linux-kernel - Re: [PATCH v5 4/5] dt-bindings: mtd: Add bindings for TI's AM654 HyperBus memory controller

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Message-ID: <7c7828b9-bcfd-6156-3ddb-cbdde5956675@ti.com>
Date:   Mon, 17 Jun 2019 10:00:45 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Rob Herring <robh+dt@...nel.org>
CC:     <linux-mtd@...ts.infradead.org>,
        Tudor Ambarus <Tudor.Ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Joakim Tjernlund <Joakim.Tjernlund@...inera.com>,
        <devicetree@...r.kernel.org>, Mason Yang <masonccyang@...c.com.tw>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 4/5] dt-bindings: mtd: Add bindings for TI's AM654
 HyperBus memory controller

Hi,

On 10/06/19 9:55 PM, Sergei Shtylyov wrote:
> Hello!
> 
> On 06/09/2019 01:32 PM, Vignesh Raghavendra wrote:
> 
>> Add binding documentation for TI's HyperBus memory controller present on
>> AM654 SoC.
>>
>> Signed-off-by: Vignesh Raghavendra <vigneshr@...com>
>> ---
>> v5:
>> Update binding example to show MMIO mux
>> Fix reg property for flash slave.
>>
>>  .../devicetree/bindings/mtd/ti,am654-hbmc.txt | 51 +++++++++++++++++++
>>  MAINTAINERS                                   |  1 +
>>  2 files changed, 52 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/mtd/ti,am654-hbmc.txt
>>
>> diff --git a/Documentation/devicetree/bindings/mtd/ti,am654-hbmc.txt b/Documentation/devicetree/bindings/mtd/ti,am654-hbmc.txt
>> new file mode 100644
>> index 000000000000..c2a2c2b42a92
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/mtd/ti,am654-hbmc.txt
>> @@ -0,0 +1,51 @@
>> +Bindings for HyperBus Memory Controller (HBMC) on TI's K3 family of SoCs
>> +
>> +Required properties:
>> +- compatible : "ti,am654-hbmc" for AM654 SoC
>> +- reg : Two entries:
>> +	First entry pointed to the register space of HBMC controller
>> +	Second entry pointing to the memory map region dedicated for
>> +	MMIO access to attached flash devices
>> +- ranges : Address translation from offset within CS to allocated MMIO
>> +	   space in SoC
>> +
>> +Optional properties:
>> +- mux-controls : phandle to the multiplexer that controls selection of
>> +		 HBMC vs OSPI inside Flash SubSystem. Default is OSPI,
>> +		 if property is absent.
>> +		 See Documentation/devicetree/bindings/mux/reg-mux.txt
>> +		 for mmio-mux binding details
>> +
>> +Example:
>> +
>> +	fss: fss@...00000 {
> 
>    What's FSS?

Flash SubSystem (FSS). Will highlight that in mux control definition above

>    Regardless of the answer, the node names should be generic, like "memory-controller@".
> 
>> +		compatible = "syscon", "simple-mfd";
> 
>    If it's "sycon", the nme should probably be "system-controller".

FSS is like a subchip that has all Flash controllers like Octal SPI
controllers and HyperBus controller within it. Some of their controls
are in the below address range. So I think its more closer to
"system-controller"

> 
>> +		reg = <0x0 0x47000000 0x0 0x100>;
>> +		#address-cells = <2>;
>> +		#size-cells = <2>;
>> +		ranges;
>> +
>> +		hbmc_mux: hbmc-mux {
> 
>    So, just "multiplexor"?

Ok

> 
>> +			compatible = "mmio-mux";
>> +			#mux-control-cells = <1>;
>> +			mux-reg-masks = <0x4 0x2>; /* 0: reg 0x4, bit 1 */
>> +		};
>> +
>> +		hbmc: hbmc@...34000 {
> 
>    Should be named "memory-controller@...34000", according to the DT spec.

IMO, since HyperBus is a bus protocol and has a specification, I think
its should have a separate generic name like SPI etc.

I will change this to "hyperbus@...34000" to common name of spec.

> 
>> +			compatible = "ti,am654-hbmc";
>> +			reg = <0x0 0x47034000 0x0 0x100>,
>> +				<0x5 0x00000000 0x1 0x0000000>;
>> +			power-domains = <&k3_pds 55>;
>> +			#address-cells = <2>;
>> +			#size-cells = <1>;
>> +			ranges = <0x0 0x0 0x5 0x00000000 0x4000000>, /* CS0 - 64MB */
>> +				 <0x1 0x0 0x5 0x04000000 0x4000000>; /* CS1 - 64MB */
>> +			mux-controls = <&hbmc_mux 0>;
>> +
>> +			/* Slave flash node */
>> +			flash@0,0 {
>> +				compatible = "cypress,hyperflash", "cfi-flash";
>> +				reg = <0x0 0x0 0x4000000>;
>> +			};
>> +		};
>> +	};
> [...]
> 
> MBR, Sergei
> 

-- 
Regards
Vignesh