Re: [PATCH 1/3] dt-bindings: mtd: stm32_fmc2: add STM32 FMC2 NAND controller documentation
From: Christophe Kerello
Date: Mon Sep 24 2018 - 12:37:57 EST
Hi MiquÃl,
On 09/22/2018 10:34 AM, Miquel Raynal wrote:
Hi Christophe,
<christophe.kerello@xxxxxx> wrote on Mon, 17 Sep 2018 17:47:38 +0200:
From: Christophe Kerello <christophe.kerello@xxxxxx>
This patch adds the documentation of the device tree bindings for the STM32
FMC2 NAND controller.
Signed-off-by: Christophe Kerello <christophe.kerello@xxxxxx>
---
.../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@58002000 {
+ 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,
MiquÃl
Thanks,
Christophe Kerello.