On Friday, July 29, 2011 08:55:14 AM Jason Hui wrote:
Hi, Marek,
On Thu, Jul 14, 2011 at 5:58 AM, Marek Vasut marek.vasut@gmail.com wrote:
Rewrite the mxc_i2c driver.
- This version is much closer to Linux implementation.
- Fixes IPG_PERCLK being incorrectly used as clock source
- Fixes behaviour of the driver on iMX51
- Clean up coding style a bit ;-)
why you change i2c clock from IPG_PERCLK to IPG_CLK?
On MX51, PERCLK are those fast (680MHz) clock, that's not source of clock for I2C. The IPG_CLK (they are 68.5MHz iirc) are source for the I2C. Also, I discussed this with Stefano and we agreed this is likely a bug.
[...]
+static void i2c_imx_set_clk(unsigned int rate) {
int freq;
struct mxc_i2c_regs *i2c_regs = (struct mxc_i2c_regs *)I2C_BASE;unsigned int i2c_clk_rate;unsigned int div; int i;/* Divider value calculation */#if defined(CONFIG_MX31) struct clock_control_regs *sc_regs = (struct clock_control_regs *)CCM_BASE;
freq = mx31_get_ipg_clk();
i2c_clk_rate = mx31_get_ipg_clk(); /* start the required I2C clock */ writel(readl(&sc_regs->cgr0) | (3 << I2C_CLK_OFFSET), &sc_regs->cgr0);#else
freq = mxc_get_clock(MXC_IPG_PERCLK);
i2c_clk_rate = mxc_get_clock(MXC_IPG_CLK);#endif
There are two clocks for i2c:
Peripheral clock (IPBus): source from ipg_clk_root, which is for IP bus register read/write. Block clock: source from perclk_root, which is I2C function clock.
We need get perclk not ipg clock, right?
For divider, we need those slower ones, the IPG_CLK, not PERCLK.
BTW, do you test this driver on mx53?
No, I don't have one.
Jason