Message-ID: <efbc7027-5717-ba29-2b6c-e9b780558315@quicinc.com>
Date:   Wed, 8 Mar 2023 11:22:27 +0530
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Subject: Re: [PATCH 7/8] arm64: dts: qcom: ipq9574: Add USB related nodes
To:     Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
CC:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        <linux-arm-msm@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, Georgi Djakov <djakov@kernel.org>
References: <cover.1677749625.git.quic_varada@quicinc.com>
 <6b8d17006d8ee9a1b0c4df803c1cc7caf53ea3ef.1677749625.git.quic_varada@quicinc.com>
 <CAA8EJprbMybV0o1-436yLhVnnEX6qywrj=JmWDCL5usaH0DXiQ@mail.gmail.com>
 <61e8c730-e46d-728d-d770-f1ead4405d12@quicinc.com>
 <83184da4-b183-3271-983f-3a1a62fb9f1a@linaro.org>
 <365f2609-d3b4-df23-5b6e-7a190815a640@quicinc.com>
 <47b591c0-2f68-429d-6d1b-fa8b701785ac@linaro.org>
Content-Language: en-US
From:   Varadarajan Narayanan <quic_varada@quicinc.com>
In-Reply-To: <47b591c0-2f68-429d-6d1b-fa8b701785ac@linaro.org>
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On 3/7/2023 5:19 PM, Dmitry Baryshkov wrote:
> On 07/03/2023 08:36, Varadarajan Narayanan wrote:
>>
>> On 3/6/2023 5:21 PM, Dmitry Baryshkov wrote:
>>> On 06/03/2023 13:26, Varadarajan Narayanan wrote:
>>>> Dmitry,
>>>>
>>>> On 3/2/2023 9:52 PM, Dmitry Baryshkov wrote:
>>>>> On Thu, 2 Mar 2023 at 11:57, Varadarajan Narayanan
>>>>> <quic_varada@quicinc.com> wrote:
>>>>>> Add USB phy and controller related nodes
>>>>>>
>>>>>> Signed-off-by: Varadarajan Narayanan <quic_varada@quicinc.com>
>>>>>> ---
>>>>>>   arch/arm64/boot/dts/qcom/ipq9574.dtsi | 92 
>>>>>> +++++++++++++++++++++++++++++++++++
>>>>>>   1 file changed, 92 insertions(+)
>>>>>>
>>>>>> diff --git a/arch/arm64/boot/dts/qcom/ipq9574.dtsi 
>>>>>> b/arch/arm64/boot/dts/qcom/ipq9574.dtsi
>>>>>> index 2bb4053..319b5bd 100644
>>>>>> --- a/arch/arm64/boot/dts/qcom/ipq9574.dtsi
>>>>>> +++ b/arch/arm64/boot/dts/qcom/ipq9574.dtsi
>>>
>>> [skipped]
>>>
>>>
>>>>>> +               usb3: usb3@8A00000 {
>>>>> You know the drill. This node is in the wrong place.
>>>>>
>>>>>> +                       compatible = "qcom,dwc3";
>>>>>> +                       reg = <0x8AF8800 0x400>;
>>>>>> +                       #address-cells = <1>;
>>>>>> +                       #size-cells = <1>;
>>>>>> +                       ranges;
>>>>>> +
>>>>>> +                       clocks = <&gcc GCC_SNOC_USB_CLK>,
>>>>>> +                               <&gcc GCC_ANOC_USB_AXI_CLK>,
>>>>>> +                               <&gcc GCC_USB0_MASTER_CLK>,
>>>>>> +                               <&gcc GCC_USB0_SLEEP_CLK>,
>>>>>> +                               <&gcc GCC_USB0_MOCK_UTMI_CLK>;
>>>>>> +
>>>>>> +                       clock-names = "sys_noc_axi",
>>>>>> +                               "anoc_axi",
>>>>>> +                               "master",
>>>>>> +                               "sleep",
>>>>>> +                               "mock_utmi";
>>>>> Please fix the indentation of the lists.
>>>>>
>>>>>> +
>>>>>> +                       assigned-clocks = <&gcc GCC_SNOC_USB_CLK>,
>>>>>> +                                         <&gcc 
>>>>>> GCC_ANOC_USB_AXI_CLK>,
>>>>> Why do you assign clock rates to the NOC clocks? Should they be set
>>>>> using the interconnect instead?
>>>>
>>>> The SNOC and ANOC run at a fixed speed of 350MHz and 342MHz 
>>>> respectively and are not scaled. These clocks are for the interface 
>>>> between the USB block and the SNOC/ANOC. Do we still need to use 
>>>> interconnect?
>>>
>>> Maybe I misunderstand something here. If the snoc and anoc speeds 
>>> are at 350 MHz and 342 MHz, why do you assign clock-rates of 200 MHz?
>>>
>>> Is it enough to call clk_prepare_enable() for these clocks or the 
>>> rate really needs to be set?
>>
>> The rate of 200MHz is not being set for the SNOC/ANOC. It is for the
>> NIU that connects the USB and SNOC/ANOC. The reason for setting the
>> rate to 200MHz is to configure the RCG parent for these interface
>> clocks. That said can we configure this RCG standalone in the driver
>> and enable these clocks?
>
> We discussed this separately with Georgi Djakov. Let me quote his IRC 
> message: "it sounds like this is for USB port that connects to the 
> NOC. if bandwidth scaling is not needed (or other interconnect 
> configuration), then maybe this can go without interconnect provider 
> driver."
>
> However as we discover more and more about this platform (e.g. PCIe 
> using the aggre_noc region to setup some magic registers, see [1]), 
> I'm more and more biased towards suggesting implementing the 
> interconnect driver to setup all these tiny little things. With the DT 
> tree being an ABI, it is much preferable to overestimate the needs 
> rather than underestimating them (and having to cope with the 
> backwards compatibility issues).
>
> Generally I think that PCIe/USB/whatever should not poke into NoC 
> registers or NoC/NIU clocks directly (because this is a very 
> platform-specific item). Rather than that it should tell the 
> icc/opp/whatever subsystem, "please configure the SoC for me to work".
>
> [1] 
> https://lore.kernel.org/linux-arm-msm/30cf9717-dcca-e984-c506-c71b7f8e32cd@quicinc.com/


