Hi Qianyu,
On 25 March 2016 at 03:34, Qianyu Gong <qianyu.g...@nxp.com> wrote:
> Hi Simon,
>
>
>
> I think I’m not very clear with this code in common/cmd_sf.c:
>
> “
>
> # ifdef CONFIG_DM_SPI_FLASH
>
> /* Remove the old device, otherwise probe will just be a nop */
>
> ret = spi_find_bus_and_cs(bus, cs, &bus_dev, &new);
>
> if (!ret) {
>
> device_remove(new);
>
> device_unbind(new);
>
> }
>
> ”
>
> I may understand the remove but why need to unbind the device?
This is because otherwise 'sf probe' would be a nop if the device
already existed. The spi_flash_probe_bus_cs() call will simply return
the existing device. If something has changed on the bus, it would be
ignored.
>
> The unbind would cause a series of free operations on the device list,
> correct?
Yes
>
>
>
> Then if I probe a flash twice, at the second time the driver model will
> create
>
> a new flash named ‘spi_flash@xx:xx’ using default settings because it
> doesn’t
>
> find such a device in the device list and never probes it from the board’s
> fdt again.
Yes.
>
>
>
> => dm tree
>
> Class Probed Name
>
> ----------------------------------------
>
> root [ + ] root_driver
>
> simple_bus [ + ] `-- soc
>
> spi [ + ] |-- dspi@2100000
>
> spi_flash [ ] | |-- n25q128a
>
> spi_flash [ + ] | |-- spi_flash@1:1
>
> spi_flash [ + ] | `-- spi_flash@1:2
>
>
>
> Fortunately the default SPI mode set by U-Boot is SPI_MODE_3 so it doesn’t
> cause
>
> issues on our boards. But if an SPI flash which only supports SPI_MODE_0 is
> used,
>
> I think it wouldn’t work properly from the second probe.
>
>
>
>
>
> Sorry if there is something wrong with my understandings.
>
> Just because I found my flash’s name was changed to spi-flash@xx:xx in dm
> tree
>
> after several probes, I began to read something about driver model.J
Yes I think removing the unbind would be OK, except that we need a way
to show the messages at the end of spi_flash_scan().
Probably these messages should move out of the uclass and into a
separate call. We could add a function like spi_flash_show(struct
udevice *dev) and call it from do_spi_flash_probe() and perhaps
saveenv().
Regards,
Simon
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