Re: [PATCH v2 3/6] mtd: rawnand: add NVIDIA Tegra NAND Flash controller driver

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Stefan,

On Thu, 31 May 2018 11:37:41 +0200, Stefan Agner <stefan@agner.ch>
wrote:

> On 27.05.2018 23:54, Stefan Agner wrote:
> > Add support for the NAND flash controller found on NVIDIA
> > Tegra 2 SoCs. This implementation does not make use of the
> > command queue feature. Regular operations/data transfers are
> > done in PIO mode. Page read/writes with hardware ECC make
> > use of the DMA for data transfer.
> > 
> > Signed-off-by: Lucas Stach <dev@lynxeye.de>
> > Signed-off-by: Stefan Agner <stefan@agner.ch>
> > ---
> >  MAINTAINERS                       |   7 +
> >  drivers/mtd/nand/raw/Kconfig      |   6 +
> >  drivers/mtd/nand/raw/Makefile     |   1 +
> >  drivers/mtd/nand/raw/tegra_nand.c | 999 ++++++++++++++++++++++++++++++
> >  4 files changed, 1013 insertions(+)
> >  create mode 100644 drivers/mtd/nand/raw/tegra_nand.c
> >   
> [...]
> > +
> > +	chip->ecc.read_page = tegra_nand_read_page_hwecc;
> > +	chip->ecc.write_page = tegra_nand_write_page_hwecc;
> > +	/* Not functional for unknown reason...
> > +	chip->ecc.read_page_raw = tegra_nand_read_page;
> > +	chip->ecc.write_page_raw = tegra_nand_write_page;
> > +	*/  
> 
> I am giving up on these raw read/write_page functions. Using DMA without
> HW ECC just seems not to work.

[...]

> Note that the default implementations nand_(read|write)_page_raw which
> use exec_op do work fine! Unfortunately, the PIO mode only allows 4
> bytes in a read cycle, hence raw read/write is slow...
> 

Well, if raw accessors work in PIO mode, I suppose it's not a big deal.

Thanks for trying anyway!
Miquèl