Sure, will post a new revision that uses interconnect subsystem.

Thanks
Varada

>>>>>> + <&gcc GCC_USB0_MASTER_CLK>,
>>>>>> +                                         <&gcc 
>>>>>> GCC_USB0_MOCK_UTMI_CLK>;
>>>>>> +                       assigned-clock-rates = <200000000>,
>>>>>> + <200000000>,
>>>>>> + <200000000>,
>>>>>> + <24000000>;
>>>>>> +
>>>>>> +                       resets = <&gcc GCC_USB_BCR>;
>>>>>> +                       status = "disabled";
>>>>>> +
>>>>>> +                       dwc_0: dwc3@8A00000 {
>>>>>> +                               compatible = "snps,dwc3";
>>>>>> +                               reg = <0x8A00000 0xcd00>;
>>>>>> +                               clock-names = "ref";
>>>>>> +                               clocks = <&gcc 
>>>>>> GCC_USB0_MOCK_UTMI_CLK>;
>>>>> clocks before clock-names
>>>>>
>>>>>> + interrupts = <GIC_SPI 140 IRQ_TYPE_LEVEL_HIGH>;
>>>>>> +                               phys = <&qusb_phy_0>, <&usb0_ssphy>;
>>>>>> +                               phy-names = "usb2-phy", "usb3-phy";
>>>>>> +                               tx-fifo-resize;
>>>>>> + snps,dis_ep_cache_eviction;
>>>>>> +                               snps,is-utmi-l1-suspend;
>>>>>> +                               snps,hird-threshold = /bits/ 8 
>>>>>> <0x0>;
>>>>>> + snps,dis_u2_susphy_quirk;
>>>>>> + snps,dis_u3_susphy_quirk;
>>>>>> + snps,quirk-frame-length-adjustment = <0x0A87F0A0>;
>>>>>> +                               dr_mode = "host";
>>>>>> +                       };
>>>>>> +               };
>>>>>> +
>>>>>>                  pcie0_phy: phy@84000 {
>>>>>>                          compatible = 
>>>>>> "qcom,ipq9574-qmp-gen3x1-pcie-phy";
>>>>>>                          reg = <0x00084000 0x1bc>; /* Serdes PLL */
>>>>>> -- 
>>>>>> 2.7.4
>>>>
>>>> Will address these and post a new revision.
>>>>
>>>> Thanks
>>>>
>>>> Varada
>>>>
>>>
>