linux-kernel - Re: [PATCH v9 8/8] EDAC: armada

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Message-ID: <1564347129.9737.19.camel@alliedtelesis.co.nz>
Date:   Sun, 28 Jul 2019 20:52:09 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     "james.morse@....com" <james.morse@....com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "jlu@...gutronix.de" <jlu@...gutronix.de>,
        "bp@...en8.de" <bp@...en8.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "patches@...linux.org.uk" <patches@...linux.org.uk>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>
Subject: Re: [PATCH v9 8/8] EDAC: armada_xp: Add support for more SoCs

On Fri, 2019-07-26 at 15:51 +0100, James Morse wrote:
> Hi Chris,
> 
> On 12/07/2019 04:49, Chris Packham wrote:
> > 
> > The Armada 38x and other integrated SoCs use a reduced pin count so
> > the
> > width of the SDRAM interface is smaller than the Armada XP SoCs.
> > This
> > means that the definition of "full" and "half" width is reduced
> > from
> > 64/32 to 32/16.
> > 
> > diff --git a/drivers/edac/armada_xp_edac.c
> > b/drivers/edac/armada_xp_edac.c
> > index 3759a4fbbdee..7f227bdcbc84 100644
> > --- a/drivers/edac/armada_xp_edac.c
> > +++ b/drivers/edac/armada_xp_edac.c
> > @@ -332,6 +332,11 @@ static int axp_mc_probe(struct platform_device
> > *pdev)
> >  
> >  	axp_mc_read_config(mci);
> >  
> > +	/* These SoCs have a reduced width bus */
> > +	if (of_machine_is_compatible("marvell,armada380") ||
> > +	    of_machine_is_compatible("marvell,armadaxp-98dx3236"))
> > +		drvdata->width /= 2;
> So the hardware's SDRAM_CONFIG_BUS_WIDTH value is wrong? Yuck.
> 

The maximum width differs between Armada-XP (64-bit) and Armada-38x
(32-bit). There is still strapping to control half-width vs full-width.

> Is it too late for the DTs on these two systems to provide a DT
> version of the 'bus_width'
> to override the hardware's mis-advertised value?

In an earlier iteration I did have a DT property as you suggest. The
problem is that something like "bus-width = <32>" is ambiguous. On
Armada-XP this means the strapping is for half-width but on Armada-38x
you'd need to strap to full-width. That's why we settled on the mode
interpreting the strapping against SoC[1].

[1] https://lore.kernel.org/linux-arm-kernel/1502444067.1333.7.camel@pe
ngutronix.de/

> 
> This way you don't need to grow this list.
> 
> Acked-by: James Morse <james.morse@....com>
> 
> 
> Thanks,
> 
> James