Hi Vineet, Alexey, Arnd, On Thu, 2016-03-10 at 09:55 +0000, Vineet Gupta wrote:
Can you or Lada provide more details as to exactly what is not working - what driver to be precise 8250 or dw-8250. And where exactly the failure shows up. I want to understand this more Noam told me off list that he has no issues with both big endian ARC + 8250 in systemc model or silicon. -Vineet Driver is 8250, kernel is built for BE arc, nsim option in model "nsim_isa_big_endian = 1". With current "readl" and "writel" implementation for ARC we read word from memory without any endianess manipulation. So in case of little endian architecture we get what we want: the first memory byte is the low byte in the word. But in case of big endian architecture the word endianess is swapped: the first memory byte is the high word byte. And for example, let's see what happens when we use "readl" in function "serial8250_early_in" in driver/tty/serial/8250. Take a look to one line from memory dump: 0xf0000010: 0x0b 0x00 0x00 0x00 0x60 0x00 0x00 0x00 When kernel is built for little endian architecture, we read this data in status register in function "serial_putc" using "readl" function in driver/tty/serial/8250 as: r0: 0x0000006 The low byte is 0x0b, so the condition "if ((status & BOTH_EMPTY) == BOTH_EMPTY)" is true, as BOTH_EMPTY is some mask with low bytes set. When kernel is built with "CPU_BIG_ENDIAN" and model nsim option is "nsim_isa_big_endian=1", we read this data as: r0: 0x6000000 So as you can see the low byte is 0x00 and above mentioned condition never becomes true, we can't continue initialization. Regards, Lada _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
