[U-Boot] [RFC PATCH 17/20] cmd: mtd: add 'mtd' command

[Boris Brezillon <boris.brezillon@bootlin.com>]

On Wed, 11 Jul 2018 15:51:39 +0200
Miquel Raynal <miquel.raynal@bootlin.com> wrote:

> > > +
> > > +	argc -= 3;
> > > +	argv += 3;
> > > +
> > > +	/* Do the parsing */
> > > +	if (!strncmp(cmd, "read", 4) || !strncmp(cmd, "write", 5)) {
> > > +		bool read, raw, woob;
> > > +		uint *waddr = NULL;
> > > +		u64 off, len;
> > > +
> > > +		read = !strncmp(cmd, "read", 4);
> > > +		raw = strstr(cmd, ".raw");
> > > +		woob = strstr(cmd, ".oob");
> > > +
> > > +		if (!read) {
> > > +			if (argc < 1)
> > > +				return CMD_RET_USAGE;
> > > +
> > > +			waddr = map_sysmem(simple_strtoul(argv[0], NULL, 10),
> > > +					   0);
> > > +			argc--;
> > > +			argv++;
> > > +		}
> > > +
> > > +		off = argc > 0 ? simple_strtoul(argv[0], NULL, 10) : 0;
> > > +		len = argc > 1 ? simple_strtoul(argv[1], NULL, 10) :
> > > +				 mtd->writesize + (woob ? mtd->oobsize : 0);
> > > +
> > > +		if ((u32)off % mtd->writesize) {
> > > +			printf("Section not page-aligned (0x%x)\n",
> > > +			       mtd->writesize);
> > > +			return -EINVAL;
> > > +		}
> > > +
> > > +		if (woob && (len != (mtd->writesize + mtd->oobsize))) {
> > > +			printf("OOB operations are limited to single pages\n");
> > > +			return -EINVAL;
> > > +		}    
> > 
> > Is this a uboot limitation? I don't think you have such a limitation in
> > Linux.  
> 
> Kind of, only one single page write with OOB at a time is possible
> says a comment on mtd_oob_ops in mtd.h in Linux. Reads are actually not
> limited. But I really prefer to keep this limitation that simplifies _a
> lot_ the logic and is not really useful to a u-boot user I suppose.

It is useful when you write things in raw mode and the image you write
contains OOB (which in turn contains pre-generated ECC bytes). I know we
do such things on sunxi when writing the SPL.

> 
> >   
> > > +
> > > +		if ((off + len) >= mtd->size) {    
> > 
> > That doesn't work when reading the last page of the MTD device with
> > woob = true. See how Linux handle that here [1]. BTW, why don't you let
> > mtdcore.c do these checks for you (that's also true for unaligned
> > accesses)?  
> 
> Because the relevant patch (and its fix :) ) has not been backported
> yet.
> 
> And now I understand your voice in my ears "do it".

Hehe. So I guess I'll see this patch in your v2 :-).