Re: [Xen-devel] [PATCH V2 2/2] xen: arm: implement early prink for 8250 uart

[Chen Baozi <baozich@xxxxxxxxx>]

On Jul 3, 2013, at 9:38 PM, "Bamvor Jian Zhang" <bjzhang@xxxxxxxx> wrote:

> Hi, Ian
> 
>>>> Wrote "Ian Campbell <Ian.Campbell@xxxxxxxxxx>"> On Tue
>> On Tue, 2013-07-02 at 21:11 +0800, Bamvor Jian Zhang wrote:
>>> diff --git a/xen/arch/arm/arm32/debug-8250.inc 
>>> b/xen/arch/arm/arm32/debug-8250.inc
>>> new file mode 100644
>>> index 0000000..c11357d
>>> --- /dev/null
>>> +++ b/xen/arch/arm/arm32/debug-8250.inc
>>> @@ -0,0 +1,48 @@
>>> +/*
>>> + * xen/arch/arm/arm32/debug-8250.inc
>>> + *
>>> + * 8250 specific debug code
>>> + *
>>> + * Bamvor Jian Zhang <bjzhang@xxxxxxxx>
>>> + * Copyright (c) 2013 SUSE
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License as published by
>>> + * the Free Software Foundation; either version 2 of the License, or
>>> + * (at your option) any later version.
>>> + *
>>> + * This program is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> + * GNU General Public License for more details.
>>> + */
>>> +
>>> +
>>> +#define UART_TX           (0x00<<2)    /* Out: Transmit buffer */
>>> +#define UART_LSR          (0x05<<2)    /* In:  Line Status Register */
>> 
>> Is the shift 2 on Baozi's platform too? Perhaps this could be a #define
>> provided in the same style as EARLY_UART_BASE_ADDRESS or via some other
>> means?
>> 
>> The definitions themselves duplicate those in
>> xen/drivers/char/ns16550.c, perhaps we could refactor those into a
>> suitable header?
> yes. it should be. meanwhile considering the shift bit and other things. 
> i am not sure how to merge the headers until i got the ns16550 actual used by
> arm SOC. 
Actually, I've already modified ns16550 driver to work on my platform. And it 
also has the shift problem.

If you like, I could send a patch to refactor it, :-)

Baozi

> 
> Bamvor
>> 
>>> +
>>> +#define UART_LSR_THRE     0x20         /* Xmit holding register empty */
>>> +
>>> +/* 8250 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, #UART_LSR]    /* <- UART_LSR (Line Status 
>>> Register) */
>>> +        tst   \rc, #UART_LSR_THRE      /* Check BUSY bit */
>>> +        beq   1b                       /* Wait for the UART to be ready */
>>> +.endm
>>> +
>>> +/* 8250 UART transmit character
>>> + * rb: register which contains the UART base address
>>> + * rt: register which contains the character to transmit */
>>> +.macro early_uart_transmit rb, rt
>>> +        str   \rt, [\rb, #UART_TX]     /* -> UART_TX */
>>> +.endm
>>> +
>>> +/*
>>> + * Local variables:
>>> + * mode: ASM
>>> + * indent-tabs-mode: nil
>>> + * End:
>>> + */
> 
> 


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