Hi, On 12 April 2016 at 21:13, Qianyu Gong <qianyu.g...@nxp.com> wrote: > Hi Simon, > >> -----Original Message----- >> From: s...@google.com [mailto:s...@google.com] On Behalf Of Simon Glass >> Sent: Saturday, April 09, 2016 3:13 AM >> To: Qianyu Gong <qianyu.g...@nxp.com> >> Cc: u-boot@lists.denx.de; Mingkai Hu <mingkai...@nxp.com>; Yao Yuan >> <yao.y...@nxp.com>; jt...@openedev.com >> Subject: Re: A problem about 'sf probe' using DM_SPI >> >> 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 > > Thanks for your explanation. > So you mean the flash messages? Seems that removing the unbind won't affect > reading ID from a real flash.
I don't really understand what you are asking here. > But would the unbind be needed if the dts node is modified at runtime?(I'm > not sure if > it is necessary) You cannot modify the dts node at run-time in U-Boot. It is not currently supported. Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot