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Date: Fri, 7 Nov 2014 09:21:39 -0600
From: Rob Herring <robherring2@...il.com>
To: Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc: Samuel Ortiz <sameo@...ux.intel.com>,
Lee Jones <lee.jones@...aro.org>,
Nicolas Ferre <nicolas.ferre@...el.com>,
Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
Andrew Victor <linux@...im.org.za>,
Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Tomeu Vizoso <tomeu.vizoso@...labora.com>,
Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 06/11] memory: atmel-ebi: add DT bindings documentation
On Wed, Nov 5, 2014 at 10:01 AM, Boris Brezillon
<boris.brezillon@...e-electrons.com> wrote:
> Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
Perhaps some commit msg?
While this binding seems mostly okay to me, this is the 2nd memory
controller binding I've looked at in the last day [1]. There are
probably some others already as well. This makes me think we need a
generic binding here. At least the node structure and how we define
chip selects should be common.
While I like timing information in time units over magic register
values in the Tegra binding, the reality is converting timing info to
register values is generally very hard to get both correct and
optimal. In the end, you probably need to hand tweak the register
settings anyway. So I'm hesitant to say it must be done 1 way here.
Rob
[1] http://lwn.net/Articles/618466/
> ---
> .../bindings/memory-controllers/atmel-ebi.txt | 153 +++++++++++++++++++++
> 1 file changed, 153 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..dc2c34f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/memory-controllers/atmel-ebi.txt
> @@ -0,0 +1,153 @@
> +* 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"
> + "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.
> + The following properties are only parsed if
> + this property is present.
> + Specialized devices are attached to specialized
> + controllers which should configure the bus
> + appropriately.
> +
> +- 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
> + float time).
> +
> +
> +
> +Example:
> +
> + ebi: ebi@...00000 {
> + 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>;
> + };
> + };
> + };
> +
> --
> 1.9.1
>
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