add TBU clock for apps_iommu but it not fixing the issue.
> 
> Here are the iommu changes based on 8937 apps_iommu node:
> +&apps_iommu {
> +       clocks = <&gcc GCC_SMMU_CFG_CLK>,
> +                <&gcc GCC_APSS_TCU_CLK>,
> +                <&gcc MSM8940_GCC_IPA_TBU_CLK>;
> +       clock-names = "iface",
> +                     "bus",
> +                     "tbu";
> +
> +       /* IPA */
> +       iommu-ctx@...00 {
> +               compatible = "qcom,msm-iommu-v1-ns";
> +               reg = <0x18000 0x1000>;
> +               interrupts = <GIC_SPI 115 IRQ_TYPE_LEVEL_HIGH>;
> +       };
> +};
> +
>