[RFC 1/4] rtc: support for amlogic meson rtc

[Neil Armstrong]

Hi Ben,

On 06/23/2016 10:21 PM, Ben Dooks wrote:
> Add support for the AMLogic meson8b/meson6 RTC block.
> 
> Signed-off-by: Ben Dooks <ben.dooks at codethink.co.uk>
> ---

[...]

> +
> +/* registers accessed from cpu bus */
> +#define RTC_REG(x)	((x) * 4)	/* rtc registers 0-4 */
> +
> +#define LINE_SDI	(1 << 2)
> +#define LINE_SEN	(1 << 1)
> +#define LINE_SCLK	(1 << 0)
> +
> +#define RTCREG0_START_SER	BIT(17)
> +#define RTCREG0_WAIT_SER	BIT(22)
> +
> +#define RTCREG1_READY	BIT(1)
> +
> +/* rtc registers accessed via rtc-serial inteface */
> +#define RTC_COUNTER		(0)
> +#define RTC_SEC_ADJ		(2)
> +
> +#define RTC_ADDR_BITS		(3)	/* number of address bits to send */
> +#define RTC_DATA_BITS		(32)	/* number of data bits to tx/rx */
> +
> +#define MESON_STATIC_BIAS_CUR	(0x5 << 1)
> +#define MESON_STATIC_VOLTAGE	(0x3 << 11)

Cleanup indentation here.

> +
> +struct meson_rtc {
> +	struct rtc_device	*rtc;	/* rtc device we created */
> +	struct device		*dev;	/* device we bound from */
> +	struct reset_control	*reset;	/* reset source */
> +	struct mutex		lock;	/* rtc lock */
> +	void __iomem		*regs;	/* rtc register access */
> +};
> +
> +static void meson_rtc_setline(struct meson_rtc *rtc, unsigned bit, unsigned to)
> +{
> +	u32 reg0;
> +
> +	reg0 = readl(rtc->regs + RTC_REG(0));
> +	if (to)
> +		reg0 |= bit;
> +	else
> +		reg0 &= ~bit;
> +	writel(reg0, rtc->regs + RTC_REG(0));
> +	
> +}
> +
> +static void meson_rtc_sclk_pulse(struct meson_rtc *rtc)
> +{
> +	udelay(5);
> +	meson_rtc_setline(rtc, LINE_SCLK, 0);
> +	udelay(5);
> +	meson_rtc_setline(rtc, LINE_SCLK, 1);
> +}
> +
> +static void meson_rtc_send_bit(struct meson_rtc *rtc, unsigned bit)
> +{
> +	meson_rtc_setline(rtc, LINE_SDI, bit ? 1 : 0);

You can use !!bit here also

> +	meson_rtc_sclk_pulse(rtc);
> +}
> +
> +static void meson_rtc_send_bits(struct meson_rtc *rtc, u32 data, unsigned nr)
> +{
> +	u32 bit = 1 << (nr - 1);
> +	
> +	while (bit) {
> +		meson_rtc_send_bit(rtc, data & bit);
> +		bit >>= 1;
> +	}
> +}
> +
> +static void meson_rtc_set_dir(struct meson_rtc *rtc, u32 mode)
> +{
> +	meson_rtc_setline(rtc, LINE_SDI, 0);
> +	meson_rtc_send_bit(rtc, mode);
> +	meson_rtc_setline(rtc, LINE_SDI, 0);
> +}
> +
> +static u32 meson_rtc_read_sdo(struct meson_rtc *rtc)
> +{
> +	return readl(rtc->regs + RTC_REG(1)) & (1 << 0);

Drop the << 0 here, or replace by BIT(0)

