Re: [Xen-devel] [PATCH v6 2/6] xen/arm: add 8250 compatible UART support for early_printk

[Chen Baozi <baozich@xxxxxxxxx>]

On Aug 12, 2013, at 11:16 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:

> On 08/09/2013 03:20 AM, Chen Baozi wrote:
>> Both OMAP5 and sun6i/sun7i SoCs share this UART driver for early_printk.
>> 
>> Signed-off-by: Chen Baozi <baozich@xxxxxxxxx>
>> ---
>> docs/misc/arm/early-printk.txt    |  3 +++
>> xen/arch/arm/Rules.mk             | 16 +++++++++++++++
>> xen/arch/arm/arm32/debug-8250.inc | 41 
>> +++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 60 insertions(+)
>> create mode 100644 xen/arch/arm/arm32/debug-8250.inc
>> 
>> diff --git a/docs/misc/arm/early-printk.txt b/docs/misc/arm/early-printk.txt
>> index fbc3208..1431751 100644
>> --- a/docs/misc/arm/early-printk.txt
>> +++ b/docs/misc/arm/early-printk.txt
>> @@ -13,6 +13,9 @@ where mach is the name of the machine:
>>   - exynos5250: printk with the second UART
>>   - midway: printk with the pl011 on Calxeda Midway processors
>>   - fastmodel: printk on ARM Fastmodel software emulators
>> +  - omap5432: printk with UART3 on TI OMAP5432 processors
>> +  - sun6i: printk with 8250 on Allwinner A31 processors
>> +  - sun7i: printk with 8250 on Allwinner A20 processors
>> 
>> The base address and baud rate is hardcoded in xen/arch/arm/Rules.mk,
>> see there when adding support for new machines.
>> diff --git a/xen/arch/arm/Rules.mk b/xen/arch/arm/Rules.mk
>> index a18e7fd..c5720fe 100644
>> --- a/xen/arch/arm/Rules.mk
>> +++ b/xen/arch/arm/Rules.mk
>> @@ -64,6 +64,21 @@ EARLY_PRINTK_INC := pl011
>> EARLY_PRINTK_BAUD := 115200
>> EARLY_UART_BASE_ADDRESS := 0xfff36000
>> endif
>> +ifeq ($(CONFIG_EARLY_PRINTK), omap5432)
>> +EARLY_PRINTK_INC := 8250
>> +EARLY_UART_BASE_ADDRESS := 0x48020000
>> +EARLY_UART_REG_SHIFT := 2
>> +endif
>> +ifeq ($(CONFIG_EARLY_PRINTK), sun6i)
>> +EARLY_PRINTK_INC := 8250
>> +EARLY_UART_BASE_ADDRESS := 0x01c28000
>> +EARLY_UART_REG_SHIFT := 2
>> +endif
>> +ifeq ($(CONFIG_EARLY_PRINTK), sun7i)
>> +EARLY_PRINTK_INC := 8250
>> +EARLY_UART_BASE_ADDRESS := 0x01c28000
>> +EARLY_UART_REG_SHIFT := 2
>> +endif
> 
> If the shift is the same for all UART based on 8250, you can simply
> define EARLY_UART_... in debug-8250.inc.

Though the shifts are all 2 so far, I cannot make sure that all UART
based on 8250 are the same, considering the original 8250 doesn't
need the shift...

> 
>> ifneq ($(EARLY_PRINTK_INC),)
>> EARLY_PRINTK := y
>> @@ -74,4 +89,5 @@ CFLAGS-$(EARLY_PRINTK_INIT_UART) += 
>> -DEARLY_PRINTK_INIT_UART
>> CFLAGS-$(EARLY_PRINTK) += 
>> -DEARLY_PRINTK_INC=\"debug-$(EARLY_PRINTK_INC).inc\"
>> CFLAGS-$(EARLY_PRINTK) += -DEARLY_PRINTK_BAUD=$(EARLY_PRINTK_BAUD)
>> CFLAGS-$(EARLY_PRINTK) += 
>> -DEARLY_UART_BASE_ADDRESS=$(EARLY_UART_BASE_ADDRESS)
>> +CFLAGS-$(EARLY_PRINTK) += -DEARLY_UART_REG_SHIFT=$(EARLY_UART_REG_SHIFT)
>> endif
>> diff --git a/xen/arch/arm/arm32/debug-8250.inc 
>> b/xen/arch/arm/arm32/debug-8250.inc
>> new file mode 100644
>> index 0000000..eb25882
>> --- /dev/null
>> +++ b/xen/arch/arm/arm32/debug-8250.inc
>> @@ -0,0 +1,41 @@
>> +/*
>> + * xen/arch/arm/arm32/debug-8250.inc
>> + *
>> + * 8250 specific debug code
>> + *
>> + * 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.
>> + */
>> +
>> +#include <xen/8250-uart.h>
>> +
>> +/* 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 << EARLY_UART_REG_SHIFT)] /* Read LSR */
>> +    tst     \rc, #UART_LSR_THRE     /* Check Xmit holding register flag */
>> +    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_THR]      /* Write Transmit buffer */
>> +.endm
>> +
>> +/*
>> + * Local variables:
>> + * mode: ASM
>> + * indent-tabs-mode: nil
>> + * End:
>> + */
>> 
> 
> 
> -- 
> Julien Grall


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