Messages in this thread | | | Date | Mon, 13 Jan 2014 10:02:46 +0100 | From | boris brezillon <> | Subject | Re: [linux-sunxi] Re: [RFC PATCH 0/9] mtd: nand: add sunxi NAND Flash Controller support |
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Hi Henrik,
On 11/01/2014 22:11, Henrik Nordström wrote: > <bbrezillon> thanks for pointing out your documents > <bbrezillon> I'm trying to get the NAND driver with HW ECC (and HW RND) > without using DMA at all > > I tried many things but did not quite get the ECC reading command to > return meaningful resuts. But should work somehow. > > <bbrezillon> do you have any other information I could use to do this ? > > Not really. There is no known code to look at using the nand controller > without DMA. All allwinner code uses DMA even the boot ROM (BROM). > > <bbrezillon> For example, I wonder why there are 2 RAM sectors (the > driver I found only make use of RAM0) > > I think it's used during DMA to fetch next sector while the previous one > is transferred by DMA. But not sure.
Some feedback on my tests:
- I managed to get HW ECC working without any DMA transfer (using CMD = 01): * I only tested the sequential ECC => ECC are stored between 2 data blocks (1024 byte) * Non sequential ECC should work if I store ECC bytes in the OOB area too (I'll just have to send RANDOM_OUT commands to move to the OOB area before sending the ECC cmd and another RANDOM_OUT to go back to the DATA area)
- The HW RND (randomizer) works too, I'll just have to figure out how this could be mainlined: * using a simple dt property to tell the controller it should enable the randomizer * provide an interface (like the nand_ecc_ctrl struct ) for other to add their own randomizer implementation (this was requested: https://lkml.org/lkml/2013/12/13/154)
The most complicated part is the boot0 partition.
Tell me if I'm wrong, but here's what I understood from your work (and yuq's work too):
boot 0 part properties: - uses sequential ECC - uses 1024 bytes ECC blocks - boot0 code is stored only on the first ECC block of each page (1024 bytes + ecc bytes) - boot0 code is stored on the first 64 pages of the first block - boot0 uses HW randomizer with a specific rnd seed (0x4a80)
It's not that complicated to read/write from/to boot0, but it's a bit more to mainline this implementation: - the nand chip must use the same ECC algorithm and ECC layout on the whole flash (no partition specific config available) - you cannot mark some part of pages as unused => the nand driver will write the whole page, not just the first ECC block (1024 bytes)
I thought about manually creating an mtd device that fullfils these needs (in case we encounter the "allwinner,nandn-boot" property on a nand@X node), but I'm not sure this is the right approach.
Any ideas ?
Best Regards,
Boris > > Regards > Henrik >
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