> +}
> +
> +static u32 meson_rtc_get_data(struct meson_rtc *rtc)
> +{
> +	u32 val = 0;
> +	int bit;
> +
> +	for (bit = 0; bit < RTC_DATA_BITS; bit++) {
> +		meson_rtc_sclk_pulse(rtc);
> +		val <<= 1;
> +		val |= meson_rtc_read_sdo(rtc);
> +	}
> +
> +	return val;
> +}
> +
> +static int meson_rtc_wait_bus(struct meson_rtc *rtc, unsigned timeout_ms)
> +{
> +	unsigned long timeout = jiffies + msecs_to_jiffies(timeout_ms);
> +	u32 val;
> +
> +	val = readl(rtc->regs + RTC_REG(0));
> +	val &= ~(LINE_SDI | LINE_SEN | LINE_SCLK);
> +	writel(val, rtc->regs + RTC_REG(0));
> +
> +	while (time_before(jiffies, timeout)) {
> +		val = readl(rtc->regs + RTC_REG(1));
> +		if (val & RTCREG1_READY)
> +			return 1;
> +
> +		dev_info(rtc->dev, "%s: reg1=%08x\n", __func__, val);
> +		msleep(10);
> +	}
> +
> +	return 0;
> +}
> +
> +static int meson_rtc_get_bus(struct meson_rtc *rtc)
> +{
> +	int ret, retries = 3;
> +
> +	while (retries) {
> +		if (meson_rtc_wait_bus(rtc, 300))
> +			return 0;

Put the timeout time in a define 300 to be easily changed.

> +
> +		dev_warn(rtc->dev, "failed to get bus, re-setting\n");
> +
> +		retries--;
> +		ret = reset_control_reset(rtc->reset);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	dev_err(rtc->dev, "%s: bus is not ready\n", __func__);
> +	return -ETIMEDOUT;
> +}
> +
> +static int meson_rtc_read(struct meson_rtc *rtc, unsigned int reg, u32 *data)
> +{
> +	int ret;
> +
> +	ret = meson_rtc_get_bus(rtc);
> +	if (ret)
> +		return ret;
> +
> +	meson_rtc_setline(rtc, LINE_SEN, 1);
> +	meson_rtc_send_bits(rtc, reg, RTC_ADDR_BITS);
> +	meson_rtc_setline(rtc, LINE_SEN, 0);
> +	meson_rtc_set_dir(rtc, 0);
> +	*data = meson_rtc_get_data(rtc);
> +
> +	return 0;
> +}
> +
> +static int meson_rtc_write(struct meson_rtc *rtc, unsigned int reg, u32 data)
> +{
> +	int ret;
> +
> +	ret = meson_rtc_get_bus(rtc);
> +	if (ret)
> +		return ret;
> +
> +	meson_rtc_setline(rtc, LINE_SEN, 1);
> +	meson_rtc_send_bits(rtc, reg, RTC_ADDR_BITS);
> +	meson_rtc_setline(rtc, LINE_SEN, 0);
> +	meson_rtc_set_dir(rtc, 1);
> +	meson_rtc_send_bits(rtc, data, RTC_DATA_BITS);
> +
> +	return 0;
> +}
> +
> +static int meson_rtc_gettime(struct device *dev, struct rtc_time *tm)
> +{
> +	struct meson_rtc *rtc = dev_get_drvdata(dev);
> +	int ret;
> +	u32 time;
> +
> +	mutex_lock(&rtc->lock);
> +
> +	ret = meson_rtc_read(rtc, RTC_COUNTER, &time);
> +	if (ret)
> +		return ret;
> +
> +	rtc_time_to_tm(time, tm);
> +	dev_info(dev, "read time %lu\n", (unsigned long)time);

Replace by a dev_dbg here.

> +	
> +	mutex_unlock(&rtc->lock);
> +	return 0;
> +}
> +
> +static int meson_rtc_settime(struct device *dev, struct rtc_time *tm)
> +{
> +	struct meson_rtc *rtc = dev_get_drvdata(dev);
> +	unsigned long time;
> +	int ret;
> +	
> +	mutex_lock(&rtc->lock);
> +
> +	rtc_tm_to_time(tm, &time);
> +	ret = meson_rtc_write(rtc, RTC_COUNTER, time);
> +	
> +	mutex_unlock(&rtc->lock);
> +	return ret;
> +}
> +
> +static const struct rtc_class_ops meson_rtc_ops = {
> +	.read_time	= meson_rtc_gettime,
> +	.set_time	= meson_rtc_settime,
> +};
> +
> +static int meson_rtc_wait_serialiser(struct meson_rtc *rtc)
> +{
> +	unsigned long timeout = jiffies + msecs_to_jiffies(100);
> +
> +	while (time_before(jiffies, timeout)) {
> +		if (!(readl(rtc->regs + RTC_REG(0)) & RTCREG0_WAIT_SER))
> +			return 0;
> +		msleep(10);
> +	}
> +
> +	return -ETIMEDOUT;
> +}
> +
> +static int meson_rtc_write_static(struct meson_rtc *rtc, u32 data)
> +{
> +	u32 tmp;
> +
> +	mutex_lock(&rtc->lock);
> +
> +	writel(data >> 8, rtc->regs + RTC_REG(4));
> +
> +	tmp = readl(rtc->regs + RTC_REG(0));
> +	tmp &= ~(0xff << 24);
> +	tmp |= (data << 24);
> +	tmp |= RTCREG0_START_SER;

