linux-kernel - Re: [PATCH v4 03/10] dt-bindings: spi: Adjust the bindings for the FSL QSPI driver

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Date:   Thu, 8 Nov 2018 08:48:37 +0000
From:   Schrempf Frieder <frieder.schrempf@...tron.De>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
CC:     "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>,
        "richard@....at" <richard@....at>,
        "miquel.raynal@...tlin.com" <miquel.raynal@...tlin.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "david.wolfe@....com" <david.wolfe@....com>,
        "fabio.estevam@....com" <fabio.estevam@....com>,
        "prabhakar.kushwaha@....com" <prabhakar.kushwaha@....com>,
        "yogeshnarayan.gaur@....com" <yogeshnarayan.gaur@....com>,
        "han.xu@....com" <han.xu@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Frieder Schrempf <frieder.schrempf@...eet.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 03/10] dt-bindings: spi: Adjust the bindings for the
 FSL QSPI driver

On 08.11.18 09:41, Boris Brezillon wrote:
> On Wed,  7 Nov 2018 15:43:20 +0100
> Frieder Schrempf <frieder.schrempf@...tron.de> wrote:
> 
>> From: Frieder Schrempf <frieder.schrempf@...eet.de>
>>
>> Adjust the documentation of the new SPI memory interface based
>> driver to reflect the new drivers settings.
>>
>> The "old" driver was using the "fsl,qspi-has-second-chip" property to
>> select one of two dual chip setups (two chips on one bus or two chips
>> on separate buses). And it used the order in which the subnodes are
>> defined in the dt to select the CS, the chip is connected to.
>>
>> Both methods are wrong and in fact the "reg" property should be used to
>> determine which bus and CS a chip is connected to. This also enables us
>> to use different setups than just single chip, or symmetric dual chip.
>>
>> So the porting of the driver from the MTD to the SPI framework actually
>> enforces the use of the "reg" properties and makes
>> "fsl,qspi-has-second-chip" superfluous.
>>
>> As all boards that have "fsl,qspi-has-second-chip" set, also have
>> correct "reg" properties, the removal of this property shouldn't lead to
>> any incompatibilities.
>>
>> The only compatibility issues I can see are with imx6sx-sdb.dts and
>> imx6sx-sdb-reva.dts, which have their reg properties set incorrectly
>> (see explanation here: [2]), all other boards should stay compatible.
>>
>> Also the "big-endian" flag was removed, as this setting is now selected
>> by the driver, depending on which SoC is in use.
>>
>> Signed-off-by: Frieder Schrempf <frieder.schrempf@...eet.de>
>> ---
>>   .../devicetree/bindings/spi/spi-fsl-qspi.txt    | 21 +++++++++-----------
>>   1 file changed, 9 insertions(+), 12 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/spi/spi-fsl-qspi.txt b/Documentation/devicetree/bindings/spi/spi-fsl-qspi.txt
>> index 483e9cf..6d7c9ec 100644
>> --- a/Documentation/devicetree/bindings/spi/spi-fsl-qspi.txt
>> +++ b/Documentation/devicetree/bindings/spi/spi-fsl-qspi.txt
>> @@ -3,9 +3,8 @@
>>   Required properties:
>>     - compatible : Should be "fsl,vf610-qspi", "fsl,imx6sx-qspi",
>>   		 "fsl,imx7d-qspi", "fsl,imx6ul-qspi",
>> -		 "fsl,ls1021a-qspi"
>> +		 "fsl,ls1021a-qspi", "fsl,ls2080a-qspi"
>>   		 or
>> -		 "fsl,ls2080a-qspi" followed by "fsl,ls1021a-qspi",
> 
> Looks like this change is not related to this commit, and I'm not sure
> it's even needed. Plus, the order differs from the previous
> description, so, if the doc was right before this change it should be:
> 
> 		"fsl,ls2080a-qspi", "fsl,ls1021a-qspi"

Right, there already was a discussion with Rob about that on v2 [1].
I forgot to drop this change.

[1] https://patchwork.ozlabs.org/patch/939868/

>>   		 "fsl,ls1043a-qspi" followed by "fsl,ls1021a-qspi"
>>     - reg : the first contains the register location and length,
>>             the second contains the memory mapping address and length
>> @@ -14,15 +13,13 @@ Required properties:
>>     - clocks : The clocks needed by the QuadSPI controller
>>     - clock-names : Should contain the name of the clocks: "qspi_en" and "qspi".
>>   
>> -Optional properties:
>> -  - fsl,qspi-has-second-chip: The controller has two buses, bus A and bus B.
>> -                              Each bus can be connected with two NOR flashes.
>> -			      Most of the time, each bus only has one NOR flash
>> -			      connected, this is the default case.
>> -			      But if there are two NOR flashes connected to the
>> -			      bus, you should enable this property.
>> -			      (Please check the board's schematic.)
>> -  - big-endian : That means the IP register is big endian
>> +Required SPI slave node properties:
>> +  - reg: There are two buses (A and B) with two chip selects each.
>> +	 This encodes to which bus and CS the flash is connected:
>> +		<0>: Bus A, CS 0
>> +		<1>: Bus A, CS 1
>> +		<2>: Bus B, CS 0
>> +		<3>: Bus B, CS 1
>>   
>>   Example:
>>   
>> @@ -40,7 +37,7 @@ qspi0: quadspi@...44000 {
>>   	};
>>   };
>>   
>> -Example showing the usage of two SPI NOR devices:
>> +Example showing the usage of two SPI NOR devices on bus A:
>>   
>>   &qspi2 {
>>   	pinctrl-names = "default";
>