From 7e31cea7d1e0f4b683dc45c21530cd3ee82559b4 Mon Sep 17 00:00:00 2001 From: Serge Semin Date: Sun, 20 Sep 2020 14:28:51 +0300 Subject: [PATCH] spi: dw: Use relaxed IO-methods to access FIFOs In accordance with [1] the relaxed methods are guaranteed to be ordered with respect to other accesses from the same CPU thread to the same peripheral. This is what we need during the data read/write from/to the controller FIFOs being executed within a single IRQ handler or a kernel task. Such optimization shall significantly speed the data reader and writer up. For instance, the relaxed IO-accessors utilization on Baikal-T1 lets the driver to support the SPI memory operations with bus frequency three-fold faster than if normal IO-accessors would be used. [1] "LINUX KERNEL MEMORY BARRIERS", Documentation/memory-barriers.txt, Section "KERNEL I/O BARRIER EFFECTS" Signed-off-by: Serge Semin Link: https://lore.kernel.org/r/20200920112914.26501-8-Sergey.Semin@baikalelectronics.ru Signed-off-by: Mark Brown --- drivers/spi/spi-dw.h | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h index 6b30f5089218..40b2c8c0c2a2 100644 --- a/drivers/spi/spi-dw.h +++ b/drivers/spi/spi-dw.h @@ -162,29 +162,19 @@ static inline u32 dw_readl(struct dw_spi *dws, u32 offset) return __raw_readl(dws->regs + offset); } -static inline u16 dw_readw(struct dw_spi *dws, u32 offset) -{ - return __raw_readw(dws->regs + offset); -} - static inline void dw_writel(struct dw_spi *dws, u32 offset, u32 val) { __raw_writel(val, dws->regs + offset); } -static inline void dw_writew(struct dw_spi *dws, u32 offset, u16 val) -{ - __raw_writew(val, dws->regs + offset); -} - static inline u32 dw_read_io_reg(struct dw_spi *dws, u32 offset) { switch (dws->reg_io_width) { case 2: - return dw_readw(dws, offset); + return readw_relaxed(dws->regs + offset); case 4: default: - return dw_readl(dws, offset); + return readl_relaxed(dws->regs + offset); } } @@ -192,11 +182,11 @@ static inline void dw_write_io_reg(struct dw_spi *dws, u32 offset, u32 val) { switch (dws->reg_io_width) { case 2: - dw_writew(dws, offset, val); + writew_relaxed(val, dws->regs + offset); break; case 4: default: - dw_writel(dws, offset, val); + writel_relaxed(val, dws->regs + offset); break; } }