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Date: Mon, 20 May 2013 15:18:27 +0200
From: Sascha Hauer <s.hauer@...gutronix.de>
To: Huang Shijie <b32955@...escale.com>
Cc: grant.likely@...aro.org, devicetree-discuss@...ts.ozlabs.org,
linux-kernel@...r.kernel.org, rob.herring@...xeda.com,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/6] drivers: bus: add a new driver for WEIM
On Mon, May 20, 2013 at 04:48:57PM +0800, Huang Shijie wrote:
> The WEIM(Wireless External Interface Module) works like a bus.
> You can attach many different devices on it, such as NOR, onenand.
>
> In the case of i.MX6q-sabreauto, the NOR is connected to WEIM.
>
> This patch also adds the devicetree binding document.
> The driver only works when the devicetree is enabled.
>
> Signed-off-by: Huang Shijie <b32955@...escale.com>
> ---
> Documentation/devicetree/bindings/bus/imx-weim.txt | 69 +++++++++
> drivers/bus/Kconfig | 9 ++
> drivers/bus/Makefile | 1 +
> drivers/bus/imx-weim.c | 145 ++++++++++++++++++++
> 4 files changed, 224 insertions(+), 0 deletions(-)
> create mode 100644 Documentation/devicetree/bindings/bus/imx-weim.txt
> create mode 100644 drivers/bus/imx-weim.c
>
> diff --git a/Documentation/devicetree/bindings/bus/imx-weim.txt b/Documentation/devicetree/bindings/bus/imx-weim.txt
> new file mode 100644
> index 0000000..9913454
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/bus/imx-weim.txt
> @@ -0,0 +1,69 @@
> +Device tree bindings for i.MX Wireless External Interface Module (WEIM)
> +
> +The term ???wireless??? does not imply that the WEIM is literally an interface
> +without wires. It simply means that this module was originally designed for
> +wireless and mobile applications that use low-power technology.
> +
> +The actual devices are instantiated from the child nodes of a WEIM node.
> +But now we only have the NOR device.
> +
> +NOR flash connected to the WEIM (found on i.MX boards) are represented as
> +child nodes with a name of "nor".
> +
> +Required properties:
> +
> + - compatible: Should be set to "fsl, imx6q-weim"
> + - reg: A resource specifier for the register space
> + (see the example below)
> + - interrupts: the interrupt number, see the example below.
> + - clocks: the clock, see the example below.
> + - #address-cells: Must be set to 2 to allow memory address translation
> + - #size-cells: Must be set to 1 to allow CS address passing
> + - ranges: Must be set up to reflect the memory layout with four
> + integer values for each chip-select line in use:
> +
> + <cs-number> 0 <physical address of mapping> <size>
> +
> +Timing properties for child nodes. All are mandatory, not optional.
> +
> + -weim-cs-index: The CS index which the device is attaching on.
> + -weim-cs-timing: The timing array, contains 6 timing values for the
> + weim-cs-index.
> +
> +Example for an i.MX6q-sabreauto board:
> + weim: weim@...b8000 {
> + compatible = "fsl,imx6q-weim";
> + reg = <0x021b8000 0x4000>;
> + interrupts = <0 14 0x04>;
> + clocks = <&clks 196>;
> + #address-cells = <2>;
Why is address cells 2 in this example?
> + #size-cells = <1>;
> + ranges = <0 0 0x08000000 0x08000000>;
> +
> + nor@0,0 {
> + compatible = "cfi-flash";
> + reg = <0 0 0x02000000>;
> + #address-cells = <1>;
> + #size-cells = <1>;
> + bank-width = <2>;
> +
> + weim-cs-index = <0>;
> + weim-cs-timing = <0x00620081 0x00000001 0x1C022000
> + 0x0000C000 0x1404a38e 0x00000000>;
> + partition@0 {
> + label = "U-Boot";
> + reg = <0x0 0x40000>;
> + };
> +
> + partition@...00 {
> + label = "U-Boot-ENV";
> + reg = <0x40000 0x10000>;
> + read-only;
> + };
> +
> + partition@...00 {
> + label = "Kernel";
> + reg = <0x50000 0x3b0000>;
> + };
The partitions are unnecessary to understand the example. Please drop them.
> +#define CS_TIMING_LEN 6
> +#define CS_REG_RANGE 0x18
> +/* Parse and set the timing for this device. */
> +static int weim_timing(struct platform_device *pdev, struct device_node *np)
> +{
> + struct imx_weim *weim = platform_get_drvdata(pdev);
> + u32 value[CS_TIMING_LEN];
> + u32 cs_idx;
> + int ret;
> + int i;
> +
> + ret = of_property_read_u32(np, "weim-cs-index", &cs_idx);
> + if (ret)
> + goto weim_parse_err;
It would be nice to check for cs_idx being valid.
> +
> + ret = of_property_read_u32_array(np, "weim-cs-timing",
> + value, CS_TIMING_LEN);
> + if (ret)
> + goto weim_parse_err;
> +
> + /* set the timing for WEIM */
> + for (i = 0; i < CS_TIMING_LEN; i++)
> + writel(value[i], weim->base + cs_idx * CS_REG_RANGE + i * 4);
> + return 0;
> +
> +weim_parse_err:
> + return ret;
> +}
> +
> +static int weim_parse_dt(struct platform_device *pdev)
> +{
> + struct device_node *child;
> + int ret;
> +
> + /* We only support the Parallel NOR now. We may add more in future. */
> + child = of_find_node_by_name(NULL, "nor");
> + if (child) {
> + ret = weim_timing(pdev, child);
> + if (ret)
> + goto parse_fail;
> +
> + if (!of_platform_device_create(child, NULL, &pdev->dev)) {
> + ret = -EINVAL;
> + goto parse_fail;
> + }
> + }
What you want to do here is:
- iterate over your child nodes
- call weim_timing() for each of them
- call of_platform_device_create for each child (or even
of_platform_populate() with the parent node)
> + return 0;
> +
> +parse_fail:
> + return ret;
> +}
> +
> +static int weim_probe(struct platform_device *pdev)
> +{
> + struct imx_weim *weim;
> + struct resource *res;
> + int ret = -EINVAL;
> +
> + weim = devm_kzalloc(&pdev->dev, sizeof(*weim), GFP_KERNEL);
> + if (!weim) {
> + ret = -ENOMEM;
> + goto weim_err;
> + }
> + platform_set_drvdata(pdev, weim);
> +
> + /* get the resource */
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res) {
> + ret = -ENOENT;
> + goto weim_err;
> + }
No need to do error checking here. devm_ioremap_resource() will do this
for you and also print an error message.
> +
> + weim->base = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(weim->base)) {
> + ret = PTR_ERR(weim->base);
> + goto weim_err;
> + }
> +
> + /* get the clock */
> + weim->clk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(weim->clk))
> + goto weim_err;
> +
> + clk_prepare_enable(weim->clk);
what is this clock used for? Is it necessary for the register access or
is it necessary for the chipselects on the WEIM to work?
Sascha
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