Add a define for the shifts here.

> +
> +	writel(tmp, rtc->regs + RTC_REG(0));
> +
> +	if (meson_rtc_wait_serialiser(rtc))
> +		return -ETIMEDOUT;
> +
> +	dev_info(rtc->dev, "rtc_reg0 = %08x\n", readl(rtc->regs + RTC_REG(0)));
> +	mutex_unlock(&rtc->lock);
> +

dev_dbg instead here.

> +	return 0;
> +}
> +
> +static int meson_rtc_probe(struct platform_device *pdev)
> +{
> +	struct meson_rtc *rtc;
> +	struct device *dev = &pdev->dev;
> +	struct resource *res;
> +	u32 tm;
> +	int ret;
> +	
> +	rtc = devm_kzalloc(dev, sizeof(struct meson_rtc), GFP_KERNEL);
> +	if (!rtc) {
> +		dev_err(dev, "failed to allocate memory\n");
> +		return -ENOMEM;
> +	}
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	rtc->regs = devm_ioremap_resource(dev, res);
> +	rtc->dev = dev;
> +
> +	if (IS_ERR(rtc->regs))
> +		return PTR_ERR(rtc->regs);
> +	
> +	mutex_init(&rtc->lock);
> +	platform_set_drvdata(pdev, rtc);
> +
> +	ret = meson_rtc_write_static(rtc,
> +				     MESON_STATIC_BIAS_CUR | MESON_STATIC_VOLTAGE);
> +	if (ret) {
> +		dev_err(dev, "failed to set static values\n");
> +		return ret;
> +	}
> +
> +	rtc->reset = devm_reset_control_get(dev, NULL);
> +	if (IS_ERR(rtc->reset))
> +		dev_warn(dev, "no reset available, rtc may not work\n");
> +
> +	/* check if we can read RTC counter, if not then the RTC is probably
> +	 * not functional. If it isn't probably best to not bind */
> +	ret = meson_rtc_read(rtc, RTC_COUNTER, &tm);
> +	if (ret) {
> +		dev_err(dev, "cannot read RTC counter, RTC not functional\n");
> +		return ret;
> +	}
> +
> +	rtc->rtc = devm_rtc_device_register(dev, "meson",
> +					    &meson_rtc_ops, THIS_MODULE);
> +	if (IS_ERR(rtc->rtc)) {
> +		dev_err(dev, "cannot attach rtc\n");
> +		return PTR_ERR(rtc->rtc);
> +	}
> +
> +	dev_info(dev, "device registered\n");
> +	return 0;
> +}
> +
> +static const struct of_device_id meson_rtc_dt_match[] = {
> +	{ .compatible = "amlogic,meson6-rtc", },
> +	{ .compatible = "amlogic,meson8-rtc", },
> +	{ .compatible = "amlogic,meson8b-rtc", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, meson_rtc_dt_match);
> +
> +static struct platform_driver meson_rtc_driver = {
> +	.probe		= meson_rtc_probe,
> +	.driver		= {
> +		.name	= "meson-rtc",
> +		.of_match_table	= of_match_ptr(meson_rtc_dt_match),
> +	},
> +};
> +module_platform_driver(meson_rtc_driver);
> +
> +MODULE_DESCRIPTION("AMLogic MESON RTC Driver");
> +MODULE_AUTHOR("Ben Dooks <ben.doosk at codethink.co.uk>");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:meson-rtc");
> 


Neil