Blackfin arch: document why we have to touch the UART peripheral in our boot up code

Signed-off-by: Mike Frysinger <michael.frysinger@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/blackfin/mach-bf533/head.S b/arch/blackfin/mach-bf533/head.S
index 1a54ff5..4db9e62 100644 (file)
--- a/arch/blackfin/mach-bf533/head.S
+++ b/arch/blackfin/mach-bf533/head.S
@@ -173,7 +173,8 @@ ENTRY(__stext)
        STI R2;
 #endif
 
-       /* Initialise UART */
+       /* Initialise UART - when booting from u-boot, the UART is not disabled
+        * so if we dont initalize here, our serial console gets hosed */
        p0.h = hi(UART_LCR);
        p0.l = lo(UART_LCR);
        r0 = 0x0(Z);

diff --git a/arch/blackfin/mach-bf537/head.S b/arch/blackfin/mach-bf537/head.S
index aafc686..b4377dd 100644 (file)
--- a/arch/blackfin/mach-bf537/head.S
+++ b/arch/blackfin/mach-bf537/head.S
@@ -181,7 +181,8 @@ ENTRY(__stext)
        SSYNC;
 #endif
 
-       /*Initialise UART*/
+       /* Initialise UART - when booting from u-boot, the UART is not disabled
+        * so if we dont initalize here, our serial console gets hosed */
        p0.h = hi(UART_LCR);
        p0.l = lo(UART_LCR);
        r0 = 0x0(Z);

diff --git a/arch/blackfin/mach-bf561/head.S b/arch/blackfin/mach-bf561/head.S
index 04f3ac3..9c8e688 100644 (file)
--- a/arch/blackfin/mach-bf561/head.S
+++ b/arch/blackfin/mach-bf561/head.S
@@ -127,7 +127,8 @@ ENTRY(__stext)
        STI R2;
 #endif
 
-       /* Initialise UART*/
+       /* Initialise UART - when booting from u-boot, the UART is not disabled
+        * so if we dont initalize here, our serial console gets hosed */
        p0.h = hi(UART_LCR);
        p0.l = lo(UART_LCR);
        r0 = 0x0(Z);