[PATCH v2 00/27] Armada 370/XP NAND support
Ezequiel Garcia
ezequiel.garcia at free-electrons.com
Thu Oct 31 08:58:09 PDT 2013
Brian,
Can we start discussing this patchset?
I realize is a big series, but better starting sooner than later! :)
In particular... (see below)
On Fri, Oct 18, 2013 at 08:02:27PM -0300, Ezequiel Garcia wrote:
> Hi guys,
>
> This is the v2 of the work implementing NAND support in Armada 370/XP SoCs.
> This series is probably not yet complete (see below), but I feel like
> we're really closer now :-)
>
> As in the previous version and given I don't have any public datasheet
> to show, I'll try to write some of the most relevant parts of the controller.
>
> * NFCv2 controller background
>
> 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 set "BCH" ECC (see below)
> we'll have this layout in the pages:
>
> ------------------------------------------------------------------------------
> | 2048B data | 32B spare | 30B ECC || 2048B data | 32B spare | 30B ECC | ... |
> ------------------------------------------------------------------------------
>
> The driver reads the data and spare portions independently and builds an internal
> buffer with this layout (in the 4 KiB page case):
>
> ------------------------------------------
> | 4096B data | 64B spare |
> ------------------------------------------
>
> Also, for the READOOB command the driver disables the ECC and reads a 'spare + ECC'
> OOB, one per chunk read.
>
> -------------------------------------------------------------------
> | 4096B data | 32B spare | 30B ECC | 32B spare | 30B ECC |
> -------------------------------------------------------------------
>
> So, 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 + 32 spare) each.
> The driver accomodates this data to expose the NAND core a contiguous buffer
> (4096 data + spare) or (4096 + spare + ECC + spare + ECC).
>
> * ECC
>
> The controller has built-in hardware ECC capabilities. In addition it is
> configurable between two modes: 1) Hamming, 2) BCH.
>
> Note that the actual BCH mode: BCH-4 or BCH-8 will depend on the way
> the controller is configured to transfer the data.
>
> In the BCH mode the ECC code will be calculated for each transfered chunk
> and expected to be located (when reading/programming) right after the spare
> bytes as the figure above shows.
>
> 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 |
> ------------------------------------
>
> If the ECC mode is 'BCH' then the ECC is *always* 30 bytes long.
> If the ECC mode is 'Hamming' the ECC is 6 bytes long, for each 512B block.
> So in Hamming mode, a 2048B page will have a 24B ECC.
>
> Despite all of the above, the controller requires the driver to only read or
> write in multiples of 8-bytes, because the data buffer is 64-bits.
>
> * Changes from v1
>
> Aside from several changes based in Brian's feedback, the main changes
> from v1 are:
>
> * The controller's clock source is now fully modeled, see patche 1 to 4.
> Of course, none of those patches should be taken through the mtd
> subsystem, but I'm adding them here for completeness.
>
> * The chip's cmdfunc() is now independently implemented in each SoC variant.
> The rationale behind this decision is that 'chunked' I/O is the only tested
> mode on the Armada370 variant, while the old 'vanilla' I/O is the only
> tested mode on the PXA variant.
>
> So it's safer to have an implementation for each variant.
>
> * Added support for BCH-8, in other words: 8-bits of correction in a 512-byte
> region. This is obtained by using a data chunk size of 1024B, thus doubling
> the ECC BCH strength, as per this ECC engine mechanism.
>
> * The ECC layout in use, which must be set according to the page size and
> desired ECC strength is now strictly chosen to match only the tested
> combinations.
>
> * Pending stuff
>
> 1. Factory bad blocks handling
>
> Currently, there's no factory bad block initial scan (when the bad block
> table is missing). The ECC BCH requires to layout the device's pages in
> a splitted "data + OOB + data + OOB" way. This layout being different from
> the factory layout. In other words,
>
> Factory view:
>
> -----------------------------------------------
> | Data |x OOB |
> -----------------------------------------------
>
> Driver's view:
>
> -----------------------------------------------
> | Data | OOB | Data x | OOB |
> -----------------------------------------------
>
> It can be seen from the above, that the factory bad block marker must be
> searched within the 'data' region, and not in the usual OOB region.
>
> This seems to be similar to the gpmi-nand driver, yet I really find its
> 'bad block swapping' solution odd, so I'm trying to find something
> cleaner.
>
> 2. ECC modeling
>
> Although I've exposed some ECC information in the ECC layout, I'm still
> not sure why is this needed, or if it's needed at all.
>
> * About this patchset
>
> This is based in l2-mtd's master branch and I've pushed a branch to our
> github in case anyone wants to test it:
>
> https://github.com/MISL-EBU-System-SW/mainline-public/tree/l2-mtd/upstream-nand-v2
>
> Just as the previous, this series is complex and lengthy and any feedback will
> be highly appreciated as well as questions, suggestions or flames. Also, I hope
> our brave PXA regression tester Daniel Mack finds some time to give it a ride
> and report any issues. Daniel: I think owe you several beers already.
>
> * 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 for several days doing
> simple long-run NAND activity and everything worked 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 (27):
> clk: mvebu: Add Core Divider clock
> ARM: mvebu: Add Core Divider clock device-tree binding
> ARM: mvebu: Add a 2 GHz fixed-clock Armada 370/XP
> ARM: mvebu: Add the core-divider clock to Armada 370/XP
> mtd: nand: pxa3xx: Make config menu show supported platforms
> mtd: nand: pxa3xx: Prevent sub-page writes
> mtd: nand: pxa3xx: Early variant detection
> mtd: nand: pxa3xx: Use chip->cmdfunc instead of the internal
> 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: 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
^^
This one and ...
> mtd: nand: pxa3xx: Clear cmd buffer #3 (NDCB3) on command start
> 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: Fix SEQIN column address set
> mtd: nand: pxa3xx: Add a read/write buffers markers
> mtd: nand: pxa3xx: Introduce multiple page I/O support
^^^
.. this one seems to me like the most conflicting patches as
they extend the ECC, adding BCH. Could you review them and
provide any comments?
> mtd: nand: pxa3xx: Add multiple chunk write support
> mtd: nand: pxa3xx: Add ECC BCH correctable errors detection
> 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
>
> .../bindings/clock/mvebu-corediv-clock.txt | 19 +
> arch/arm/boot/dts/armada-370-mirabox.dts | 21 +
> arch/arm/boot/dts/armada-370-xp.dtsi | 26 +
> arch/arm/boot/dts/armada-xp-gp.dts | 8 +
> drivers/clk/mvebu/Kconfig | 5 +
> drivers/clk/mvebu/Makefile | 1 +
> drivers/clk/mvebu/clk-corediv.c | 223 +++++++
> drivers/mtd/nand/Kconfig | 4 +-
> drivers/mtd/nand/pxa3xx_nand.c | 686 ++++++++++++++++-----
> include/linux/platform_data/mtd-nand-pxa3xx.h | 3 +
> 10 files changed, 856 insertions(+), 140 deletions(-)
> create mode 100644 Documentation/devicetree/bindings/clock/mvebu-corediv-clock.txt
> create mode 100644 drivers/clk/mvebu/clk-corediv.c
>
> --
> 1.8.1.5
>
Huang: It seems gpmi-nand driver has some similar quirks,
so I'd like if you could take some time to review my patches.
I realise that you might be busy with your own patches, but the
best way of having them cross-reviewed is by doing some review
on others work.
Thanks!
--
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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