Two questions about porting linux2.6.22 to s3c2440 are provided.

For two questions about porting linux2.6.22 to s3c2440, please refer to-Linux general technology-Linux programming and kernel information. The following is a detailed description. 1. now the Linux kernel can be started normally, and the serial port is also normal, but the output CPU clock frequency is 200 HZ during startup, and I set 400 HZ in UBOOT, so I found the s3c244x_init_clocks function in the kernel and called the s3c2410_get_pll function. I found that in the s3c2410_get_pll function, the kernel formula for calculating FCLK is calculated using the s3c2410 formula, therefore, the frequency is calculated as 200 HZ, and the other ratio is still read at. so I modified the formula correctly and found that the serial port cannot be properly displayed when the kernel is started, how can this problem be solved? the port fails to find the setting of the serial port baud rate.
2. after porting the UDA audio card driver, I can make sound normally. However, I used the player in QTOPIA2.0 to play music. I found that the sound was very choppy and the playback speed of the player was very slow, it takes two to three seconds for the player to take a second in normal cases. I don't know if it is related to the sound card driver or the program itself.
The above two problems have been found on the internet and no proper solution has been found. please have some experience to point out the key points. thank you.