Hi, Arnd, On 2016年09月07日 22:52, Arnd Bergmann wrote: > On Wednesday, September 7, 2016 9:33:53 PM CEST Zhichang Yuan wrote: >> From: "zhichang.yuan" <yuanzhich...@hisilicon.com> >> >> This patch support the earlycon for UART connected to LPC on Hip06. >> This patch is depended on the LPC driver. >> >> Signed-off-by: zhichang.yuan <yuanzhich...@hisilicon.com> >> > > I'm skeptical about this too. Is this just needed because the 8250 > earlycon support comes before the lpc bus initialization? I think you wonder why early_serial8250_setup can not be used direclty for this earlycon of LPC uart.
1. the earlycon kernel parameter format of LPC uart is different from 8250. something like that "earlycon=hisilpcuart,mmio,0xa01b0000,0,0x2f8". You see, there is one more parameter after the baudrate. Hip06 LPC uart need two base addresses for earlycon. 2. the IO type is mmio to introduce a memory base address to access LPC register file. But the real uart IO type is UPIO_PORT. This is spcial... 3. Just as your guess, earlycon should be earlier than lpc initialization. Best, Zhichang > > Could we start the LPC driver earlier to work around that? > > Arnd >
