On Fri, Jun 24, 2011 at 4:26 PM, Wolfgang Denk wd@denx.de wrote:
Dear =?ISO-8859-1?Q?Frank_Svendsb=F8e?=,
In message BANLkTimt0LYXr-B5PAr1ONEaEoWKCyEHbw@mail.gmail.com you wrote:
Hi Wolfgang, I did as you recommended and replaced cfi-flash with mtd-ram in the device tree. I also defined CONFIG_MTD_PHYSMAP_OF, CONFIG_MTD_MTDRAM, CONFIG_MTDRAM_TOTAL_SIZE according to our specifications. The default erase-size was 128k, which is what we have too, so I didn't touch that. Now when I boot the kernel recognizes all the partitions I've defined in the dts. But, when mounting a jffs2-filesystem, it ends with a jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found...
Do you have any other tips?
Difficult to speculate - I don't know your hardware (eventually you have two 16 bit flash chips in parallel to build a 32 bit bus, and have to double the chip's erase block size?), and I don;t know how you created the JFFS2 file system.
Yes I know, and I don't expect you to find the answer based on so little data. FYI: We have two flash chips yes, but not to build a 32-bit bus, we have two for redundancy issues (one is storing a factory default version). 16 bits databus and each sector is 64k words, ie. 128k bytes. I created the jffs2 images using ELDKs mkfs.jffs2. Thanks for providing me this tool :)
Are you sure you want to use JFFS2? UBIFS is considered to be a better choice these days...
No, not sure. I've got two reasons for staying with JFFS2. 1) We normally don't write to flash except when upgrading, so flash performance/duration isn't very critical 2) I discovered UBIFS after I had JFFS2 working and haven't seen the real need for it yet.
When working with this, I realised that if I could get it to work we'd still might have a problem. You see, we need write access for one of the flashes when upgrading software. We can't treat this as a simple ROM. So do we need CFI working in order to set the device into write-mode, erase flash sectors, etc.? Or do mtd-ram handle flash write operations too?
mtd-ram provides a pure memory interface, i. e. you cannot use this to erase or program any blocks in a CFI flash device. To do so, you need the CFI driver.
Right. mtd-ram is thus a dead-end solution for our purpose. We need to be able to write in some specific cases.
In theory, I guess I could unmount the root fs, unload the mtd module, insert the cfi-flash module, mount the filesystem, then write, etc..
Yes, or you could start with the CFI driver in the first place.
That's what I did before you started interrupting me about mtd-ram... No, just kidding :-)
Did you mean I should adapt the general CFI driver to support our configuration, or... Based on what you say below I'm not sure what you actually mean.
But isn't that harder than write a custom map driver?
I consider your chances to get such a customdriver into mainline to be epsilon. And you don't really want to use any out of tree drivers.
Me too. Small chances. So we have two options I guess: 1) Ditch hardware write protection and use CFI as it is supposed to be used, or 2) write a custom out-of-tree driver. What would you go for?
I'll consider if and how to get things into mainline once we have things working as we want. If my port isn't accepted I will at least learn why. Maybe the next will :)
Best regards, Frank