drivers/cpufreq/davinci-cpufreq.c

Source file repositories/reference/linux-study-clean/drivers/cpufreq/davinci-cpufreq.c

File Facts

System
Linux kernel
Corpus path
drivers/cpufreq/davinci-cpufreq.c
Extension
.c
Size
3833 bytes
Lines
156
Domain
Driver Families
Bucket
drivers/cpufreq
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct davinci_cpufreq {
	struct device *dev;
	struct clk *armclk;
	struct clk *asyncclk;
	unsigned long asyncrate;
};
static struct davinci_cpufreq cpufreq;

static int davinci_target(struct cpufreq_policy *policy, unsigned int idx)
{
	struct davinci_cpufreq_config *pdata = cpufreq.dev->platform_data;
	struct clk *armclk = cpufreq.armclk;
	unsigned int old_freq, new_freq;
	int ret = 0;

	old_freq = policy->cur;
	new_freq = pdata->freq_table[idx].frequency;

	/* if moving to higher frequency, up the voltage beforehand */
	if (pdata->set_voltage && new_freq > old_freq) {
		ret = pdata->set_voltage(idx);
		if (ret)
			return ret;
	}

	ret = clk_set_rate(armclk, new_freq * 1000);
	if (ret)
		return ret;

	if (cpufreq.asyncclk) {
		ret = clk_set_rate(cpufreq.asyncclk, cpufreq.asyncrate);
		if (ret)
			return ret;
	}

	/* if moving to lower freq, lower the voltage after lowering freq */
	if (pdata->set_voltage && new_freq < old_freq)
		pdata->set_voltage(idx);

	return 0;
}

static int davinci_cpu_init(struct cpufreq_policy *policy)
{
	int result = 0;
	struct davinci_cpufreq_config *pdata = cpufreq.dev->platform_data;
	struct cpufreq_frequency_table *freq_table = pdata->freq_table;

	if (policy->cpu != 0)
		return -EINVAL;

	/* Finish platform specific initialization */
	if (pdata->init) {
		result = pdata->init();
		if (result)
			return result;
	}

	policy->clk = cpufreq.armclk;

	/*
	 * Time measurement across the target() function yields ~1500-1800us
	 * time taken with no drivers on notification list.
	 * Setting the latency to 2000 us to accommodate addition of drivers
	 * to pre/post change notification list.
	 */
	cpufreq_generic_init(policy, freq_table, 2000 * 1000);
	return 0;
}

static struct cpufreq_driver davinci_driver = {
	.flags		= CPUFREQ_NEED_INITIAL_FREQ_CHECK,
	.verify		= cpufreq_generic_frequency_table_verify,
	.target_index	= davinci_target,
	.get		= cpufreq_generic_get,
	.init		= davinci_cpu_init,
	.name		= "davinci",
};

static int __init davinci_cpufreq_probe(struct platform_device *pdev)
{
	struct davinci_cpufreq_config *pdata = pdev->dev.platform_data;
	struct clk *asyncclk;

	if (!pdata)
		return -EINVAL;
	if (!pdata->freq_table)
		return -EINVAL;

	cpufreq.dev = &pdev->dev;

Annotation

Implementation Notes