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SubjectRe: [PATCH 1/6] drivers: bus: add a new driver for WEIM
于 2013年05月20日 21:18, Sascha Hauer 写道:
> On Mon, May 20, 2013 at 04:48:57PM +0800, Huang Shijie wrote:
>> weim-cs-index.
>> +
>> +Example for an i.MX6q-sabreauto board:
>> + weim: weim@021b8000 {
>> + 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?
Must be set to 2 to allow memory address translation.
>> + #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@40000 {
>> + label = "U-Boot-ENV";
>> + reg =<0x40000 0x10000>;
>> + read-only;
>> + };
>> +
>> + partition@50000 {
>> + label = "Kernel";
>> + reg =<0x50000 0x3b0000>;
>> + };
> The partitions are unnecessary to understand the example. Please drop them.
okay.
>> +#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)
>
yes.
>> + 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?
>
>
yes. We need this clock.

in actually, this clock is just a clock gate for several clocks,
including clock for register access, and
other necessary clocks.

thanks
Huang Shijie
.






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