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ARC: [axs101] support early 8250 uart 

Earlycon calculates UART clock as "BASE_BAUD * 16". In case of ARC
"BASE_BAUD" is calculated dynamically in runtime, basically it is an
alias to arc_early_base_baud(), which in turn just does
"arc_base_baud/16".

8250 UART on AXS/SDP board uses 33.3MHz clock source which is set in
"arc_base_baud" with this change.

Additional compatibility string "snps,arc-sdp" is introduced as well
because there're different flavours of AXS boards but they all share the
same motherboard and so it's possible to re-use the same code for
motherbord even if CPU daughterboard changes.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
hifive-unleashed-5.1
Vineet Gupta 2015-02-02 19:23:21 +05:30
parent 556cc1c5f5
commit 8d0d56ba24
3 changed files with 5 additions and 3 deletions
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2
Documentation/devicetree/bindings/arc/axs101.txt
View File

@ -4,4 +4,4 @@ Synopsys DesignWare ARC Software Development Platforms Device Tree Bindings
SDP Main Board with an AXC001 CPU Card hoisting ARC700 core in silicon
Required root node properties:
- compatible = "snps,axs101";
- compatible = "snps,axs101", "snps,arc-sdp";

4
arch/arc/boot/dts/axs101.dts
View File

@ -13,9 +13,9 @@
/include/ "axs10x_mb.dtsi"
/ {
compatible = "snps,axs101";
compatible = "snps,axs101", "snps,arc-sdp";
chosen {
bootargs = "console=tty0 console=ttyS3,115200n8 consoleblank=0";
bootargs = "earlycon=uart8250,mmio32,0xe0022000,115200n8 console=tty0 console=ttyS3,115200n8 consoleblank=0";
};
};

2
arch/arc/kernel/devtree.c
View File

@ -32,6 +32,8 @@ static void __init arc_set_early_base_baud(unsigned long dt_root)
if (of_flat_dt_is_compatible(dt_root, "abilis,arc-tb10x"))
arc_base_baud = core_clk/3;
else if (of_flat_dt_is_compatible(dt_root, "snps,arc-sdp"))
arc_base_baud = 33333333; /* Fixed 33MHz clk */
else
arc_base_baud = core_clk;
}