Re: [PATCH 2/2] xen: arm: more flexible scheme for specifying early printk device

[Ian Campbell <ian.campbell@citrix.com>]

On Wed, 2015-03-11 at 14:11 +0000, Ian Campbell wrote:

Sorry, I was too lazy to write a cover letter for these changes and
forgot that would mean that git send-email wouldn't thread them.

> This allows for early-printk to be specified (for existing UARTS at
> least) without the need to edit Rules.mk.
> 
> The existing shortcuts are retained, but in a much more compact
> fashion.
> 
> An unused EARLY_PRINTK_BAUD was removed from the zynqmq settings.
> 
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> ---
>  docs/misc/arm/early-printk.txt |   34 +++++++++---
>  xen/arch/arm/Rules.mk          |  114 ++++++++++++++--------------------------
>  2 files changed, 65 insertions(+), 83 deletions(-)
> 
> diff --git a/docs/misc/arm/early-printk.txt b/docs/misc/arm/early-printk.txt
> index 44df35e..7e03955 100644
> --- a/docs/misc/arm/early-printk.txt
> +++ b/docs/misc/arm/early-printk.txt
> @@ -7,8 +7,32 @@ Note that selecting this option will limit Xen to a single UART definition.
>  Attempting to boot Xen image on a different platform *will not work*, so this
>  option should not be enable for Xens that are intended to be portable.
>  
> -CONFIG_EARLY_PRINTK=mach
> -where mach is the name of the machine:
> +CONFIG_EARLY_PRINTK=<INC>,<BASE_ADDRESS>,<OTHER_OPTIONS>
> +
> +<INC> and <BASE_ADDRESS> are mandatory arguments:
> +
> +  - <INC> is the name of the driver, see xen/arch/arm/arm{32,64}/debug-*.inc
> +    (where <INC> corresponds to the wildcarded *).
> +  - <BASE_ADDRESS> is the base physical address of the UART to use
> +
> +<OTHER_OPTIONS> varies depending on <INC>:
> +
> +  - 8250,<BASE_ADDRESS>,<REG_SHIFT>
> +    - <REG_SHIFT> is, optionally, the left-shift to apply to the
> +      register offsets within the uart.
> +  - pl011,<BASE_ADDRESS>,<BAUD_RATE>
> +    - <BAUD_RATE> is, optionally a baud rate which should be used to
> +      configure the UART at start of day.
> +
> +      If <BAUD_RATE> is not given then the code will not try to
> +      initialize the UART, so that bootloader or firmware settings can
> +     be used for maximum compatibility.
> +  - For all other uarts there are no additional options.
> +
> +As a convenience it is also possible to select from a list of
> +predefined configurations using CONFIG_EARLY_PRINTK=mach where mach is
> +the name of the machine:
> +
>    - brcm: printk with 8250 on Broadcom 7445D0 boards with A15 processors.
>    - dra7: printk with 8250 on DRA7 platform
>    - exynos5250: printk with the second UART
> @@ -27,11 +51,7 @@ where mach is the name of the machine:
>    - xgene-storm: printk with 820 on Xgene storm platform
>    - zynqmp: printk with Cadence UART for Xilinx ZynqMP SoCs
>  
> -The base address and baud rate is hardcoded in xen/arch/arm/Rules.mk,
> +These settings are is hardcoded in xen/arch/arm/Rules.mk,
>  see there when adding support for new machines.
> -If not explicitly requested with "EARLY_PRINTK_INIT_UART := y" in Rules.mk,
> -the code will not try to initialize the UART, so that bootloader or
> -firmware settings can be used for maximum compatibility. The baud rate
> -parameter is ignored in this case.
>  
>  By default early printk is disabled.
> diff --git a/xen/arch/arm/Rules.mk b/xen/arch/arm/Rules.mk
> index af3448b..b45cb69 100644
> --- a/xen/arch/arm/Rules.mk
> +++ b/xen/arch/arm/Rules.mk
> @@ -42,84 +42,46 @@ EARLY_PRINTK := n
>  
>  ifeq ($(debug),y)
>  
> -ifeq ($(CONFIG_EARLY_PRINTK), brcm)
