Hi Wolfgang,
On Fri, Apr 1, 2011 at 1:35 PM, Wolfgang Denk wd@denx.de wrote:
Dear Lei Wen,
In message AANLkTi=BbS7wzcbsH26Hb0y_GVXzHtEQspoVZkKn1PMU@mail.gmail.com you wrote:
Can you please explain on what board, and with which tool chain, you see any problems?
I test on Marvell pxa955 (MG1) board, with android 4.4.0 toolchain. The pxa955's ns16550 register's IER has nine bits. The 8th bit is HSE, which means the high speed mode. It seems something wrong there, if access the ier by byte, the 8th bit would be 1 at the beginning, and would be cleared by the following set value in the ns16550 driver, which cause problem on that board, for the baudrate would be dysfunction.
This makes no sense to me. I have never seen any 9 bit registers in any processor I ever encountered in real life.
I don't mean that register is 9bit... I means that register, IER, is 32bit long, but 9-31th bit is reserved, and 0th to 8th bit is used... Maybe I don't say clearly... So byte access would only cover 0-7th bit, while 8th bit is not covered.
Also, in this case the serial controller is probably not NS16550 compatible, because AFAICT the NS16550 uses only 8 bit wide registers.
This is may be additional feature added. For another part except this one bit is all compatible with ns16550.
Best regards, Lei