[U-Boot] [PATCH v2 2/2] mtd: add altera quadspi driver

Marek Vasut
2015-11-05T15:51:55Z

On Thursday, November 05, 2015 at 03:57:01 PM, Jagan Teki wrote:
> Hi Thomas,
>
> On 5 November 2015 at 20:15, Thomas Chou <thomas@wytron.com.tw> wrote:
> > Hi Jagan,
> >
> > On 2015?11?05? 22:25, Jagan Teki wrote:
> >> On 5 November 2015 at 14:17, Thomas Chou <thomas@wytron.com.tw> wrote:
> >>> Add Altera Generic Quad SPI Controller support. The controller
> >>> converts SPI NOR flash to parallel flash interface. So it is
> >>> not like other SPI flash, but rather like CFI flash.
> >>
> >> Can you wait till spi-nor ready? it doesn't make sense to have Serial
> >> NOR to created as parallel NOR.
> >
> > The altera quad spi core is very special that the hardware handle the
> > spi-nor protocol. The core is designed to replace the CFI flash
> > interface. So there is nothing to do with SPI from the parallel flash
> > interface. It is memory mapped. There is no SPI interface. There is
> > nothing related to SPI programming. So please don't worry about the
> > progress on spi-nor. The core should belong to parallel flash, but not
> > serial flash.
>
> Agreed that this is not doing any generic spi things, but it's a
> spi-nor controller all spi-nor controller should be part of spi-nor
> subsystem Linux agreed and have a framework for that.

The underlying technology is not exposed to the programmer, so this argument
is moot. The behavior of this device is closer to CFI flash.

> drivers/mtd/spi-nor/fsl-quadspi.c
> drivers/mtd/spi-nor/nxp-spifi.c
>
> all these are spi-nor controller which doesn't do any generic spi
> things but should be in spi-nor subsystem. Even Marek send altera_qspi
> as spi-nor controller [1]

This is because that thing communicates like a SPI controller.

> Since I'm working on similar spi-nor subsystem what Linux have +
> driver model little worried about this because once we have spi-nor
> again it should be a re-work.

Your work and this driver are orthogonal things.

> [1] http://lists.infradead.org/pipermail/linux-mtd/2015-April/058650.html

Best regards,
Marek Vasut