linux-kernel - Re: [PATCH v2 2/2] i2c: sunxi: add P2WI (Push/Pull 2 Wire Interface) controller support

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Date:	Fri, 09 May 2014 16:50:02 +0200
From:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
CC:	Wolfram Sang <wsa@...-dreams.de>,
	Randy Dunlap <rdunlap@...radead.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Shuge <shuge@...winnertech.com>, kevin@...winnertech.com,
	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] i2c: sunxi: add P2WI (Push/Pull 2 Wire Interface)
 controller support


On 09/05/2014 16:31, Maxime Ripard wrote:
> Hi Boris,
>
> On Wed, May 07, 2014 at 07:58:35PM +0200, Boris BREZILLON wrote:
>
[...]
> +
> +	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	p2wi->regs = devm_ioremap_resource(dev, r);
> +	if (IS_ERR(p2wi->regs)) {
> +		dev_err(dev, "failed to retrieve iomem resource\n");
> +		return PTR_ERR(p2wi->regs);
> You seem to be returning the error code in the next error messages. It
> would probably be a good idea to put it there too.

Yes, I'll print the err code in the error message.

>
>> +	}
>> +
>> +	snprintf(p2wi->adapter.name, sizeof(p2wi->adapter.name), pdev->name);
>> +	ret = platform_get_irq(pdev, 0);
>> +	if (ret < 0) {
>> +		dev_err(dev, "failed to retrieve irq: %d\n", ret);
>> +		return ret;
>> +	}
>> +	p2wi->irq = ret;
>> +
>> +	p2wi->clk = devm_clk_get(dev, NULL);
>> +	if (IS_ERR(p2wi->clk)) {
>> +		ret = PTR_ERR(p2wi->clk);
>> +		dev_err(dev, "failed to retrieve clk: %d\n",
>> +			ret);
>> +		return ret;
>> +	}
>> +
>> +	ret = clk_prepare_enable(p2wi->clk);
>> +	if (ret) {
>> +		dev_err(dev, "failed to enable clk: %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	parent_clk_freq = clk_get_rate(p2wi->clk);
>> +
>> +	p2wi->rstc = devm_reset_control_get(dev, NULL);
>> +	if (IS_ERR(p2wi->rstc)) {
>> +		ret = PTR_ERR(p2wi->rstc);
>> +		dev_err(dev, "failed to retrieve reset controller: %d\n",
>> +			ret);
>> +		goto err_clk_disable;
>> +	}
>> +
>> +	ret = reset_control_deassert(p2wi->rstc);
>> +	if (ret) {
>> +		dev_err(dev, "failed to deassert reset line: %d\n",
>> +			ret);
>> +		goto err_clk_disable;
>> +	}
>> +
>> +	init_completion(&p2wi->complete);
>> +	p2wi->adapter.dev.parent = dev;
>> +	p2wi->adapter.algo = &p2wi_algo;
>> +	p2wi->adapter.owner = THIS_MODULE;
>> +	p2wi->adapter.dev.of_node = pdev->dev.of_node;
>> +	platform_set_drvdata(pdev, p2wi);
>> +	i2c_set_adapdata(&p2wi->adapter, p2wi);
>> +
>> +	ret = devm_request_irq(dev, p2wi->irq, p2wi_interrupt, 0, pdev->name,
>> +			       p2wi);
>> +	if (ret) {
>> +		dev_err(dev, "can't register interrupt handler irq%d: %d\n",
>> +			p2wi->irq, ret);
>> +		goto err_reset_assert;
>> +	}
>> +
>> +	writel(P2WI_CTRL_SOFT_RST, p2wi->regs + P2WI_CTRL);
>> +
>> +	clk_div = parent_clk_freq / clk_freq;
>> +	if (!clk_div) {
>> +		dev_warn(dev,
>> +			 "clock-frequency is too high, setting it to %lu Hz\n",
>> +			 parent_clk_freq);
>> +		clk_div = 1;
>> +	} else if (clk_div > P2WI_CCR_MAX_CLK_DIV) {
>> +		dev_warn(dev,
>> +			 "clock-frequency is too low, setting it to %lu Hz\n",
>> +			 parent_clk_freq / P2WI_CCR_MAX_CLK_DIV);
>> +		clk_div = P2WI_CCR_MAX_CLK_DIV;
>> +	}
>> +
>> +	writel(P2WI_CCR_SDA_OUT_DELAY(1) | P2WI_CCR_CLK_DIV(clk_div),
>> +	       p2wi->regs + P2WI_CCR);
>> +
>> +	if (p2wi_mode_reg >= 0 && p2wi_mode_val >= 0) {
>> +		writel(P2WI_PMCR_PMU_INIT_SEND |
>> +		       P2WI_PMCR_PMU_MODE_REG(p2wi_mode_reg) |
>> +		       P2WI_PMCR_PMU_INIT_DATA(p2wi_mode_val) |
>> +		       P2WI_PMCR_PMU_DEV_ADDR(p2wi->slave_addr),
>> +		       p2wi->regs + P2WI_PMCR);
>> +
>> +		while (readl(p2wi->regs + P2WI_PMCR) &
>> +		       P2WI_PMCR_PMU_INIT_SEND)
>> +			cpu_relax();
>> +	}
> Did we actually encounter such a case? From what I've seen so far,
> both community's u-boot and Allwinner's bootloader already do this.
>
> As you know, I'm really not fond of putting random values and
> registers offsets into the DT itself. Making the assumption that the
> PMIC is already switched to P2WI by the bootloader seems pretty safe
> to me.

Hans, any opinion ?

If everybody agrees on that point, I'll remove the initialization part
from the probe (and drop the allwinner,reg-xx properties retrieval).

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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