On Thu, Sep 15, 2011 at 3:39 AM, Marek Vasut marek.vasut@gmail.com wrote:
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?
[...]
Ok, I investigated a bit deeper and I suspect the clock.c is the culprit.
Apparently, the PERCLK doesn't run at the frequency the clock.c reports it runs on. Therefore, the i2c miscalculates the divider etc -- falling crap model (waterfall model).
But apparently, the i2c function clock should be IPG_PERCLK not IPG clock. And Linux also fix it already.
commit 9d73242458d9a2fe26e2e240488063d414eacb1c Author: Lothar Waßmann LW@KARO-electronics.de Date: Mon Jul 4 15:52:17 2011 +0200
mach-mx5: fix the I2C clock parents
The clock from which the I2C timing is derived is the ipg_perclk not ipg_clk.
I2C bus frequency was lower by a factor of ~8 due to the clock divider calculation being based on 66.5MHz IPG clock while the bus actually uses 8MHz ipg_perclk.
Kernel version: 3.0.0-rc2 branch 'imx-for-next' of git://git.pengutronix.de/git/imx/linux-2.6
Signed-off-by: Lothar Waßmann LW@KARO-electronics.de Signed-off-by: Sascha Hauer s.hauer@pengutronix.de
Anyway, Jason, can you look into that clock problem? I think there are more than just perclk miscalculated.
OK, I will check that part.
Jason
Cheers