linux-kernel - Re: [PATCH v7 4/5] i2c: aspeed: added driver for Aspeed I2C

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Date:   Mon, 8 May 2017 16:34:58 -0700
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     Wolfram Sang <wsa@...-dreams.de>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Joel Stanley <joel@....id.au>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Kachalov Anton <mouse@...c.ru>,
        Cédric Le Goater <clg@...d.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Ryan Chen <ryan_chen@...eedtech.com>
Subject: Re: [PATCH v7 4/5] i2c: aspeed: added driver for Aspeed I2C

Sorry for the spam everyone, email client did not do what I expected it to do.

I would like to release another version this week or next week, and I
think that we are pretty closed to having something we can apply, but
before I do that, I want to get something resolved:

> +static int __aspeed_i2c_init(struct aspeed_i2c_bus *bus,
> +                            struct platform_device *pdev)
> +{
> +       int ret;
> +
> +       /* Disable everything. */
> +       writel(0, bus->base + ASPEED_I2C_FUN_CTRL_REG);
> +
> +       ret = __aspeed_i2c_init_clk(bus, pdev);
> +       if (ret < 0)
> +               return ret;
> +
> +       /* Enable Master Mode */
> +       writel(readl(bus->base + ASPEED_I2C_FUN_CTRL_REG) |
> +              ASPEED_I2CD_MASTER_EN |
> +              /* TODO: provide device tree option for multi-master mode. */

I am curious what everyone thinks about this. It seemed that, earlier
on, people did not like me disabling multi-master mode, but I think
that it would make bus recovery not work as well. Given that, I think
it makes the most sense to provide a device tree option either to
enable multi-master support or disable it. Thoughts?

> +              ASPEED_I2CD_MULTI_MASTER_DIS,
> +              bus->base + ASPEED_I2C_FUN_CTRL_REG);
> +
> +       /* Set interrupt generation of I2C controller */
> +       writel(ASPEED_I2CD_INTR_ALL, bus->base + ASPEED_I2C_INTR_CTRL_REG);
> +
> +       return 0;
> +}