Re: [RFC PATCH 2/3] RISC-V: Initial DTS for Microchip ICICLE board

[Ben Dooks]

On 03/11/2020 18:36, Atish Patra wrote:
> On Tue, Nov 3, 2020 at 10:28 AM Ben Dooks <ben.dooks@xxxxxxxxxxxxxxx> wrote:
> > On 03/11/2020 18:10, Cyril.Jean@xxxxxxxxxxxxx wrote:
> > > On 11/3/20 3:07 PM, Atish Patra wrote:
> > > > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > > >
> > > > On Fri, Oct 30, 2020 at 2:20 PM Ben Dooks <ben.dooks@xxxxxxxxxxxxxxx> wrote:
> >
> > ,snip[
> >
> > > > > > @Cyril : Can we enable both eMMC & sdcard at the same time ?
> > > > > I would put /both/ in but only enable the one in use for the moment.
> > > > > Our boards are booting of eMMC as supplied, so this isn't going to work
> > > > > as well. The eMMC is 8bit wide, and thus is only delivering 11MB/sec
> > > > > instead of 22MB/sec. This performance is still not great, but losing
> > > > > half the data-rate is just not good.
> > > > I am not sure what should be enabled by default. Updating sdcard is much
> > > > easier than eMMC card and we use that approach.
> > > >
> > > > @Cyril: Is there a way that we can enable both ?
> > > Yes, we can enable both but this requires a modification to the FPGA
> > > design. One of the guys prototyped this while I was away. We will move
> > > this along. This will require reprogramming the FPGA with a new design
> > > and HSS version.
> > >
> > > Regards,
> > >
> > > Cyril.
> >
> > I either missed or couldn't find a way of forcing the boot mode to be
> > from the SD slot. Have I missed something? At the moment we'd like to
> > have more storage available as the ~7G free on the eMMC is not enough.
>
> I use tftpboot to load the kernel & DT from the network. SD card is
> enabled in this DT and Linux
> kernel uses SD slot instead of eMMC.
>
> To summarize, eMMC is used for HSS & U-Boot while SD card is used for
> Linux which makes
> more storage available to Linux.
>
> IMO, we should enable the sdcard for Linux DT until updated FPGA
> design & HSS is available.

Interesting as for me the default is for Linux to use the eMMC as
well. I can't see any way for forcing the selection lines in the
DT to say eMMC vs SD.

If there is a way of controlling the selection lines then it might
be possible to have both cards enabled with a bus selection MUX in
software.


--
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius

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