[PATCH V2 1/6] drivers: bus: add a new driver for WEIM

? 2013?05?23? 21:09, Arnd Bergmann ??:

OTOH, I agree that it would be nicer if the clk could remain turned
off as long as no children are active. Can we do a clk_disable()
after setting up the timings for the children and then expect those
to actually start up the clk again when they need it?

Or to take things further: would it make sense to represent WEIM
itself as a clock driver and perform the settings for each child
only when it sets up its own clk?

If the child's subsystem supports it, we can do it.

The mtd nand does support this feature, it has @select_chip() hook.
We can enable/disable the clock in the @select_chip().

But the mtd NOR does _not_ supports it.
Please read the /drivers/mtd/maps/physmap_of.c and 
/drivers/mtd/chips/cfi_cmd_set_xxx.c.
Of course, we can add the feature to NOR subsystem. But that's another 
issue.

So the weim should enable the clock all the time now.

I guess it would also make sense to use of_platform_populate() instead
of of_platform_device_create() when creating the children, so we actually

I tried the of_platform_populate(), but failed.

firstly, we should set the timing for the device _before_ we do the 
of_platform_populate().
and i rewrite the weim_parse_dt() to:
------------------------------------------------------------------------------------------
static void weim_parse_dt(struct platform_device *pdev)
{
     struct device_node *child;

     for_each_child_of_node(pdev->dev.of_node, child) {
         if (!child->name)
             continue;

         if (weim_timing_setup(pdev, child)) {
             dev_err(&pdev->dev, "%s set timing failed.\n",
                 child->full_name);
             continue;
         }

     }
     if (!of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev))
         dev_err(&pdev->dev, "%s device create failed.\n",
             child->full_name);
}
------------------------------------------------------------------------------------------

The system hang at :
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

## Booting kernel from Legacy Image at 10800000 ...
    Image Name:   Linux
    Image Type:   ARM Linux Kernel Image (uncompressed)
    Data Size:    4259851 Bytes =  4.1 MB
    Load Address: 10008000
    Entry Point:  10008000
    Verifying Checksum ... OK
    Loading Kernel Image ... OK
OK

Starting kernel ...
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++==



thanks
Huang Shijie