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i2c: bcm2835: Add support for dynamic clock 

Support a dynamic clock by reading the frequency and setting the
divisor in the transfer function instead of during probe.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Noralf Trønnes 2016-10-03 22:06:14 +02:00 committed by Wolfram Sang
parent e13e19e12f
commit 9446f62e8e
1 changed files with 32 additions and 19 deletions
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51
drivers/i2c/busses/i2c-bcm2835.c
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@ -58,6 +58,7 @@ struct bcm2835_i2c_dev {
void __iomem *regs; void __iomem *regs;
struct clk *clk; struct clk *clk;
int irq; int irq;
u32 bus_clk_rate;
struct i2c_adapter adapter; struct i2c_adapter adapter;
struct completion completion; struct completion completion;
struct i2c_msg *curr_msg; struct i2c_msg *curr_msg;
@ -78,6 +79,30 @@ static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
return readl(i2c_dev->regs + reg); return readl(i2c_dev->regs + reg);
} }
static int bcm2835_i2c_set_divider(struct bcm2835_i2c_dev *i2c_dev)
{
u32 divider;
divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk),
i2c_dev->bus_clk_rate);
/*
* Per the datasheet, the register is always interpreted as an even
* number, by rounding down. In other words, the LSB is ignored. So,
* if the LSB is set, increment the divider to avoid any issue.
*/
if (divider & 1)
divider++;
if ((divider < BCM2835_I2C_CDIV_MIN) ||
(divider > BCM2835_I2C_CDIV_MAX)) {
dev_err_ratelimited(i2c_dev->dev, "Invalid clock-frequency\n");
return -EINVAL;
}
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
return 0;
}
static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev) static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
{ {
u32 val; u32 val;
@ -224,7 +249,7 @@ static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
{ {
struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap); struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
unsigned long time_left; unsigned long time_left;
int i; int i, ret;
for (i = 0; i < (num - 1); i++) for (i = 0; i < (num - 1); i++)
if (msgs[i].flags & I2C_M_RD) { if (msgs[i].flags & I2C_M_RD) {
@ -233,6 +258,10 @@ static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
return -EOPNOTSUPP; return -EOPNOTSUPP;
} }
ret = bcm2835_i2c_set_divider(i2c_dev);
if (ret)
return ret;
i2c_dev->curr_msg = msgs; i2c_dev->curr_msg = msgs;
i2c_dev->num_msgs = num; i2c_dev->num_msgs = num;
reinit_completion(&i2c_dev->completion); reinit_completion(&i2c_dev->completion);
@ -282,7 +311,6 @@ static int bcm2835_i2c_probe(struct platform_device *pdev)
{ {
struct bcm2835_i2c_dev *i2c_dev; struct bcm2835_i2c_dev *i2c_dev;
struct resource *mem, *irq; struct resource *mem, *irq;
u32 bus_clk_rate, divider;
int ret; int ret;
struct i2c_adapter *adap; struct i2c_adapter *adap;
@ -306,28 +334,13 @@ static int bcm2835_i2c_probe(struct platform_device *pdev)
} }
ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency", ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
&bus_clk_rate); &i2c_dev->bus_clk_rate);
if (ret < 0) { if (ret < 0) {
dev_warn(&pdev->dev, dev_warn(&pdev->dev,
"Could not read clock-frequency property\n"); "Could not read clock-frequency property\n");
bus_clk_rate = 100000; i2c_dev->bus_clk_rate = 100000;
} }
divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), bus_clk_rate);
/*
* Per the datasheet, the register is always interpreted as an even
* number, by rounding down. In other words, the LSB is ignored. So,
* if the LSB is set, increment the divider to avoid any issue.
*/
if (divider & 1)
divider++;
if ((divider < BCM2835_I2C_CDIV_MIN) ||
(divider > BCM2835_I2C_CDIV_MAX)) {
dev_err(&pdev->dev, "Invalid clock-frequency\n");
return -ENODEV;
}
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0); irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
if (!irq) { if (!irq) {
dev_err(&pdev->dev, "No IRQ resource\n"); dev_err(&pdev->dev, "No IRQ resource\n");