[PATCH 12/12] tty: amba-pl011: switch to using relaxed IO accessors
From: Russell King <hidden>
Date: 2015-11-16 17:41:02
Also in:
linux-serial
Subsystem:
arm primecell uart pl010 and pl011 drivers, the rest, tty layer and serial drivers · Maintainers:
Russell King, Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
Using relaxed IO accessors allows GCC to better optimise this code as we eliminate the heavy memory barriers - for example, GCC can now cache the address of a register across a read-modify-write sequence, rather than reloading the base address, offset and access size flag. Signed-off-by: Russell King <redacted> --- drivers/tty/serial/amba-pl011.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 54c6c88a71a3..a7d7ab05dc64 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c@@ -262,7 +262,7 @@ static unsigned int pl011_read(const struct uart_amba_port *uap, { void __iomem *addr = uap->port.membase + pl011_reg_to_offset(uap, reg); - return uap->access_32b ? readl(addr) : readw(addr); + return uap->access_32b ? readl_relaxed(addr) : readw_relaxed(addr); } static void pl011_write(unsigned int val, const struct uart_amba_port *uap,
@@ -271,9 +271,9 @@ static void pl011_write(unsigned int val, const struct uart_amba_port *uap, void __iomem *addr = uap->port.membase + pl011_reg_to_offset(uap, reg); if (uap->access_32b) - writel(val, addr); + writel_relaxed(val, addr); else - writew(val, addr); + writew_relaxed(val, addr); } /*
--
2.1.0