From: Stephen Boyd Date: Thu, 3 Feb 2011 23:48:36 +0000 (-0800) Subject: hvc_dcc: Simplify assembly for v6 and v7 ARM X-Git-Tag: v2.6.39-rc1~470^2~63 X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=8e6d3fe1af38bea3f6c003f8737d2e3a02d00fa0;p=~shefty%2Frdma-dev.git hvc_dcc: Simplify assembly for v6 and v7 ARM The inline assembly differences for v6 vs. v7 in the hvc_dcc driver are purely optimizations. On a v7 processor, an mrc with the pc sets the condition codes to the 28-31 bits of the register being read. It just so happens that the TX/RX full bits the DCC driver is testing for are high enough in the register to be put into the condition codes. On a v6 processor, this "feature" isn't implemented and thus we have to do the usual read, mask, test operations to check for TX/RX full. Since we already test the RX/TX full bits before calling __dcc_getchar() and __dcc_putchar() we don't actually need to do anything special for v7 over v6. The only difference is in hvc_dcc_get_chars(). We would test RX full, poll RX full, and then read a character from the buffer, whereas now we will test RX full, read a character from the buffer, and then test RX full again for the second iteration of the loop. It doesn't seem possible for the buffer to go from full to empty between testing the RX full and reading a character. Therefore, replace the v7 versions with the v6 versions and everything works the same. Acked-by: Tony Lindgren Cc: Arnd Bergmann Acked-by: Nicolas Pitre Cc: Daniel Walker Signed-off-by: Stephen Boyd Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/hvc/hvc_dcc.c b/drivers/tty/hvc/hvc_dcc.c index ad23cc8082a..435f6facbc2 100644 --- a/drivers/tty/hvc/hvc_dcc.c +++ b/drivers/tty/hvc/hvc_dcc.c @@ -40,19 +40,6 @@ static inline u32 __dcc_getstatus(void) } -#if defined(CONFIG_CPU_V7) -static inline char __dcc_getchar(void) -{ - char __c; - - asm volatile("get_wait: mrc p14, 0, pc, c0, c1, 0 \n\ - bne get_wait \n\ - mrc p14, 0, %0, c0, c5, 0 @ read comms data reg" - : "=r" (__c) : : "cc"); - - return __c; -} -#else static inline char __dcc_getchar(void) { char __c; @@ -62,24 +49,13 @@ static inline char __dcc_getchar(void) return __c; } -#endif -#if defined(CONFIG_CPU_V7) -static inline void __dcc_putchar(char c) -{ - asm volatile("put_wait: mrc p14, 0, pc, c0, c1, 0 \n\ - bcs put_wait \n\ - mcr p14, 0, %0, c0, c5, 0 " - : : "r" (c) : "cc"); -} -#else static inline void __dcc_putchar(char c) { asm volatile("mcr p14, 0, %0, c0, c5, 0 @ write a char" : /* no output register */ : "r" (c)); } -#endif static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count) {