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

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Mon, 11 Dec 2017 17:55:06 +0100
Miquel RAYNAL <miquel.raynal@free-electrons.com> wrote:

> On Mon, 11 Dec 2017 13:27:30 -0300
> Ezequiel Garcia <ezequiel@vanguardiasur.com.ar> wrote:
> 
> > On 7 December 2017 at 17:18, Miquel Raynal
> > <miquel.raynal@free-electrons.com> 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)

Are you sure of #5? I thought the engine was only capable of modifying
the ECC block size, not the strength. If this is the case, then mode #5
is actually 16b/1024kiB.

> 
> 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