Re: mtd, nand, omap2: parse cmdline partition fail

Frans Klaver
2015-12-04T07:17:20Z

On Fri, Dec 4, 2015 at 7:48 AM, Heiko Schocher <hs@denx.de> wrote:
> Hello Frans,
>
> I just tried current mainline kernel:
> commit 2255702db4014d1c69d6037ed7bdad2d2e271985
> Merge: 9e5d25e c86576e
> Author: Linus Torvalds <torvalds@linux-foundation.org>
> Date: Mon Nov 30 16:06:44 2015 -0800
>
> Merge tag 'mn10300-for-linus-v4.4-rc4' of
> git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging
>
> on an am3517 based board (mainlining soon). And with your commit:
> commit 853f1c58c4b2: mtd: nand: omap2: show parent device structure in sysfs
>
> MTD partitions from cmdline are not longer detected:
>
> [ 2.087305] nand: device found, Manufacturer ID: 0x2c, Chip ID: 0xcc
> [ 2.094097] nand: Micron MT29F4G16ABADAWP
> [ 2.098303] nand: 512 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB
> size: 64
> [ 2.106296] nand: WARNING: MT29F4G16ABADAWP: the ECC used on your system
> is too weak compared to the one required by the NAND chip
> [ 2.118674] MT29F4G16ABADAWP: 'partitions' subnode not found on
> /ocp/gpmc@6e000000/nand@0,0. Trying to parse direct subnodes as partitions.
> [...]
>
> before this patch it worked:
> [ 2.307444] nand: device found, Manufacturer ID: 0x2c, Chip ID: 0xcc
> [ 2.314092] nand: Micron MT29F4G16ABADAWP
> [ 2.318348] nand: 512 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB
> size: 64
> [ 2.326331] nand: WARNING: omap2-nand.0: the ECC used on your system is
> too weak compared to the one required by the NAND chip
> [ 2.338336] 5 cmdlinepart partitions found on MTD device omap2-nand.0
> [ 2.345129] Creating 5 MTD partitions on "omap2-nand.0":
> [ 2.350704] 0x000000000000-0x000000080000 : "MLO"
> [ 2.366877] 0x000000080000-0x000000180000 : "u-boot"
> [ 2.379179] 0x000000180000-0x0000001c0000 : "env1"
> [ 2.390627] 0x0000001c0000-0x000000200000 : "env2"
> [ 2.402255] 0x000000200000-0x000020000000 : "common_data"
>
> Reason is taht the mtd->name has changed from "omap2-nand.0" to the
> nand chip name ...
>
> If I revert this part from the patch
>
> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
> index 93f664c..28dcf66 100644
> --- a/drivers/mtd/nand/omap2.c
> +++ b/drivers/mtd/nand/omap2.c
> @@ -1685,6 +1685,7 @@ static int omap_nand_probe(struct platform_device
> *pdev)
> info->ecc_opt = pdata->ecc_opt;
> mtd = &info->mtd;
> mtd->priv = &info->nand;
> + mtd->name = dev_name(&pdev->dev);
> mtd->dev.parent = &pdev->dev;
> nand_chip = &info->nand;
> nand_chip->ecc.priv = NULL;
>
> It works again ...
>
> So the question is, is it intended to change the "mtd->name"?

That's definitely not intended. The expectation with this patch is
that nothing really changes, except that a parent device link is
available in sysfs. For the name this patch depends on 807f16d4db956
("mtd: core: set some defaults when dev.parent is set") which does
something like:

if (mtd->dev.parent) {
if (!mtd->name)
mtd->name = dev_name(mtd->dev.parent);
}

The fact that this produces different names for you is slightly
surprising to me, unless mtd->name is already set to something by the
time it reaches add_mtd_device(). Or I overlooked something, which is
entirely plausible as well.

So effectively this should be the same as doing:

mtd->dev.parent = &pdev->dev;
mtd->name = dev_name(mtd->dev.parent);

> But wondering, if there are two or more identical nand chips in the
> system, they will have the same mtd->name ... which seems buggy to me...

Agree.

Thanks,
Frans