Re: [PATCH v3 06/11] memory: atmel-ebi: add DT bindings documentation

[Boris Brezillon]

On Wed, 3 Dec 2014 16:15:36 +0100
Nicolas Ferre <nicolas.ferre@xxxxxxxxx> wrote:

> Le 03/12/2014 15:56, Nicolas Ferre a Ãcrit :
> > Le 01/12/2014 11:27, Boris Brezillon a Ãcrit :
> >> The EBI (External Bus Interface) is used to access external peripherals
> >> (NOR, SRAM, NAND, and other specific devices like ethernet controllers).
> >> Each device is assigned a CS line and an address range and can have its
> >> own configuration (timings, access mode, bus width, ...).
> >> This driver provides a generic DT binding to configure a device according
> >> to its requirements.
> >> For specific device controllers (like the NAND one) the SMC timings
> >> should be configured by the controller driver through the matrix and smc
> >> syscon regmaps.
> >>
> >> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>
> >> ---
> >>  .../bindings/memory-controllers/atmel-ebi.txt      | 155 +++++++++++++++++++++
> >>  1 file changed, 155 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/memory-controllers/atmel-ebi.txt
> >>
> >> diff --git a/Documentation/devicetree/bindings/memory-controllers/atmel-ebi.txt b/Documentation/devicetree/bindings/memory-controllers/atmel-ebi.txt
> >> new file mode 100644
> >> index 0000000..3749ea1
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/memory-controllers/atmel-ebi.txt
> >> @@ -0,0 +1,155 @@
> >> +* Device tree bindings for Atmel EBI
> >> +
> >> +The External Bus Interface (EBI) controller is a bus where you can connect
> >> +asynchronous (NAND, NOR, SRAM, ....) and synchronous memories (SDR/DDR SDRAMs).
> >> +The EBI provides a glue-less interface to asynchronous memories though the SMC
> >> +(Static Memory Controller).
> >> +Synchronous memories (and some asynchronous memories like NANDs) can be
> >> +attached to specialized controllers which are responsible for configuring the
> >> +bus appropriately according to the connected device.
> >> +In the other hand, the bus interface can be automated for simple asynchronous
> >> +devices.
> >> +
> >> +Required properties:
> >> +
> >> +- compatible:		"atmel,at91sam9260-ebi"
> >> +			"atmel,at91sam9261-ebi"
> >> +			"atmel,at91sam9263-ebi0"
> >> +			"atmel,at91sam9263-ebi1"
> > 
> > Ditto: 9263 twice.
> > 
> >> +			"atmel,at91sam9g45-ebi"
> >> +			"atmel,at91sam9x5-ebi"
> >> +			"atmel,sama5d3-ebi"
> >> +
> >> +- reg:			Contains offset/length value for EBI memory mapping.
> >> +			This property might contain several entries if the EBI
> >> +			memory range is not contiguous
> >> +
> >> +- #address-cells:	Must be 2.
> >> +			The first cell encodes the CS.
> >> +			The second cell encode the offset into the CS memory
> >> +			range.
> >> +
> >> +- #size-cells:		Must be set to 1.
> >> +
> >> +- ranges:		Encodes CS to memory region association.
> >> +
> >> +- clocks:		Clock feeding the EBI controller.
> >> +			See clock-bindings.txt
> >> +
> >> +Child chip-select (cs) nodes contain the memory devices nodes connected to
> >> +such as NOR (e.g. cfi-flash) and NAND.
> >> +There might be board specific devices like FPGAs.
> >> +You'll define you device requirements in these child nodes.
> >> +
> >> +Required child cs node properties:
> >> +
> >> +- #address-cells:	Must be 2.
> >> +
> >> +- #size-cells:		Must be 1.
> >> +
> >> +- ranges:		Empty property indicating that child nodes can inherit
> >> +			memory layout.
> >> +
> >> +Optional child cs node properties:
> >> +- atmel,generic-dev		boolean property specifying if the device is
> >> +				a generic device.
> 
> Well... no real information, specify right here what a "generic device" is.

I do not describe what a generic device is, but the description of a
specialized device is given just below.

