Re: [Xen-devel] [PATCH 2/4] xen/arm: introduce Allwinner sun6i SOC basic support

["Bamvor Jian Zhang" <bjzhang@xxxxxxxx>]

"Ian Campbell <Ian.Campbell@xxxxxxxxxx>"> On Tue, 2013-06-18 at 00:35 -0600, 
Bamvor Jian Zhang wrote:
>> > This does appear to use a distinct set of registers from either the 
>> > existing pl011 or exynos4xxx UART driver so it should be a separate 
>> > driver. Do you know if this particular logic block is specific to sn6i 
>> > or is it used elsewhere (e.g. in all sun*i)? Do you know if there is a 
>> > more generic name for the part? 
>> sun4i, sun5i use the Synopsys DesignWare 8250 IP. and sun6i is also the 
>> 8250 compatiblity one. how about i create a debug-8250.inc and update 
>> it when other 8250 device add.
>  
> Yes if this is an 8250 compatible implementation the debug-8250.inc is 
> the right answer.
>  
> OOI Did you find the UART easily available on your platform? IOW was 
> soldering required...
i use the mele M9 STB which include the same connector of uart as mele
A1000.
>> > Not a big deal -- we can always rename to be more generic as we see 
>> > other examples of the same UART. 
>> > 
>> >> + * rb: register which contains the UART base address 
>> >> + * rc: scratch register 1 (unused here) 
>> >> + * rd: scratch register 2 (unused here) */ 
>> >> +.macro early_uart_init rb, rc, rd 
>> >> +/* assume the uart already init by bootloader */ 
>> >> +.endm 
>> > 
>> > I think Andre's refactoring of the UART init stuff in and around commit 
>> > 130645eee340608c12b632535d3f983508348ba1 lets you avoid this by just not 
>> > setting EARLY_PRINTK_INIT_UART.
>  
>> yes. I saw Andre' patch. when i write this piece of code Andre's patch is 
>> not commit. i will modify this in next version.
>  
> Thanks.
>  
>> > 
>> >> + 
>> >> +/* sun6i UART wait UART to be ready to transmit 
>> >> + * rb: register which contains the UART base address 
>> >> + * rc: scratch register */ 
>> >> +.macro early_uart_ready rb, rc 
>> >> +1: 
>> >> +        ldr   \rc, [\rb, #0x7c]     /* <- UART_USR (Status Register) */
>  
> I think this register is a designware extension to the 8250. The Linux 
> sunxi debug driver is instead checking the UART_LSR for the TEMT or THRE 
> bits.
>  
>> >> +        tst   \rc, #0x2             /* Check BUSY bit */ 
>> >> +        beq   1b                    /* Wait for the UART to be ready */ 
>> >> +.endm
>  
> Ian. 



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