linux-kernel - Re: [PATCH v2 4/5] ARM: dts: imx7: add GPMI NAND

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Date:   Thu, 4 May 2017 22:59:52 +0000
From:   Han Xu <han.xu@....com>
To:     Stefan Agner <stefan@...er.ch>
CC:     "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "boris.brezillon@...e-electrons.com" 
        <boris.brezillon@...e-electrons.com>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>,
        "richard@....at" <richard@....at>,
        "cyrille.pitchen@...el.com" <cyrille.pitchen@...el.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "fabio.estevam@...escale.com" <fabio.estevam@...escale.com>,
        "LW@...O-electronics.de" <LW@...o-electronics.de>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/5] ARM: dts: imx7: add GPMI NAND



On 05/04/2017 04:50 PM, Stefan Agner wrote:
> On 2017-05-04 12:13, Han Xu wrote:
>> On 04/21/2017 08:23 PM, Stefan Agner wrote:
>>> Add i.MX 7 GPMI NAND module.
>>>
>>> Signed-off-by: Stefan Agner <stefan@...er.ch>
>>> ---
>>>    arch/arm/boot/dts/imx7s.dtsi | 31 +++++++++++++++++++++++++++++++
>>>    1 file changed, 31 insertions(+)
>>>
>>> diff --git a/arch/arm/boot/dts/imx7s.dtsi b/arch/arm/boot/dts/imx7s.dtsi
>>> index 843eb379e1ea..9645257638d4 100644
>>> --- a/arch/arm/boot/dts/imx7s.dtsi
>>> +++ b/arch/arm/boot/dts/imx7s.dtsi
>>> @@ -995,5 +995,36 @@
>>>    				status = "disabled";
>>>    			};
>>>    		};
>>> +
>>> +		dma_apbh: dma-apbh@...00000 {
>>> +			compatible = "fsl,imx7d-dma-apbh", "fsl,imx28-dma-apbh";
>>> +			reg = <0x33000000 0x2000>;
>>> +			interrupts = <GIC_SPI 12 IRQ_TYPE_LEVEL_HIGH>,
>>> +				     <GIC_SPI 12 IRQ_TYPE_LEVEL_HIGH>,
>>> +				     <GIC_SPI 12 IRQ_TYPE_LEVEL_HIGH>,
>>> +				     <GIC_SPI 12 IRQ_TYPE_LEVEL_HIGH>;
>>> +			interrupt-names = "gpmi0", "gpmi1", "gpmi2", "gpmi3";
>>> +			#dma-cells = <1>;
>>> +			dma-channels = <4>;
>>> +			clocks = <&clks IMX7D_NAND_USDHC_BUS_ROOT_CLK>,
>>> +				<&clks IMX7D_NAND_ROOT_CLK>;
>>> +			clock-names = "dma_apbh_bch", "dma_apbh_io";
>>> +		};
>> Do you need some patches to enable all clks for APBH DMA? Refer to
>> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.ozlabs.org%2Fpatch%2F551967%2F&data=01%7C01%7Chan.xu%40nxp.com%7C98493f7e475341dbf67008d49337b441%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0&sdata=FH9k%2FC4VcVCeyidkRgUJ5Ahu4%2B%2FlDAjXVwO0DY7XMhA%3D&reserved=0
>>
> Oh I see, with the current code and this device tree we actually only
> enable the first clock... But it seems to work in practice...
>
> What is interesting, the chapter 5.2.5 System Clocks only describes
> APBHDMA, and no GPMI module.
>
> Chapter 9.4 about APBH-Bridge-DMA bridge only specifies "hclk" as clock
> sources.
>
> When looking at the table in chapter 5.2.5, hclk is
> NAND_USDHC_BUS_CLK_ROOT
>
> Module    Syste Module Clock   Clock Root
> APBHDMA   apbhdma.hclk         NAND_USDHC_BUS_CLK_ROOT
>   
> So my guess is that the actual DMA controller should work fine with
> IMX7D_NAND_USDHC_BUS_ROOT_CLK only. It is only the GPMI module which
> needs the NAND_ROOT_CLK. My guess is since the APBHDMA controller is
> only used for GPMI these days, it has been combined in one module in the
> table in chapter 5.2.5.
>
> So we could actually only specify:
>
> clocks = <&clks IMX7D_NAND_USDHC_BUS_ROOT_CLK>;
>
> Tested with this and NAND seems to work fine.
>
> Also tested accessing APBHDMA register in U-Boot with
> IMX7D_NAND_ROOT_CLK disabled, it worked fine.
>
> What do you think? Should we go with this?
>
> This probably even saves power since GPMI's runtime clock management
> disables IMX7D_NAND_ROOT_CLK when NAND is idle (according to the
> nand_root_clk counter in clk_summary and the root clock register at
> 0x3038AA00).

It also surprised me how it can work on your side, I remember we made 
the code change for some purpose, please give me some time I can check 
if the doc is wrong.

> --
> Stefan
>
>>> +
>>> +		gpmi: gpmi-nand@...02000{
>>> +			compatible = "fsl,imx7d-gpmi-nand";
>>> +			#address-cells = <1>;
>>> +			#size-cells = <1>;
>>> +			reg = <0x33002000 0x2000>, <0x33004000 0x4000>;
>>> +			reg-names = "gpmi-nand", "bch";
>>> +			interrupts = <GIC_SPI 14 IRQ_TYPE_LEVEL_HIGH>;
>>> +			interrupt-names = "bch";
>>> +			clocks = <&clks IMX7D_NAND_ROOT_CLK>,
>>> +				<&clks IMX7D_NAND_USDHC_BUS_ROOT_CLK>;
>>> +			clock-names = "gpmi_io", "gpmi_bch_apb";
>>> +			dmas = <&dma_apbh 0>;
>>> +			dma-names = "rx-tx";
>>> +			status = "disabled";
>>> +		};
>>>    	};
>>>    };