On 24 November 2015 at 14:59, Simon Falsig <[email protected]> wrote: >>On 20 November 2015 at 19:13, Simon Falsig <[email protected]> wrote: >>> I have a custom board based on a TI AM3356 processor (quite similar to >>> a BeagleBone) with an Everspin MR25H256 MRAM attached to the SPI bus, >>> currently using U-Boot 2015.10 to boot a 3.18.9-rt5 Linux kernel. >>> >>> I'd like to use this MRAM to store the MAC address for one of the >>> Ethernet interfaces, but I'm having a bit of trouble getting started >>> on how support for this should be added. >>> >>> I can access the MRAM just fine from Linux (using the m25p80 driver >>> and the MTD framework), so with the appropriate drivers compiled into >>> the kernel, Linux picks the chip up without any issue by simply adding >>> the following to the device tree: >>> >>> mram: m25p80@0 { >>> #address-cells = <1>; >>> #size-cells = <1>; >>> compatible = "mr25h256"; >>> reg = <0>; >>> spi-max-frequency = <40000000>; >>> status = "okay"; >>> }; >>> >>> I'd like U-Boot to do something similar, but there are a few issues: >>> 1. The chip is not JEDEC compatible, so it cannot be probed like >>> the other chips currently listed in drivers/mtd/spi/sf_params.c >>> 2. Since it's an MRAM, it doesn't need to be erased before being >>> written - Linux has a flag for this, but it doesn't seem as if >>> U-Boot has anything similar. (Not that I need this currently >>> though, as I only need to be able to read the chip for now - but >>> it'd be nice to have, and others might be able to use it too.) >>> >> >>Thanks for your concerns, It's been very clear. >> >>> I've tried having a look at doc/driver-model/spi-howto.txt, hoping >>> that this would have up-to-date information on how to implement/modify >>> a SPI driver, but when I for instance look at spi_setup_slave_fdt(), >>> which seems to be one of the necessary functions, I can only find it >>> implemented in drivers/spi/spi-uclass.c, with a comment saying that it >>> is only for compatibility, and that it is to be removed?... >> >>These are spi drivers not related to spi-flash. >>drivers/mtd/spi/sf_probe.c >>drivers/mtd/spi/sf_ops.c are spi-flash related. >> >>If possible you can add non-jedec things to sf_probe.c similar way as >>Linux, BTW I'm >currently working spi-flash subsystem which should as >>modular as Linux[1]. I hope we may >get that version coming releases, but >>what ever is feasible to you just work on that I >would help you always. >> >>> >>> If anyone can help me with a few hints on how to get started adding >>> support for this chip, it'd be much appreciated! >>> >>> Thanks in advance and best regards, >> >>[1] >>http://git.denx.de/?p=u-boot/u-boot-spi.git;a=shortlog;h=refs/heads/spi-nor-mtd > > Thanks for the hints! I'll have a look at the existing files and your tree, > and see if I can find a good way to do this.
Try to add on top of this new tree [1] which is similar to Linux. [1] http://git.denx.de/?p=u-boot/u-boot-spi.git;a=shortlog;h=refs/heads/spi-nor -- Jagan. _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