Maybe I haven't chosen the appropriate word here.
The datasheet gives the following description:


> 
> >> +				The following properties are only parsed if
> >> +				this property is present.
> >> +				Specialized devices are attached to specialized
> >> +				controllers which are responsible for
> >> +				configuring the bus appropriately.
> >> +				Here are some examples of specialized
> >> +				controllers: NAND, CompactFlash, SDR-SDRAM.
> >> +
> >> +- atmel,bus-width:		width of the asynchronous device's data bus
> >> +				8, 16 or 32.
> >> +				8 if not present.
> >> +
> >> +- atmel,byte-access-type	"write" or "select" (see Atmel datasheet).
> >> +				"select" if not present.
> >> +
> >> +- atmel,read-mode		"nrd" or "ncs".
> >> +				"ncs" is not present.
> >> +
> >> +- atmel,write-mode		"nwe" or "ncs".
> >> +				"ncs" is not present.
> >> +
> >> +- atmel,exnw-mode		"disabled", "frozen" or "ready".
> >> +				"disabled" if not present.
> >> +
> >> +- atmel,page-mode		enable page mode if present. The provided value
> >> +				defines the page size (supported values: 4, 8,
> >> +				16 and 32).
> >> +
> >> +Optional device timings expressed in nanoseconds (if the property is not
> >> +present 0 is assumed):
> >> +
> >> +- atmel,ncs-rd-setup-ns
> >> +- atmel,nrd-setup-ns
> >> +- atmel,ncs-wr-setup-ns
> >> +- atmel,nwe-setup-ns
> >> +- atmel,ncs-rd-pulse-ns
> >> +- atmel,nrd-pulse-ns
> >> +- atmel,ncs-wr-pulse-ns
> >> +- atmel,nwe-pulse-ns
> >> +- atmel,nwe-cycle-ns
> >> +- atmel,nrd-cycle-ns
> >> +- atmel,tdf-ns
> >> +
> >> +- atmel,tdf-optimized		data float optimized mode. If present the data
> >> +				float time is optimized depending on the next
> >> +				device being accessed (next device setup
> >> +				time is substracted to the current devive data
> > 
> > Typo: subtract, device
> > 
> >> +				float time).
> >> +
> >> +
> >> +
> >> +Example:
> >> +
> >> +	ebi: ebi@10000000 {
> >> +		compatible = "atmel,sama5d3-ebi", "simple-bus";
> >> +		#address-cells = <2>;
> >> +		#size-cells = <1>;
> >> +		atmel,smc = <&hsmc>;
> >> +		atmel,matrix = <&matrix>;
> >> +		reg = <0x10000000 0x10000000
> >> +		       0x40000000 0x30000000>;
> >> +		ranges = <0x0 0x0 0x10000000 0x10000000
> >> +			  0x1 0x0 0x40000000 0x10000000
> >> +			  0x2 0x0 0x50000000 0x10000000
> >> +			  0x3 0x0 0x60000000 0x10000000>;
> >> +		clocks = <&mck>;
> >> +
> >> +		pinctrl-names = "default";
> >> +		pinctrl-0 = <&pinctrl_ebi_addr>;
> >> +
> >> +		cs@0 {
> >> +			#address-cells = <2>;
> >> +			#size-cells = <1>;
> >> +			ranges;
> >> +			atmel,generic-dev;
> >> +			atmel,read-mode = "nrd";
> >> +			atmel,write-mode = "nwe";
> >> +			atmel,bus-width = <16>;
> >> +			atmel,ncs-rd-setup-ns = <0>;
> >> +			atmel,ncs-wr-setup-ns = <0>;
> >> +			atmel,nwe-setup-ns = <8>;
> >> +			atmel,nrd-setup-ns = <16>;
> >> +			atmel,ncs-rd-pulse-ns = <84>;
> >> +			atmel,ncs-wr-pulse-ns = <84>;
> >> +			atmel,nrd-pulse-ns = <76>;
> >> +			atmel,nwe-pulse-ns = <76>;
> >> +			atmel,nrd-cycle-ns = <107>;
> >> +			atmel,nwe-cycle-ns = <84>;
> >> +			atmel,tdf-ns = <16>;
> >> +
> >> +			nor: flash@0,0 {
> >> +				compatible = "cfi-flash";
> >> +				#address-cells = <1>;
> >> +				#size-cells = <1>;
> >> +				reg = <0x0 0x0 0x1000000>;
> >> +				bank-width = <2>;
> >> +			};
> >> +		};
> >> +	};
> >> +
> >>
> > 
> > 
> 
> 



-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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