linux-kernel - Re: [PATCH 1/2][v3] i2c: qup: add ACPI support

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Date:	Sun, 5 Jun 2016 13:57:50 -0500
From:	Andy Gross <andy.gross@...aro.org>
To:	Austin Christ <austinwc@...eaurora.org>
Cc:	wsa@...-dreams.de, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	nkaje@...eaurora.org, rruigrok@...eaurora.org,
	timur@...eaurora.org, cov@...eaurora.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2][v3] i2c: qup: add ACPI support

On Thu, May 26, 2016 at 01:37:56PM -0600, Austin Christ wrote:

<snip>

> @@ -1354,14 +1359,13 @@ static void qup_i2c_disable_clocks(struct qup_i2c_dev *qup)
>  static int qup_i2c_probe(struct platform_device *pdev)
>  {
>  	static const int blk_sizes[] = {4, 16, 32};
> -	struct device_node *node = pdev->dev.of_node;
>  	struct qup_i2c_dev *qup;
>  	unsigned long one_bit_t;
>  	struct resource *res;
>  	u32 io_mode, hw_ver, size;
>  	int ret, fs_div, hs_div;
> -	int src_clk_freq;
> -	u32 clk_freq = 100000;
> +	u32 src_clk_freq = 0;
> +	u32 clk_freq = 0;
>  	int blocks;
>  
>  	qup = devm_kzalloc(&pdev->dev, sizeof(*qup), GFP_KERNEL);
> @@ -1372,7 +1376,12 @@ static int qup_i2c_probe(struct platform_device *pdev)
>  	init_completion(&qup->xfer);
>  	platform_set_drvdata(pdev, qup);
>  
> -	of_property_read_u32(node, "clock-frequency", &clk_freq);
> +	ret = device_property_read_u32(qup->dev, "clock-frequency", &clk_freq);

Why do we need a warning if the clock-frequency is not specified?  It is
optional in the DT documentation, is it not in the ACPI?

> +	if (ret) {
> +		dev_warn(qup->dev, "using default clock-frequency %d",
> +			DEFAULT_CLK_FREQ);
> +		clk_freq = DEFAULT_CLK_FREQ;

You could just assign the DEFAULT_CLK_FREQ in the variable declaration instead
of 0.  read_property does not modify the variable unless it finds it or does the
ACPI version modify if not found?

> +	}
>  
>  	if (of_device_is_compatible(pdev->dev.of_node, "qcom,i2c-qup-v1.1.1")) {
>  		qup->adap.algo = &qup_i2c_algo;
> @@ -1454,20 +1463,31 @@ nodma:
>  		return qup->irq;
>  	}
>  

<snip>

Regards,

Andy