From: Stephen Boyd <sboyd@codeaurora.org> To: Greg Kroah-Hartman <gregkh@suse.de> Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Tony Lindgren <tony@atomide.com>, Arnd Bergmann <arnd@arndb.de>, Nicolas Pitre <nicolas.pitre@linaro.org>, Daniel Walker <dwalker@codeaurora.org> Subject: [PATCH] hvc_dcc: Simplify assembly for v6 and v7 ARM Date: Fri, 17 Dec 2010 21:16:25 -0800 [thread overview] Message-ID: <1292649385-28771-1-git-send-email-sboyd@codeaurora.org> (raw) In-Reply-To: <20101201192856.GA731@suse.de> 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. While we're here, cleanup the for loops a bit and mark the inline assembly as volatile. Not marking it volatile causes GCC to cache the results of the status and RX buffer registers causing lockups. Cc: Tony Lindgren <tony@atomide.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Nicolas Pitre <nicolas.pitre@linaro.org> Cc: Daniel Walker <dwalker@codeaurora.org> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> --- drivers/char/hvc_dcc.c | 43 +++++++------------------------------------ 1 files changed, 7 insertions(+), 36 deletions(-) diff --git a/drivers/char/hvc_dcc.c b/drivers/char/hvc_dcc.c index 6470f63..435f6fa 100644 --- a/drivers/char/hvc_dcc.c +++ b/drivers/char/hvc_dcc.c @@ -33,54 +33,29 @@ static inline u32 __dcc_getstatus(void) { u32 __ret; - - asm("mrc p14, 0, %0, c0, c1, 0 @ read comms ctrl reg" + asm volatile("mrc p14, 0, %0, c0, c1, 0 @ read comms ctrl reg" : "=r" (__ret) : : "cc"); return __ret; } -#if defined(CONFIG_CPU_V7) static inline char __dcc_getchar(void) { char __c; - asm("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; - - asm("mrc p14, 0, %0, c0, c5, 0 @ read comms data reg" + asm volatile("mrc p14, 0, %0, c0, c5, 0 @ read comms data reg" : "=r" (__c)); return __c; } -#endif -#if defined(CONFIG_CPU_V7) -static inline void __dcc_putchar(char c) -{ - asm("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("mcr p14, 0, %0, c0, c5, 0 @ write a char" + 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) { @@ -90,7 +65,7 @@ static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count) while (__dcc_getstatus() & DCC_STATUS_TX) cpu_relax(); - __dcc_putchar((char)(buf[i] & 0xFF)); + __dcc_putchar(buf[i]); } return count; @@ -100,15 +75,11 @@ static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count) { int i; - for (i = 0; i < count; ++i) { - int c = -1; - + for (i = 0; i < count; ++i) if (__dcc_getstatus() & DCC_STATUS_RX) - c = __dcc_getchar(); - if (c < 0) + buf[i] = __dcc_getchar(); + else break; - buf[i] = c; - } return i; } -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
WARNING: multiple messages have this Message-ID (diff)
From: sboyd@codeaurora.org (Stephen Boyd) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH] hvc_dcc: Simplify assembly for v6 and v7 ARM Date: Fri, 17 Dec 2010 21:16:25 -0800 [thread overview] Message-ID: <1292649385-28771-1-git-send-email-sboyd@codeaurora.org> (raw) In-Reply-To: <20101201192856.GA731@suse.de> 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. While we're here, cleanup the for loops a bit and mark the inline assembly as volatile. Not marking it volatile causes GCC to cache the results of the status and RX buffer registers causing lockups. Cc: Tony Lindgren <tony@atomide.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Nicolas Pitre <nicolas.pitre@linaro.org> Cc: Daniel Walker <dwalker@codeaurora.org> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> --- drivers/char/hvc_dcc.c | 43 +++++++------------------------------------ 1 files changed, 7 insertions(+), 36 deletions(-) diff --git a/drivers/char/hvc_dcc.c b/drivers/char/hvc_dcc.c index 6470f63..435f6fa 100644 --- a/drivers/char/hvc_dcc.c +++ b/drivers/char/hvc_dcc.c @@ -33,54 +33,29 @@ static inline u32 __dcc_getstatus(void) { u32 __ret; - - asm("mrc p14, 0, %0, c0, c1, 0 @ read comms ctrl reg" + asm volatile("mrc p14, 0, %0, c0, c1, 0 @ read comms ctrl reg" : "=r" (__ret) : : "cc"); return __ret; } -#if defined(CONFIG_CPU_V7) static inline char __dcc_getchar(void) { char __c; - asm("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; - - asm("mrc p14, 0, %0, c0, c5, 0 @ read comms data reg" + asm volatile("mrc p14, 0, %0, c0, c5, 0 @ read comms data reg" : "=r" (__c)); return __c; } -#endif -#if defined(CONFIG_CPU_V7) -static inline void __dcc_putchar(char c) -{ - asm("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("mcr p14, 0, %0, c0, c5, 0 @ write a char" + 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) { @@ -90,7 +65,7 @@ static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count) while (__dcc_getstatus() & DCC_STATUS_TX) cpu_relax(); - __dcc_putchar((char)(buf[i] & 0xFF)); + __dcc_putchar(buf[i]); } return count; @@ -100,15 +75,11 @@ static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count) { int i; - for (i = 0; i < count; ++i) { - int c = -1; - + for (i = 0; i < count; ++i) if (__dcc_getstatus() & DCC_STATUS_RX) - c = __dcc_getchar(); - if (c < 0) + buf[i] = __dcc_getchar(); + else break; - buf[i] = c; - } return i; } -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
next prev parent reply other threads:[~2010-12-18 5:16 UTC|newest] Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top 2010-11-30 19:25 [PATCH] drivers: char: hvc: add arm JTAG DCC console support Daniel Walker 2010-11-30 19:25 ` Daniel Walker 2010-11-30 19:57 ` Nicolas Pitre 2010-11-30 19:57 ` Nicolas Pitre 2010-11-30 21:17 ` Arnd Bergmann 2010-11-30 21:17 ` Arnd Bergmann 2010-12-01 5:30 ` Stephen Boyd 2010-12-01 5:30 ` Stephen Boyd 2010-12-01 18:54 ` Daniel Walker 2010-12-01 18:54 ` Daniel Walker 2010-12-01 19:28 ` Greg KH 2010-12-01 19:28 ` Greg KH 2010-12-18 5:16 ` Stephen Boyd [this message] 2010-12-18 5:16 ` [PATCH] hvc_dcc: Simplify assembly for v6 and v7 ARM Stephen Boyd 2010-12-20 17:51 ` Daniel Walker 2010-12-20 17:51 ` Daniel Walker 2010-12-20 18:39 ` Stephen Boyd 2010-12-20 18:39 ` Stephen Boyd 2010-12-20 18:46 ` Nicolas Pitre 2010-12-20 18:46 ` Nicolas Pitre 2010-12-20 20:08 ` [PATCH 0/3] hvc_dcc cleanups and fixes Stephen Boyd 2010-12-20 20:08 ` Stephen Boyd 2010-12-20 20:08 ` [PATCH 1/3] hvc_dcc: Fix bad code generation by marking assembly volatile Stephen Boyd 2010-12-20 20:08 ` Stephen Boyd 2010-12-20 21:39 ` Nicolas Pitre 2010-12-20 21:39 ` Nicolas Pitre 2011-01-02 9:00 ` Pavel Machek 2011-01-02 9:00 ` Pavel Machek 2011-01-02 18:49 ` David Brown 2011-01-02 18:49 ` David Brown 2011-01-03 5:50 ` Pavel Machek 2011-01-03 5:50 ` Pavel Machek 2011-01-04 18:49 ` Tony Lindgren 2011-01-04 18:49 ` Tony Lindgren 2010-12-20 21:49 ` Arnaud Lacombe 2010-12-20 21:49 ` Arnaud Lacombe 2010-12-20 21:52 ` Stephen Boyd 2010-12-20 21:52 ` Stephen Boyd 2010-12-20 22:10 ` Nicolas Pitre 2010-12-20 22:10 ` Nicolas Pitre 2010-12-20 20:08 ` [PATCH 2/3] hvc_dcc: Simplify put_chars()/get_chars() loops Stephen Boyd 2010-12-20 20:08 ` Stephen Boyd 2010-12-20 20:08 ` [PATCH 3/3] hvc_dcc: Simplify assembly for v6 and v7 ARM Stephen Boyd 2010-12-20 20:08 ` Stephen Boyd 2010-12-20 21:44 ` Nicolas Pitre 2010-12-20 21:44 ` Nicolas Pitre 2011-01-04 18:52 ` Tony Lindgren 2011-01-04 18:52 ` Tony Lindgren 2011-01-06 1:49 ` [PATCH 0/3] hvc_dcc cleanups and fixes Stephen Boyd 2011-01-06 1:49 ` Stephen Boyd 2011-01-06 3:20 ` Greg KH 2011-01-06 3:20 ` Greg KH 2011-02-03 22:17 ` Greg KH 2011-02-03 22:17 ` Greg KH 2011-02-03 22:17 ` Greg KH 2011-02-03 23:19 ` Stephen Boyd 2011-02-03 23:19 ` Stephen Boyd 2011-02-03 23:30 ` Greg KH 2011-02-03 23:30 ` Greg KH 2011-02-03 23:48 ` [PATCHv2 " Stephen Boyd 2011-02-03 23:48 ` Stephen Boyd 2011-02-03 23:48 ` [PATCHv2 1/3] hvc_dcc: Fix bad code generation by marking assembly volatile Stephen Boyd 2011-02-03 23:48 ` Stephen Boyd 2011-02-03 23:48 ` [PATCHv2 2/3] hvc_dcc: Simplify put_chars()/get_chars() loops Stephen Boyd 2011-02-03 23:48 ` Stephen Boyd 2011-02-03 23:48 ` [PATCHv2 3/3] hvc_dcc: Simplify assembly for v6 and v7 ARM Stephen Boyd 2011-02-03 23:48 ` Stephen Boyd 2010-12-01 20:20 ` [PATCH] drivers: char: hvc: add arm JTAG DCC console support Stephen Boyd 2010-12-01 20:20 ` Stephen Boyd 2010-12-07 19:10 ` Stephen Boyd 2010-12-07 19:10 ` Stephen Boyd 2011-01-14 19:19 ` Tony Lindgren 2011-01-14 19:19 ` Tony Lindgren 2011-01-14 23:49 ` Stephen Boyd 2011-01-14 23:49 ` Stephen Boyd 2011-04-07 18:39 ` RONETIX - Asen Dimov 2011-04-07 18:39 ` RONETIX - Asen Dimov 2011-04-07 18:57 ` Mike Frysinger 2011-04-07 18:57 ` Mike Frysinger
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