2013/5/17 jean-philippe francois <jp.francois@xxxxxxxxxx>: > Hi, > > Laurent, you are on the recipient list because the symptom is visible > throug your driver. I found the other name looking in the clock > related files. Please apologize if you are not concerned by this mail. > > Symptom : > External clock CAM_XCLKA frequency is wrong with 3.9, it was ok until > 3.6. Everything else is working fine, except the fps are higher, and > the image quality sucks because the input clock is out of spec. > Oscilloscope measured freq is around 30 MHz instead of the 24 MHz the > sensor is asking for. > > Hardware : > dm3730, with 19.2 MHz crystal, running at OPP100 > > The register frequency settings seems to be ok, and they are the same > as in 3.6.11 : > CM_CLKSEL2_PLL : 0x04816807 > 19, 2 * 360 / 8 = 864 MHz > this value is already set when I look at it in u-boot > > CM_CLKSEL_CAM : 0x5 > 864 / 5 = 172,8 MHz > this value is set through the clock framework by the omap3isp > driver code > > ISP.TCTRL_CTRL : 0x7 > 172,8 / 7 = 24,685... MHz > this value is set by the omap3isp driver code > > However, as stated before, the actual output frequency is NOT 24 MHz > but around 30. > > If dpll4 frequency is wrong, what other clock would be affected ? As usual, writing a mail brings up new idea. Sorry to use the lists as rubber duck debug partner, but I still need your help. Obviously, dpll4 frequency is correct, because it sources the 96 and 48 MHz clock. I can check it measuring bit time on uart3tx : 8.6usec for 115200 => Ok 30 MHz is 1.25 * 24 MHz CM_CLKSEL_CAM reset value is 4, programmed value is 5, So I did the following, while looking at CAM_XCLKA on scope : # devmem 0x48004f40 0x00000005 # devmem 0x48004f40 32 5 -> freq = 30 MHz # devmem 0x48004f40 32 4 -> freq = 30 MHz # devmem 0x48004f40 32 5 -> freq = 24 MHz So there is something nasty in the setup sequence of cam_mclk and dpll4_m5ckx2 that prevents the new divisor value to be used by the hardware. I will dive into the code to see where things went wrong, but I am a bit lost here. > What can I do to debug this ? > Laurent, I believe you have a camera add-on board for the beagle xm, > could you test and report wether you can reproduce this bug ? > > Attached is the boot log with 3.9, with some debugging messages activated. > > Thank you for your help, > Regards, > > Jean-Philippe François -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