> -EARLY_PRINTK_INC := 8250
> -EARLY_UART_BASE_ADDRESS := 0xF040AB00
> -EARLY_UART_REG_SHIFT := 2
> -endif
> -ifeq ($(CONFIG_EARLY_PRINTK), dra7)
> -EARLY_PRINTK_INC := 8250
> -EARLY_UART_BASE_ADDRESS := 0x4806A000
> -EARLY_UART_REG_SHIFT := 2
> -endif
> -ifeq ($(CONFIG_EARLY_PRINTK), fastmodel)
> -EARLY_PRINTK_INC := pl011
> +# See docs/misc/arm/early-printk.txt for syntax
> +
> +EARLY_PRINTK_brcm           := 8250,0xF040AB00,2
> +EARLY_PRINTK_dra7           := 8250,0x4806A000,2
> +EARLY_PRINTK_fastmodel      := pl011,0x1c090000,115200
> +EARLY_PRINTK_exynos5250     := exynos4210,0x12c20000
> +EARLY_PRINTK_hip04-d01      := 8250,0xE4007000,2
> +EARLY_PRINTK_juno           := pl011,0x7ff80000
> +EARLY_PRINTK_lager          := scif,0xe6e60000
> +EARLY_PRINTK_midway         := pl011,0xfff36000
> +EARLY_PRINTK_omap5432       := 8250,0x48020000,2
> +EARLY_PRINTK_seattle        := pl011,0xe1010000
> +EARLY_PRINTK_sun6i          := 8250,0x01c28000,2
> +EARLY_PRINTK_sun7i          := 8250,0x01c28000,2
> +EARLY_PRINTK_thunderx       := pl011,0x87e024000000
> +EARLY_PRINTK_vexpress       := pl011,0x1c090000
> +EARLY_PRINTK_xgene-mcdivitt := 8250,0x1c021000,2
> +EARLY_PRINTK_xgene-storm    := 8250,0x1c020000,2
> +EARLY_PRINTK_zynqmp         := cadence,0xff000000
> +
> +COMMA := ,
> +ifneq ($(EARLY_PRINTK_$(CONFIG_EARLY_PRINTK)),)
> +EARLY_PRINTK_CFG := $(subst $(COMMA), ,$(EARLY_PRINTK_$(CONFIG_EARLY_PRINTK)))
> +else
> +EARLY_PRINTK_CFG := $(subst $(COMMA), ,$(CONFIG_EARLY_PRINTK))
> +endif
> +
> +# Extract configuration from string
> +EARLY_PRINTK_INC := $(word 1,$(EARLY_PRINTK_CFG))
> +EARLY_UART_BASE_ADDRESS := $(word 2,$(EARLY_PRINTK_CFG))
> +
> +# UART specific options
> +ifeq ($(EARLY_PRINTK_INC),8250)
> +EARLY_UART_REG_SHIFT := $(word 3,$(EARLY_PRINTK_CFG))
> +endif
> +ifeq ($(EARLY_PRINTK_INC),pl011)
> +ifneq ($(word 3,$(EARLY_PRINTK_CFG)),)
>  EARLY_PRINTK_INIT_UART := y
> -EARLY_PRINTK_BAUD := 115200
> -EARLY_UART_BASE_ADDRESS := 0x1c090000
> -endif
> -ifeq ($(CONFIG_EARLY_PRINTK), exynos5250)
> -EARLY_PRINTK_INC := exynos4210
> -EARLY_UART_BASE_ADDRESS := 0x12c20000
> -endif
> -ifeq ($(CONFIG_EARLY_PRINTK), hip04-d01)
> -EARLY_PRINTK_INC := 8250
> -EARLY_UART_BASE_ADDRESS := 0xE4007000
> -EARLY_UART_REG_SHIFT := 2
> -endif
> -ifeq ($(CONFIG_EARLY_PRINTK), juno)
> -EARLY_PRINTK_INC := pl011
> -EARLY_UART_BASE_ADDRESS := 0x7ff80000
> -endif
> -ifeq ($(CONFIG_EARLY_PRINTK), lager)
> -EARLY_PRINTK_INC := scif
> -EARLY_UART_BASE_ADDRESS := 0xe6e60000
> -endif
> -ifeq ($(CONFIG_EARLY_PRINTK), midway)
> -EARLY_PRINTK_INC := pl011
> -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), seattle)
> -EARLY_PRINTK_INC := pl011
> -EARLY_UART_BASE_ADDRESS := 0xe1010000
> -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
> -ifeq ($(CONFIG_EARLY_PRINTK), thunderx)
> -EARLY_PRINTK_INC := pl011
> -EARLY_UART_BASE_ADDRESS := 0x87e024000000
> -endif
> -ifeq ($(CONFIG_EARLY_PRINTK), vexpress)
> -EARLY_PRINTK_INC := pl011
> -EARLY_UART_BASE_ADDRESS := 0x1c090000
> -endif
> -ifeq ($(CONFIG_EARLY_PRINTK), xgene-mcdivitt)
> -EARLY_PRINTK_INC := 8250
> -EARLY_UART_BASE_ADDRESS := 0x1c021000
> -EARLY_UART_REG_SHIFT := 2
> -endif
> -ifeq ($(CONFIG_EARLY_PRINTK), xgene-storm)
> -EARLY_PRINTK_INC := 8250
> -EARLY_UART_BASE_ADDRESS := 0x1c020000
> -EARLY_UART_REG_SHIFT := 2
> +EARLY_PRINTK_BAUD := $(word 3,$(EARLY_PRINTK_CFG))
>  endif
> -ifeq ($(CONFIG_EARLY_PRINTK), zynqmp)
> -EARLY_PRINTK_INC := cadence
> -EARLY_PRINTK_BAUD := 115200
> -EARLY_UART_BASE_ADDRESS := 0xff000000
>  endif
>  
>  ifneq ($(EARLY_PRINTK_INC),)