linux-kernel - Re: [PATCH v2] soc: imx: Add generic i.MX8 SoC driver

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Message-ID: <20190227084116.42yrs26i5xlkppgl@fsr-ub1664-175>
Date:   Wed, 27 Feb 2019 08:41:17 +0000
From:   Abel Vesa <abel.vesa@....com>
To:     Leonard Crestez <leonard.crestez@....com>
CC:     "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Jacky Bai <ping.bai@....com>, dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stefan@...er.ch" <stefan@...er.ch>,
        "abelvesa@...ux.com" <abelvesa@...ux.com>,
        "spencercw@...il.com" <spencercw@...il.com>,
        Fabio Estevam <fabio.estevam@....com>,
        "robh@...nel.org" <robh@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Anson Huang <anson.huang@....com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: Re: [PATCH v2] soc: imx: Add generic i.MX8 SoC driver

On 19-02-26 13:34:52, Leonard Crestez wrote:
> On Tue, 2019-02-26 at 10:53 +0000, Abel Vesa wrote:
> > Add generic i.MX8 SoC driver along with the i.MX8MQ SoC specific code.
> > For now, only i.MX8MQ revision B1 is supported. For any other, i.MX8MQ
> > revision it will print 'unknown'.
> > 
> > +	np = of_find_compatible_node(NULL, NULL, "fsl,imx8mq-ocotp");
> > +	if (!np)
> > +		goto out;
> > +
> > +	ocotp_base = of_iomap(np, 0);
> > +	WARN_ON(!ocotp_base);
> > +
> > +	magic = readl_relaxed(ocotp_base + IMX8MQ_SW_INFO_B1);
> > +	if (magic == IMX8MQ_SW_MAGIC_B1)
> > +		rev = REV_B1;
> 
> Turns out that imx8mq version determination is uniquely messy. I think
> we should try to print the revision number even for older chips so that
> we know how old they are, but this code can be enhanced in later
> patches.
> 

Fair enough. I believe we should stick to B1 only for now though.

> In the vendor tree we handle this with a SIP call to ATF, it's not
> clear why we shouldn't just upstream that (in both ATF and Linux).
> 

Question here is: do we need to go through psci for things like revision ?
I believe the cost is not worth it.

> Also, there are some imx soc revision declarations in
> include/soc/imx/revision.h. Those are implemented in arch/arm/mach-imx
> for older chips, would it make sense for soc-imx8 to define
> imx_get_soc_revision?
> 

I'm totally against the use of imx_get_soc_revision everywhere. Plus,
according to our internal tree there doens't seem to indicate a need for
such a thing for imx8. Anyway, that can be added later on if necessary.

> --
> Regards,
> Leonard