linux-kernel - Re: [PATCH v3 3/3] i2c-ocores: sifive: add polling mode workaround for FU540-C000 SoC

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Date:   Thu, 16 May 2019 18:24:32 +0530
From:   Sagar Kadam <sagar.kadam@...ive.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     robh+dt@...nel.org, mark.rutland@....com, peter@...sgaard.com,
        Palmer Dabbelt <palmer@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] i2c-ocores: sifive: add polling mode workaround
 for FU540-C000 SoC

Hello Andrew,

On Thu, May 16, 2019 at 6:01 PM Andrew Lunn <andrew@...n.ch> wrote:
>
> > @@ -682,13 +693,24 @@ static int ocores_i2c_probe(struct platform_device *pdev)
> >
> >       irq = platform_get_irq(pdev, 0);
> >       if (irq == -ENXIO) {
> > -             i2c->flags |= OCORES_FLAG_POLL;
> > +             /*
> > +              * Set a OCORES_FLAG_BROKEN_IRQ to enable workaround for
> > +              * FU540-C000 SoC in polling mode interface of i2c-ocore driver.
> > +              * Else enable default polling mode interface for SIFIVE/OCORE
> > +              * device types.
> > +              */
> > +             match = of_match_node(ocores_i2c_match, pdev->dev.of_node);
> > +             if (match && (long)match->data ==
> > +                             (TYPE_SIFIVE_REV0 | OCORES_FLAG_BROKEN_IRQ))
>
> This looks wrong. You added:
>
> +       {
> +               .compatible = "sifive,fu540-c000-i2c",
> +               .data = (void *)TYPE_SIFIVE_REV0,
> +       },
> +       {
> +               .compatible = "sifive,i2c0",
> +               .data = (void *)TYPE_SIFIVE_REV0,
> +       },
>
> So match->data just has TYPE_SIFIVE_REV0.
I updated the device_id table into two logically separated patches as follows:-

1. Update device id table for Sifive devices
    [PATCH v3 2/3] i2c-ocore:
                  .data for sifive,fu540-540-c000 and sifive,i2c0 both
are for sifive devices hence TYPE_SIFIVE_REV0
2. Add polling mode workaround fix for fu540-c000 SoC
    [PATCH v3 3/3] i2c-ocores:
                  .data for sifive,fu540-540-c000 is of
TYPE_SIFIVE_REV0 and has a broken IRQ so the flag
OCORES_FLAG_BROKEN_IRQ is OR'd to data into device id table.

Please let me know if you feel patch 2 and patch 3 need to be squashed
together into a single patch.

>
> > +                     i2c->flags |= OCORES_FLAG_BROKEN_IRQ;
> > +             else
> > +                     i2c->flags |= OCORES_FLAG_POLL;
>
> These two don't need to be exclusive. It makes more sense to say
> SIFIVE needs to poll and it its IRQ is broken. A lot of your other
> changes then go away.
>
Other SiFive chip's with Ocore based I2C re-implementation might not
need the broken IRQ workaround.
and can use the the existing mainline polling mode interface, using
OCORES_FLAG_POLL.

Thanks & BR,
Sagar Kadam
>        Andrew