[U-Boot] [PATCH v2 14/38] spi: Add support for memory-mapped flash

[Simon Glass]

Hi Vignesh,

On Wed, 16 Oct 2019 at 04:28, Vignesh Raghavendra <vigneshr at ti.com> wrote:
>
> Hi Simon,
>
> On 12/10/19 10:03 AM, Bin Meng wrote:
> > Hi Simon,
> >
> > On Sat, Oct 12, 2019 at 11:08 AM Simon Glass <sjg at chromium.org> wrote:
> >>
> >> Hi Bin,
> >>
> >> On Wed, 9 Oct 2019 at 07:55, Bin Meng <bmeng.cn at gmail.com> wrote:
> >>>
> >>> Hi Simon,
> >>>
> >>> On Wed, Sep 25, 2019 at 10:12 PM Simon Glass <sjg at chromium.org> wrote:
> >>>>
> >>>> On x86 platforms the SPI flash can be mapped into memory so that the
> >>>> contents can be read with normal memory accesses.
> >>>>
> >>>> Add a new SPI flash method to find the location of the SPI flash in
> >>>> memory. This differs from the existing device-tree "memory-map" mechanism
> >>>> in that the location can be discovered at run-time.
> >>>>
>
> Whats is the usecase? Why can't spi_flash_read() be used instead?
> Flash + Controller driver can underneath take care of using memory
> mapped mode to read data from flash right while making sure that access
> is within valid window?

I can see spi_flash_read_dm() but it does not support returning a
pointer to the data, only reading it.

Also I cannot find any documentation about any of this. I've been
looking in the doc/ directory.

I found the spi_mem.h file but it doesn't mention the meaning of the
in and out buffer pointers so I don't know how to use them.

Is there an API missing or just comments/documentation?

Regards,
Simon