The PLL converts a 26.6 MHz input clock to 87.8 MHz, which is later divided by two and becomes PCLK. (See comments below for details.) All this looks like a textbook example for platform stuff, but let's take it one step a time. Signed-off-by: Werner Almesberger --- Index: cam/drivers/media/video/samsung/4xa_sensor.c =================================================================== --- cam.orig/drivers/media/video/samsung/4xa_sensor.c 2009-03-10 02:28:49.000000000 +0800 +++ cam/drivers/media/video/samsung/4xa_sensor.c 2009-03-10 02:29:37.000000000 +0800 @@ -29,6 +29,27 @@ #include "../s3c_camif.h" #include "4xa_sensor.h" + +/* + * Samsung's original code: + * .camclk = 44000000, / * for 20 fps: 44MHz, for 12 fps (more + * stable): 26MHz * / + * + * Experimenting with the controls yielded the following: + * + * PLL_CLK gets divided according to TCMD.Div8_r (1,00h) and then by + * SEL_MAIN.Half_PCLK_Enable (5,8Fh) until it finally becomes PCLK. + * + * Div8_r = 0: 1/4, 1: 1/2 (default) + * Half_PCLK_Enable = 0: 1/1 (default), 1: 1/2 + * + * Thus our 26.6 MHz MCLK becomes an 87.78 MHz PLL_CLK and eventually a PCLK + * of 43.89 MHz. + */ + +#define CAMCLK 26600000 /* 26.6 MHz */ + + static struct i2c_driver sensor_driver; /* This is an abstract CIS sensor for MSDMA input. */ @@ -36,8 +57,7 @@ camif_cis_t msdma_input = { .itu_fmt = CAMIF_ITU601, .order422 = CAMIF_CBYCRY, /* another case: YCRYCB */ - .camclk = 44000000, /* for 20 fps: 44MHz, for 12 fps (more - stable): 26MHz */ + .camclk = CAMCLK, .source_x = 800, .source_y = 600, .win_hor_ofst = 0, @@ -54,8 +74,7 @@ camif_cis_t interlace_input = { .itu_fmt = CAMIF_ITU601, .order422 = CAMIF_CBYCRY, /* another case: YCRYCB */ - .camclk = 44000000, /* for 20 fps: 44MHz, for 12 fps (more - stable): 26MHz */ + .camclk = CAMCLK, .source_x = 800, .source_y = 600, .win_hor_ofst = 0, @@ -73,8 +92,7 @@ static camif_cis_t data = { .itu_fmt = CAMIF_ITU601, .order422 = CAMIF_YCBYCR, - .camclk = 44000000, /* for 20 fps: 44MHz, for 12 fps (more - stable): 26MHz */ + .camclk = CAMCLK, .source_x = 800, .source_y = 600, .win_hor_ofst = 0, --