Thread (37 messages) 37 messages, 4 authors, 2018-05-31

[PATCH 6/9] ARM: dts: wheat: Drop MTD partitioning from DT

From: Marek Vasut <hidden>
Date: 2018-05-30 10:13:31
Also in: linux-devicetree, linux-renesas-soc

On 05/28/2018 11:36 AM, Simon Horman wrote:
On Mon, May 28, 2018 at 10:54:57AM +0200, Geert Uytterhoeven wrote:
quoted
Hi Simon,

On Mon, May 28, 2018 at 10:41 AM, Simon Horman [off-list ref] wrote:
quoted
On Thu, May 24, 2018 at 04:52:59PM +0200, Marek Vasut wrote:
quoted
On 05/23/2018 08:25 AM, Geert Uytterhoeven wrote:
quoted
On Wed, May 23, 2018 at 12:01 AM, Marek Vasut [off-list ref] wrote:
quoted
On 05/22/2018 04:43 PM, Geert Uytterhoeven wrote:
quoted
On Tue, May 22, 2018 at 2:02 PM, Marek Vasut [off-list ref] wrote:
quoted
Drop the MTD partitioning from DT, since it does not describe HW
and to give way to a more flexible kernel command line partition
passing.

To retain the original partitioning, assure you have enabled
CONFIG_MTD_CMDLINE_PARTS in your kernel config and add the
following to your kernel command line:

  mtdparts=spi0.0:256k at 0(loader),4096k(user),-(flash)
I think the "@0" can be dropped, as it's optional?
4m?
My take on this is that the loader is actually at offset 0x0 of the MTD
device and we explicitly state that in the mtdparts to anchor the first
partition within the MTD device and all the other partitions are at
offset +(sum of the sizes of all partitions listed before the current
one) relative to that first partition.
Where is this explicitly states for the first partition?
quoted
Removing the @0 feels fragile at best and it seems to depend on the
current behavior of the code.
Better, it also depends on the documented behavior:

Documentation/admin-guide/kernel-parameters.txt refers to
drivers/mtd/cmdlinepart.c, which states:

 * <offset>  := standard linux memsize
 *              if omitted the part will immediately follow the previous part
 *              or 0 if the first part

None of the examples listed there or under the MTD_CMDLINE_PARTS Kconfig
help text, or in a defconfig bundled with the kernel, use @0 for the first
partition.
I think this is exceptionally fragile and dangerous to depend on this,
but so be it.
Could you respin with this change?

I would also like to ask for another change, in light of recent
feedback from Olof Johansson ("Re: [GIT PULL] Renesas ARM64 Based SoC DT
Updates for v4.18").

Please consolidate the dts patches into a single patch?
I think it's better to keep them split, as each commit description mentions
what needs to be passed on the kernel command line for the corresponding
board.

Combining it in a single patch makes it much harder to extract this information.
Unless you're fine with a list:

   koelsch: ...
   wheat: mtdparts=spi0.0:256k at 0(loader),4096k(user),-(flash)
Lets try a list.
Reposted with a list, twice :/

-- 
Best regards,
Marek Vasut
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