linux-kernel - Re: [RFC PATCH 1/4] EDAC: mvebu: Add driver for Marvell Armada SoCs

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Date:   Thu, 22 Jun 2017 16:11:35 +0200
From:   Jan Lübbe <jlu@...gutronix.de>
To:     Chris Packham <chris.packham@...iedtelesis.co.nz>
Cc:     bp@...en8.de, linux-arm-kernel@...ts.infradead.org,
        linux-edac@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/4] EDAC: mvebu: Add driver for Marvell Armada SoCs

Hi Chris,

On Fr, 2017-06-09 at 15:14 +0200, Jan Lübbe wrote:
> > +static void mvebu_init_csrows(struct mem_ctl_info *mci,
> > +                             struct mvebu_mc_pdata *pdata)
> [...]
> > +     devtype = (ctl >> 20) & 0x3;
> > +     switch (devtype) {
> > +     case 0x0:
> > +             dimm->dtype = DEV_X32;
> > +             break;
> > +     case 0x2:               /* could be X8 too, but no way to tell
> */
> > +             dimm->dtype = DEV_X16;
> > +             break;
> > +     case 0x3:
> > +             dimm->dtype = DEV_X4;
> > +             break;
> > +     default:
> > +             dimm->dtype = DEV_UNKNOWN;
> > +             break;
> > +     }
> This register is documented as reserved? I pulled the X8/X16
> information from the Address Control Register (CSnStruct bits).

Do you have more information on how to decode the Bus width?

It's not clear from the MV78230/78x60 docs:
- The SDRAM Configuration Register, offset 15 bit is:
  0 = Half (32 bit data bus)
  1 = Full (64 bit data bus)
- The SDRAM Address Control Register, offsets 0-1, 4-5, 8-9 and 12-13
(for CS 0, 1, 3 and 4):
  0 = X8
  1 = X16
  2 and 3 are not documented

Is this clearer in your documentation, so that we can have the same code
handle both variants? Otherwise, we'd probably need separate DT
compatibles.

Regards,
Jan
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