linux-kernel - Re: [PATCH v2 01/13] gpio: Add Elba SoC gpio driver for spi cs control

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Message-ID: <CAK9rFnxKHmzoZhbc-FK_BML-2rCY64x4REhkdZE+TWYm+VWHFg@mail.gmail.com>
Date:   Sun, 22 Aug 2021 18:24:35 -0700
From:   Brad Larson <brad@...sando.io>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Mark Brown <broonie@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Olof Johansson <olof@...om.net>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 01/13] gpio: Add Elba SoC gpio driver for spi cs control

Hi Sergey,

On Wed, Mar 31, 2021 at 11:10 AM Serge Semin <fancer.lancer@...il.com> wrote:
>
> On Sun, Mar 28, 2021 at 06:59:26PM -0700, Brad Larson wrote:
> > This GPIO driver is for the Pensando Elba SoC which
> > provides control of four chip selects on two SPI busses.
[...]
> > +static int elba_spics_probe(struct platform_device *pdev)
> > +{
> > +     struct elba_spics_priv *p;
> > +     struct resource *res;
> > +     int ret = 0;
> > +
> > +     p = devm_kzalloc(&pdev->dev, sizeof(*p), GFP_KERNEL);
> > +     if (!p)
> > +             return -ENOMEM;
> > +
>
> > +     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +     p->base = devm_ioremap_resource(&pdev->dev, res);
>
> In accordance with the DTS-node this is just a single register
> 0x307c2468-0x307c24C picked from some bigger block, which most likely
> belongs to something like a system controller. PCIe node has got
> another register from there "0x307c2480-0x307c2484/* MS CFG_WDT */",
> and some BSM device too "0x307c2080-0x307c2084". Please consider using
> syscon instead of directly requesting the resource here.
>
> -Sergey

I've looked into a few syscon based implementations which resulted in
a regressions to include Elba spi probe failure and host machine check
trying to perform PCIe access to Elba SoC.  I like the idea of
refactoring to use syscon but I don't have a functional solution to do
so.

Regards,
Brad