Re: Question about SPI NOR flash

[Sascha Hauer <s.hauer@pengutronix.de>]

On Tue, May 13, 2014 at 10:55:33AM +0200, Holger Schurig wrote:
> Hi,
> 
> my device has an SPI NOR flash Micron N25Q512A13G124F. With the patch
> below it get's detected by barebox and I can at least dump it ("md -s
> /dev/m25p0).
> 
> Before submitting that patch with signed-off, I want however first
> test SPI. It works a but, but only so far:
> 
> barebox:/ unprotect /dev/m25p0
> barebox:/ erase /dev/m25p0
> barebox:/ erase /dev/m25p0.barebox-environment
> barebox:/ saveenv
> saving environment
> could not open /dev/env0: Read-only file system
> saveenv: Read-only file system
> 
> So, what am I missing to connect /dev/env0 by default?
> 
> And, when I do this:
> 
> barebox:/ saveenv /dev/m25p0.barebox-environment
> saving environment
> 
> it seems that it just wrote 00's (before it was FF's, because of the erase):
> 
> barebox:/ md -s /dev/m25p0.barebox-environment
> 00000000: 00000000 00000000 00000000 00000000                ................
> 00000010: 00000000 00000000 00000000 00000000                ................
> 00000020: 00000000 00000000 00000000 00000000                ................
> 00000030: 00000000 00000000 00000000 00000000                ................
> 00000040: 00000000 00000000 00000000 00000000                ................
> 00000050: 00000000 00000000 00000000 00000000                ................
> 00000060: 00000000 00000000 00000000 00000000                ................
> 00000070: 00000000 00000000 00000000 00000000                ................
> 00000080: 00000000 00000000 00000000 00000000                ................
> 00000090: 00000000 00000000 00000000 00000000                ................
> 000000a0: 00000000 00000000 00000000 00000000                ................
> 000000b0: 00000000 00000000 00000000 00000000                ................
> 000000c0: 00000000 00000000 00000000 00000000                ................
> 000000d0: 00000000 00000000 00000000 00000000                ................
> 000000e0: 00000000 00000000 00000000 00000000                ................
> 000000f0: 00000000 00000000 00000000 00000000                ................
> 
> Now, perhaps I must add something to the device tree? When I do ...
> 
> chosen {
>    # ...
>    environment@0 {
>       compatible = "barebox,environment";
>       device-path = &flash, "partname:barebox-environment";
>     };
> };
> 
> &ecspi3 {
>   flash: spiflash@0 {
>     #address-cells = <1>;
>     #size-cells = <1>;
>     compatible = "m25p80";
>     spi-max-frequency = <20000000>;
>     reg = <0>;
> 
>     partition@0 {
>       label = "barebox-environment";
>       reg = <0x0 0x40000>;
>     };
>   };
> };

This looks perfectly fine.

> 
> then I get a backtrace at boot:
> 
> detected i.MX6 Quad revision 1.2
> mdio_bus: miibus0: probed
> m25p80 spiflash@00: mr25h256 (32 Kbytes)

This is your problem. Your device is detected as a 32KB mr25h256 instead
of the n25q512 you really have. Have you seen
http://lists.infradead.org/pipermail/linux-mtd/2014-January/051382.html?

> partition m25p0.barebox-environment not completely inside device m25p0

You define a 256k environment partition in the devicetree, but your
(wrongly detected) device has only 32k.

> unable to handle paging request at address 0xfffffff2

Of course barebox shouldn't crash here, that seems to be a bug.

Sascha

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