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Date: Mon, 24 Sep 2018 18:36:27 +0200
From: Christophe Kerello <christophe.kerello@...com>
To: Miquel Raynal <miquel.raynal@...tlin.com>
CC: <boris.brezillon@...tlin.com>, <richard@....at>,
<dwmw2@...radead.org>, <computersforpeace@...il.com>,
<marek.vasut@...il.com>, <robh+dt@...nel.org>,
<mark.rutland@....com>, <linux-mtd@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linux-stm32@...md-mailman.stormreply.com>
Subject: Re: [PATCH 1/3] dt-bindings: mtd: stm32_fmc2: add STM32 FMC2 NAND
controller documentation
Hi Miquèl,
On 09/22/2018 10:34 AM, Miquel Raynal wrote:
> Hi Christophe,
>
> <christophe.kerello@...com> wrote on Mon, 17 Sep 2018 17:47:38 +0200:
>
>> From: Christophe Kerello <christophe.kerello@...com>
>>
>> This patch adds the documentation of the device tree bindings for the STM32
>> FMC2 NAND controller.
>>
>> Signed-off-by: Christophe Kerello <christophe.kerello@...com>
>> ---
>> .../devicetree/bindings/mtd/stm32-fmc2-nand.txt | 90 ++++++++++++++++++++++
>> 1 file changed, 90 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/mtd/stm32-fmc2-nand.txt
>>
>> diff --git a/Documentation/devicetree/bindings/mtd/stm32-fmc2-nand.txt b/Documentation/devicetree/bindings/mtd/stm32-fmc2-nand.txt
>> new file mode 100644
>> index 0000000..93eaf11
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/mtd/stm32-fmc2-nand.txt
>> @@ -0,0 +1,90 @@
>> +STMicroelectronics Flexible Memory Controller 2 (FMC2)
>> +NAND Interface
>> +
>> +Required properties:
>> +- compatible: "st,stm32mp15-fmc2"
>
> I think this form is preferred:
>
> "
> - compatible: Should be one of:
> * st,stm32mp15-fmc2
> "
Ok, I will modify this comment.
>
>> +- reg: the first contains the register location and length
>
> the register location and length of...?
>
>> + the second contains the data common space used for cs0 and length
>> + the third contains the cmd attribute space used for cs0 and length
>> + the fourth contains the addr attribute space used for cs0 and length
>> + the fifth contains the data common space used for cs1 and length
>> + the sixth contains the cmd attribute space used for cs1 and length
>> + the seventh contains the addr attribute space used for cs1 and length
>
> Maybe you could simplify a bit with something like:
>
> -reg: NAND flash controller memory areas.
> First region ...
> Regions 2 to 4 respectively contain the data, command, and
> address space for CS0.
> Regions 5 to 7 contain the same areas for CS1.
Ok, I will simplify the description of "reg" property.
>
>> +- interrupts: The interrupt number
>> +- pinctrl-0: Standard Pinctrl phandle (see: pinctrl/pinctrl-bindings.txt)
>> +- clocks: Use common clock framework
>> +
>> +Optional properties:
>> +- resets: Reference to a reset controller asserting the FMC controller
>> +- dmas: DMA specifiers (see: dma/stm32-mdma.txt)
>> +- dma-names: Must be "tx", "rx" and "ecc"
>> +
>> +Optional children nodes:
>> +Children nodes represent the available nand chips.
>
> Please s/nand/NAND/ in plain English.
Ok.
>
>> +
>> +Optional properties:
>> +- nand-on-flash-bbt: see nand.txt
>> +- nand-ecc-strength: see nand.txt
>> +- nand-ecc-step-size: see nand.txt
>> +- st,fmc2_timings: array of 8 bytes for NAND timings. The meanings of
>> + these bytes are:
>> + byte 0 TCLR : CLE to RE delay in number of AHB clock cycles, only 4 bits
>> + are valid. Zero means one clock cycle, 15 means 16 clock
>> + cycles.
>> + byte 1 TAR : ALE to RE delay, 4 bits are valid. Same format as TCLR.
>> + byte 2 THIZ : number of HCLK clock cycles during which the data bus is
>> + kept in Hi-Z (tristate) after the start of a write access.
>> + Only valid for write transactions. Zero means 1 cycle,
>> + 255 means 256 cycles.
>> + byte 3 TWAIT : number of HCLK clock cycles to assert the command to the
>> + NAND flash in response to SMWAITn. Zero means 1 cycle,
>> + 255 means 256 cycles.
>> + byte 4 THOLD_MEM : common memory space timing
>> + number of HCLK clock cycles to hold the address (and data
>> + when writing) after the command deassertion. Zero means
>> + 1 cycle, 255 means 256 cycles.
>> + byte 5 TSET_MEM : common memory space timing
>> + number of HCLK clock cycles to assert the address before
>> + the command is asserted. Zero means 1 cycle, 255 means 256
>> + cycles.
>> + byte 6 THOLD_ATT : attribute memory space timing
>> + number of HCLK clock cycles to hold the address (and data
>> + when writing) after the command deassertion. Zero means
>> + 1 cycle, 255 means 256 cycles.
>> + byte 7 TSET_ATT : attribute memory space timing
>> + number of HCLK clock cycles to assert the address before
>> + the command is asserted. Zero means 1 cycle, 255 means 256
>> + cycles.
>
> Let me review the driver but this array of timings is really
> suspicious. I am pretty sure you don't need it in the DT.
"st,fmc2-timings" is an optional property that allow the end user to
overwrite the timings calculated by setup_data_interface callback. By
setting this property in the NAND flash memory device tree node, the end
user could have a better throughput. For NON ONFI SLC NAND, timing mode
0 is often used.
>
>> +
>> +The following ECC strength and step size are currently supported:
>> + - nand-ecc-strength = <1>, nand-ecc-step-size = <512> (HAMMING)
>> + - nand-ecc-strength = <4>, nand-ecc-step-size = <512> (BCH4)
>> + - nand-ecc-strength = <8>, nand-ecc-step-size = <512> (BCH8) (default)
>> +
>> +Example:
>> +
>> + fmc2_nand: fmc2_nand@...02000 {
>> + compatible = "st,stm32mp15-fmc2";
>> + reg = <0x58002000 0x1000>,
>> + <0x80000000 0x1000>,
>> + <0x88010000 0x1000>,
>> + <0x88020000 0x1000>,
>> + <0x81000000 0x1000>,
>> + <0x89010000 0x1000>,
>> + <0x89020000 0x1000>;
>> + interrupts = <GIC_SPI 48 IRQ_TYPE_LEVEL_HIGH>;
>> + clocks = <&rcc FMC_K>;
>> + resets = <&rcc FMC_R>;
>> + pinctrl-names = "default";
>> + pinctrl-0 = <&fmc2_pins_a>;
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> +
>> + nand@0 {
>> + reg = <0>;
>> + nand-on-flash-bbt;
>> + st,fmc2_timings = /bits/ 8 <2 2 1 7 1 0 104 25>;
>> + #address-cells = <1>;
>> + #size-cells = <1>;
>> + };
>> + };
>
> Thanks,
> Miquèl
>
Thanks,
Christophe Kerello.
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