Home
Reading
Searching
Subscribe
Sponsors
Statistics
Posting
Contact
Spam
Lists
Links
About
Hosting
Filtering
Features Download
Marketing
Archives
FAQ
Blog
 
Gmane
From: Ezequiel Garcia <ezequiel.garcia <at> free-electrons.com>
Subject: [PATCH 00/21] Armada 370/XP NAND support
Newsgroups: gmane.linux.drivers.mtd
Date: Thursday 19th September 2013 16:01:24 UTC (over 3 years ago)
Hi everyone,

As some of you know, I'm working on implementing the long-awaited NAND
support in Armada 370/XP SoCs.

The controller is the same as PXA3XX (NFCv1), plus some changes,
and therefore it's called NFCv2. As expected, it should be supported
by pxa3xx-nand, plus some changes.

First of all I'd like to introduce the controller and explain how it
expects the data, ECC and OOB layout within a page. We might add this
as documentation inside the driver or in Documentation/mtd, so feel free
to ask anything that looks suspicious or is not clear enough.

* Page layout

The controller has a 2176 bytes FIFO buffer. Therefore, in order to support
larger pages, I/O operations on 4 KiB and 8 KiB pages is done with a set of
chunked transfers.

For instance, if we choose a 2048 data chunk and BCH ECC we will have
to use this layout in the pages:

 
------------------------------------------------------------------------------
  | 2048B data | 32B spare | 30B ECC || 2048B data | 32B spare | 30B ECC |
... |
 
------------------------------------------------------------------------------

The last remaining area is unusable (i.e. wasted).

To match this, my current (already working!) implementation acts like
a layout "impedance matcher" to produce in an internal driver's buffer
this layout:

  ------------------------------------------
  |     4096B data     |     64B spare     |
  ------------------------------------------

In order to achieve reading (for instance), we issue several READ0 commands
(with some additional controller-specific magic) and read two chunks of
2080B
(2048 data + 64 spare) each.

The driver accomodates this data to expose the NAND base a contiguous 4160B
buffer
(4096 data + 64 spare).

* ECC

The controller has built-in hardware ECC capabilities. In addition it is
completely
configurable, and we can choose between Hamming and BCH ECC. If we choose
BCH ECC
then the ECC code will be calculated for each transfered chunk and expected
to be
located (when reading/programming) at specific locations.

So, repeating the above scheme, a 2048B data chunk will be followed by 32B
spare,
and then the ECC controller will read/write the ECC code (30B in this
case):

  ------------------------------------
  | 2048B data | 32B spare | 30B ECC |
  ------------------------------------

* OOB

Because of the above scheme, and because the "spare" OOB is really located
in
the middle of a page, spare OOB cannot be read or write independently of
the
data area. In other words, in order to read the OOB (aka READOOB), the
entire
page (aka READ0) has to be read.

In the same sense, in order to write to the spare OOB (aka SEQIN,
column = 4096 + PAGEPROG) the driver has to read the entire page first to
the
driver's buffer. Then it should fill the OOB, and finally program the
entire page,
data and oob included.

Notice, that while this is possible, I haven't included OOB only write
support
(i.e. OOB write without data write) in this first patchset. I'm not sure
why
would we need it, so I'd like to know others opinion on this matter.

Of course, writing to the OOB is supported, as long as this write is done
*with* data. Following the examples above, writing an entire 4096 + OOB
page
is supported.

* Clocking and timings

This first patchset adds a dummy nand-clock to the device tree just to
allow
the driver to get it. Timings configuration is overriden for now using the
'keep-config' DT parameter. The next round will likely include proper clock
support plus timings configuration.

* About this patchset

This has been tested on Armada 370 Mirabox and Armada XP GP boards.

Currently nandtest, mtd_pagetest, mtd_readtest pass while mtd_oobtest fails
(due to lack of OOB write support). This means that JFFS2 is not supported,
and UBIFS is a must.

The patches are based in l2-mtd's master branch and I've pushed a branch
to our github in case anyone wants to test this:

  https://github.com/MISL-EBU-System-SW/mainline-public/tree/pxa3xx-armada-nand-v1

The series is fairy complex and lengthy, so any feedback is more than
welcome,
as well as questions, suggestions or flames. Also, if anyone has a PXA
board
(Daniel?) to test possible regressions I would really appreciate it.

* A note about Mirabox testing

As this work is not considered completely stable, be extra careful when
trying
on the Mirabox. The Mirabox has the bootloader at NAND, and there's some
risk
to brick the board.

That said: I've been using the driver on my Mirabox all morning (with my
own
Buildroot prepared UBIFS image) and so far everything works fine.

If despite this you happen to brick the board, Willy Tarreau has provided
excellent instructions to un-brick the Mirabox:

  http://1wt.eu/articles/mirabox-vs-guruplug/

Thanks!

Ezequiel Garcia (21):
  mtd: nand: pxa3xx: Allocate data buffer on detected flash size
  mtd: nand: pxa3xx: Disable OOB on arbitrary length commands
  mtd: nand: pxa3xx: Use a completion to signal device ready
  mtd: nand: pxa3xx: Add bad block handling
  mtd: nand: pxa3xx: Add driver-specific ECC BCH support
  mtd: nand: pxa3xx: Configure detected pages-per-block
  mtd: nand: pxa3xx: Clear cmd buffer #3 (NDCB3) on command start
  mtd: nand: pxa3xx: Make config menu show supported platforms
  mtd: nand: pxa3xx: Split FIFO size from to-be-read FIFO count
  mtd: nand: pxa3xx: Replace host->page_size by mtd->writesize
  mtd: nand: pxa3xx: Add helper function to set page address
  mtd: nand: pxa3xx: Remove READ0 switch/case falltrough
  mtd: nand: pxa3xx: Split prepare_command_pool() in two stages
  mtd: nand: pxa3xx: Move the data buffer clean to
    prepare_start_command()
  mtd: nand: pxa3xx: Add a read/write buffers markers
  mtd: nand: pxa3xx: Introduce multiple page I/O support
  mtd: nand: pxa3xx: Add multiple chunk write support
  ARM: mvebu: Add a fixed 0Hz clock to represent NAND clock
  ARM: mvebu: Add support for NAND controller in Armada 370/XP
  ARM: mvebu: Enable NAND controller in Armada XP GP board
  ARM: mvebu: Enable NAND controller in Armada 370 Mirabox

 arch/arm/boot/dts/armada-370-mirabox.dts      |  21 +
 arch/arm/boot/dts/armada-370-xp.dtsi          |  19 +
 arch/arm/boot/dts/armada-xp-gp.dts            |   8 +
 drivers/mtd/nand/Kconfig                      |   4 +-
 drivers/mtd/nand/pxa3xx_nand.c                | 546
+++++++++++++++++++++-----
 include/linux/platform_data/mtd-nand-pxa3xx.h |   3 +
 6 files changed, 493 insertions(+), 108 deletions(-)

-- 
1.8.1.5


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/
 
CD: 4ms