linux-kernel - Re: [PATCH 2/5] arm64: dts: qcom: lemans: Add SDHC controller and SDC pin configuration

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Message-ID: <aLwOZMgfRrvQJzPu@hu-mchunara-hyd.qualcomm.com>
Date: Sat, 6 Sep 2025 16:05:16 +0530
From: Monish Chunara <quic_mchunara@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
CC: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Wasim Nazir
	<wasim.nazir@....qualcomm.com>,
        Ulf Hansson <ulf.hansson@...aro.org>, "Rob
 Herring" <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        "Conor
 Dooley" <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        "Konrad Dybcio" <konradybcio@...nel.org>,
        Richard Cochran
	<richardcochran@...il.com>, <kernel@....qualcomm.com>,
        <linux-mmc@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH 2/5] arm64: dts: qcom: lemans: Add SDHC controller and
 SDC pin configuration

On Sat, Sep 06, 2025 at 10:28:47AM +0200, Konrad Dybcio wrote:
> On 9/5/25 3:44 PM, Dmitry Baryshkov wrote:
> > On Fri, Sep 05, 2025 at 02:04:47PM +0200, Konrad Dybcio wrote:
> >> On 9/5/25 1:45 PM, Dmitry Baryshkov wrote:
> >>> On Fri, Sep 05, 2025 at 01:14:29PM +0200, Konrad Dybcio wrote:
> >>>> On 9/4/25 7:32 PM, Dmitry Baryshkov wrote:
> >>>>> On Thu, Sep 04, 2025 at 04:34:05PM +0200, Konrad Dybcio wrote:
> >>>>>> On 9/4/25 3:35 PM, Dmitry Baryshkov wrote:
> >>>>>>> On Wed, Sep 03, 2025 at 09:58:33PM +0530, Wasim Nazir wrote:
> >>>>>>>> On Wed, Sep 03, 2025 at 06:12:59PM +0200, Konrad Dybcio wrote:
> >>>>>>>>> On 8/27/25 3:20 AM, Dmitry Baryshkov wrote:
> >>>>>>>>>> On Tue, Aug 26, 2025 at 11:51:01PM +0530, Wasim Nazir wrote:
> >>>>>>>>>>> From: Monish Chunara <quic_mchunara@...cinc.com>
> >>>>>>>>>>>
> >>>>>>>>>>> Introduce the SDHC v5 controller node for the Lemans platform.
> >>>>>>>>>>> This controller supports either eMMC or SD-card, but only one
> >>>>>>>>>>> can be active at a time. SD-card is the preferred configuration
> >>>>>>>>>>> on Lemans targets, so describe this controller.
> >>>>>>>>>>>
> >>>>>>>>>>> Define the SDC interface pins including clk, cmd, and data lines
> >>>>>>>>>>> to enable proper communication with the SDHC controller.
> >>>>>>>>>>>
> >>>>>>>>>>> Signed-off-by: Monish Chunara <quic_mchunara@...cinc.com>
> >>>>>>>>>>> Co-developed-by: Wasim Nazir <wasim.nazir@....qualcomm.com>
> >>>>>>>>>>> Signed-off-by: Wasim Nazir <wasim.nazir@....qualcomm.com>
> >>>>>>>>>>> ---
> >>>>>>>>>>>  arch/arm64/boot/dts/qcom/lemans.dtsi | 70 ++++++++++++++++++++++++++++++++++++
> >>>>>>>>>>>  1 file changed, 70 insertions(+)
> >>>>>>>>>>>
> >>>>>>>>>>> diff --git a/arch/arm64/boot/dts/qcom/lemans.dtsi b/arch/arm64/boot/dts/qcom/lemans.dtsi
> >>>>>>>>>>> index 99a566b42ef2..a5a3cdba47f3 100644
> >>>>>>>>>>> --- a/arch/arm64/boot/dts/qcom/lemans.dtsi
> >>>>>>>>>>> +++ b/arch/arm64/boot/dts/qcom/lemans.dtsi
> >>>>>>>>>>> @@ -3834,6 +3834,36 @@ apss_tpdm2_out: endpoint {
> >>>>>>>>>>>  			};
> >>>>>>>>>>>  		};
> >>>>>>>>>>>  
> >>>>>>>>>>> +		sdhc: mmc@...4000 {
> >>>>>>>>>>> +			compatible = "qcom,sa8775p-sdhci", "qcom,sdhci-msm-v5";
