Re: [PATCH 02/12] mtd: nand: add reworked Marvell NAND controller driver

[Miquel RAYNAL <miquel.raynal-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

On Mon, 11 Dec 2017 13:27:30 -0300
Ezequiel Garcia <ezequiel-30ULvvUtt6G51wMPkGsGjgyUoB5FGQPZ@public.gmane.org> wrote:

> On 7 December 2017 at 17:18, Miquel Raynal
> <miquel.raynal-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> wrote:
> > Add marvell_nand driver which aims at replacing the existing
> > pxa3xx_nand driver.
> >
> > The new driver intends to be easier to understand and follows the
> > brand new NAND framework rules by implementing hooks for every
> > pattern the controller might support and referencing them inside a
> > parser object that will be given to the core at each ->exec_op()
> > call.
> >
> > Raw accessors are implemented, useful to test/debug
> > memory/filesystem corruptions. Userspace binaries contained in the
> > mtd-utils package may now be used and their output trusted.
> >
> > Timings may not be kept from the bootloader anymore, the timings
> > used for instance in U-Boot were not optimal and it supposed to
> > have NAND support (and initialized) in the bootloader.
> >
> > Thanks to the improved timings, implementation of ONFI mode 5
> > support (with EDO managed by adding a delay on data sampling),
> > merging the commands together and optimizing writes in the command
> > registers, the new driver may achieve faster throughputs in both
> > directions. Measurements show an improvement of about +23% read
> > throughput and +24% write throughput. These measurements have been
> > done with an Armada-385-DB-AP (4kiB NAND pages forced in 4-bit
> > strength BCH ECC correction) using the userspace tool 'flash_speed'
> > from the MTD test suite.
> >
> > Besides these important topics, the new driver addresses several
> > unsolved known issues in the old driver which:
> > - did not work with ECC soft neither with ECC none ;
> > - relied on naked read/write (which is unchanged) while the NFCv1
> >   embedded in the pxa3xx platforms do not implement it, so several
> >   NAND commands did not actually ever work without any notice (like
> >   reading the ONFI PARAM_PAGE or SET/GET_FEATURES) ;
> > - wrote the OOB data correctly, but was not able to read it
> > correctly past the first OOB data chunk ;
> > - did not displayed ECC bytes ;
> > - used device tree bindings that did not allow more than one NAND
> > chip, and did not allow to choose the correct chip select if not
> >   incrementing from 0. Plus, the Ready/Busy line used had to be 0.
> >
> > Old device tree bindings are still supported but deprecated. A more
> > hierarchical view has to be used to keep the controller and the NAND
> > chip structures clearly separated both inside the device tree and
> > also in the driver code.
> >  
> 
> So, is this driver fully compatible with the current pxa3xx-nand
> driver?

It should be!

> 
> Have you tested with U-Boot's driver (based on the pxa3xx-nand)?
> 
> I recally some subtle issues with the fact that U-Boot and Linux had
> to agree about the BBT format.

I kept the pxa3xx_nand driver BBT format.

This is something I mistakenly omitted from the commit message:

There are 5 supported layouts in the driver (the same as withing the
pxa3xx_nand driver):
    1/ Page: 512B, strength 1b/512B (hamming)
    2/ Page: 2kiB, strength 4b/2kiB (hamming)
    3/ page: 2kiB, strength 16b/2kiB (BCH)
    4/ page: 4kiB, strength 16b/2kiB (BCH)
    5/ page: 4kiB, strength 32b/2kiB (BCH)

Layout 2 has been tested with CM_X300 compulab module (PXA SoC) with
and without DMA.
Layout 4 has been tested with an Armada 385 db, an Armada 7040 DB and
an Armada 8040 DB.
Layout 5 has been tested with an Armada 398 db.

Layout 1 has been tested with the Armada 385 db with some hacks.
Layout 3 has been tested with the Armada 385 db with some other hacks,
that is why I am concerned about the other thread on the MTD mailing
list "wait timeout when scanning for BB" where a 2kiB page with
16b/2048B strength is in use.

Regards,
Miquèl
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