linux-kernel - UBIFS LEB properties tree with odd addresses

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Date:   Tue, 25 Oct 2016 06:05:32 +0000
From:   Naga Sureshkumar Relli <naga.sureshkumar.relli@...inx.com>
To:     Christoph Hellwig <hch@...radead.org>,
        Richard Weinberger <richard@....at>
CC:     "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "dedekind1@...il.com" <dedekind1@...il.com>,
        "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "Punnaiah Choudary Kalluri" <punnaia@...inx.com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>
Subject: UBIFS LEB properties tree with odd addresses

Hi,

We are testing UBIFS (NOR) on Zynq Ultrascale+ MPSoC GQSPI controller driver.
Apart from my previous mail thread about UBIFS, i.e along with dma issue I am facing one more
Problem related to offsets.

Info about GQSPI Controller:
This controller can access the flash device in the following modes.
1. Single flash mode
2. Two spi flash memories with separate buses (dual parallel)

Single flash mode: it is normal configuration, one controller and one flash memory

In dual parallel mode following are the functionalities:
1) Supporting two SPI flash memories operating in parallel. 8 I/O lines.
2) Chip selects and clock are shared to both the flash devices
3) This mode is targeted for faster read/write speed and also doubles the size
4) Commands/data can be transmitted/received from both the devices(mirror), or only upper or only lower flash memory devices.
5) Data arrangement:
    With stripe (controller configuration) enabled,
    Even bytes i.e. 0, 2, 4,... are transmitted on Lower Data Bus
    Odd bytes i.e. 1, 3, 5,.. are transmitted on Upper Data Bus.

Kernel version : 4.4.0
Controller limitation: ZynqMP gqspi controller supports only even addresses when two flash devices are connected (dual parallel mode).

Issue I am facing:
-> Since our controller supports even addresses in dual parallel mode
We are seeing issues with ubifs in dual parallel mode and jffs2 is working fine and we observed the following:

IN dual parallel mode, the Erase block size was 128KiB whereas single flash mode the Erase block size was 64KiB.
In single flash mode, we are getting pnode_sz value as 16 and for dual parallel mode we are getting an odd value 17
And ltab_sz value in single mode as 12 and in dual parallel mode as 11.
Because of these odd values, check_lpt_type  offset argument is odd address and hence lpt_type error.

When I ran the mnt command, I am getting the following error
"UBIFS error (ubi0:0 pid 1882): check_lpt_type: invalid type (4) in LPT node type 2"
Ran the below commands:
a)ubiformat /dev/mtd0 -e 0 -y
b)ubiattach -p /dev/mtd0
c)ubimkvol -N data -m /dev/ubi0
d)mount -t ubifs ubi0:data /mnt

So for temporary hack we did the following change
In fs/ubifs/lpt.c
In do_calc_lpt_geom(), added the following
+       if (c->pnode_sz % 2)
+               c->pnode_sz += 1; 
+       if (c->ltab_sz % 2)
+               c->ltab_sz += 1;

Please kindly suggest, I need your inputs, changing the pnode_sz and ltab_sz to even in lpt.c, will it impact on any others?
We can do the same change in spi layer (change the address to even) but the above properties won't reflect in ubi layer.
Kindly please suggest.
If I haven't provided sufficient information, please let me know.

Thanks,
Naga Sureshkumar Relli