> >>>>>>>>>>> +			reg = <0x0 0x087c4000 0x0 0x1000>;
> >>>>>>>>>>> +
> >>>>>>>>>>> +			interrupts = <GIC_SPI 383 IRQ_TYPE_LEVEL_HIGH>,
> >>>>>>>>>>> +				     <GIC_SPI 521 IRQ_TYPE_LEVEL_HIGH>;
> >>>>>>>>>>> +			interrupt-names = "hc_irq", "pwr_irq";
> >>>>>>>>>>> +
> >>>>>>>>>>> +			clocks = <&gcc GCC_SDCC1_AHB_CLK>,
> >>>>>>>>>>> +				 <&gcc GCC_SDCC1_APPS_CLK>;
> >>>>>>>>>>> +			clock-names = "iface", "core";
> >>>>>>>>>>> +
> >>>>>>>>>>> +			interconnects = <&aggre1_noc MASTER_SDC 0 &mc_virt SLAVE_EBI1 0>,
> >>>>>>>>>>> +					<&gem_noc MASTER_APPSS_PROC 0 &config_noc SLAVE_SDC1 0>;
> >>>>>>>>>>> +			interconnect-names = "sdhc-ddr", "cpu-sdhc";
> >>>>>>>>>>> +
> >>>>>>>>>>> +			iommus = <&apps_smmu 0x0 0x0>;
> >>>>>>>>>>> +			dma-coherent;
> >>>>>>>>>>> +
> >>>>>>>>>>> +			resets = <&gcc GCC_SDCC1_BCR>;
> >>>>>>>>>>> +
> >>>>>>>>>>> +			no-sdio;
> >>>>>>>>>>> +			no-mmc;
> >>>>>>>>>>> +			bus-width = <4>;
> >>>>>>>>>>
> >>>>>>>>>> This is the board configuration, it should be defined in the EVK DTS.
> >>>>>>>>>
> >>>>>>>>> Unless the controller is actually incapable of doing non-SDCards
> >>>>>>>>>
> >>>>>>>>> But from the limited information I can find, this one should be able
> >>>>>>>>> to do both
> >>>>>>>>>
> >>>>>>>>
> >>>>>>>> It’s doable, but the bus width differs when this controller is used for
> >>>>>>>> eMMC, which is supported on the Mezz board. So, it’s cleaner to define
> >>>>>>>> only what’s needed for each specific usecase on the board.
> >>>>>>>
> >>>>>>> `git grep no-sdio arch/arm64/boot/dts/qcom/` shows that we have those
> >>>>>>> properties inside the board DT. I don't see a reason to deviate.
> >>>>>>
> >>>>>> Just to make sure we're clear
> >>>>>>
> >>>>>> I want the author to keep bus-width in SoC dt and move the other
> >>>>>> properties to the board dt
> >>>>>
> >>>>> I think bus-width is also a property of the board. In the end, it's a
> >>>>> question of schematics whether we route 1 wire or all 4 wires. git-log
> >>>>> shows that bus-width is being sent in both files (and probalby we should
> >>>>> sort that out).
> >>>>
> >>>> Actually this is the controller capability, so if it can do 8, it should
> >>>> be 8 and the MMC core will do whatever it pleases (the not-super-sure
> >>>> docs that I have say 8 for this platform)
> >>>
> >>> Isn't it a physical width of the bus between the controller and the slot
> >>> or eMMC chip?
> >>
> >> No, that's matched against reported (sd/mmc) card capabilities IIUC
> > 
> > What if both host and the card support 4 bits bus (normal SD card), but
> > board has only one data wire?
> 
> Ohhh, touche.. I assumed it's "smart" like PCIe, but it's (probably)
> not.
> 
> Sorry for the trouble, Wasim. Let's keep 4 for now and get this patch
> merged.
> 
> Konrad>

Thanks for the discussion Dmitry and Konrad. This has been confirmed with
hardware team as well that only 4 lines have been routed from the controller to
the SD card slot on the board, as per the card specifications.

We'll keep the value 4 in the board DTS as per the discussion.

Best Regards,
Monish