From 48ef3ca98d92201c36f50ffb5409c38b02e2e953 Mon Sep 17 00:00:00 2001 From: Thomas Gessler Date: Mon, 13 Oct 2014 18:08:47 +0200 Subject: [PATCH] i2c: xiic: Fix big-endian register access The driver tried to access device registers with the (little-endian) iowrite/ioread functions. While this worked on little-endian machines (e.g. Microblaze with AXI bus), it made the driver unusable on big-endian machines (e.g. PPC405 with PLB). During the probe function, the driver tried to write a 32-bit reset mask into the reset register. This caused an error interrupt on big-endian systems, because the device detected an invalid (byte-swapped) reset mask. The result was an Oops. The patch implements an endianness detection similar to the one used in other Xilinx drivers like drivers/spi/spi-xilinx.c. It was tested on a PPC405/PLB system. Signed-off-by: Thomas Gessler Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-xiic.c | 58 ++++++++++++++++++++++++++++++++--- 1 file changed, 53 insertions(+), 5 deletions(-) diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c index cc65ea0b818f..522916a33aa0 100644 --- a/drivers/i2c/busses/i2c-xiic.c +++ b/drivers/i2c/busses/i2c-xiic.c @@ -46,6 +46,11 @@ enum xilinx_i2c_state { STATE_START }; +enum xiic_endian { + LITTLE, + BIG +}; + /** * struct xiic_i2c - Internal representation of the XIIC I2C bus * @base: Memory base of the HW registers @@ -70,6 +75,7 @@ struct xiic_i2c { enum xilinx_i2c_state state; struct i2c_msg *rx_msg; int rx_pos; + enum xiic_endian endianness; }; @@ -170,29 +176,58 @@ struct xiic_i2c { static void xiic_start_xfer(struct xiic_i2c *i2c); static void __xiic_start_xfer(struct xiic_i2c *i2c); +/* + * For the register read and write functions, a little-endian and big-endian + * version are necessary. Endianness is detected during the probe function. + * Only the least significant byte [doublet] of the register are ever + * accessed. This requires an offset of 3 [2] from the base address for + * big-endian systems. + */ + static inline void xiic_setreg8(struct xiic_i2c *i2c, int reg, u8 value) { - iowrite8(value, i2c->base + reg); + if (i2c->endianness == LITTLE) + iowrite8(value, i2c->base + reg); + else + iowrite8(value, i2c->base + reg + 3); } static inline u8 xiic_getreg8(struct xiic_i2c *i2c, int reg) { - return ioread8(i2c->base + reg); + u8 ret; + + if (i2c->endianness == LITTLE) + ret = ioread8(i2c->base + reg); + else + ret = ioread8(i2c->base + reg + 3); + return ret; } static inline void xiic_setreg16(struct xiic_i2c *i2c, int reg, u16 value) { - iowrite16(value, i2c->base + reg); + if (i2c->endianness == LITTLE) + iowrite16(value, i2c->base + reg); + else + iowrite16be(value, i2c->base + reg + 2); } static inline void xiic_setreg32(struct xiic_i2c *i2c, int reg, int value) { - iowrite32(value, i2c->base + reg); + if (i2c->endianness == LITTLE) + iowrite32(value, i2c->base + reg); + else + iowrite32be(value, i2c->base + reg); } static inline int xiic_getreg32(struct xiic_i2c *i2c, int reg) { - return ioread32(i2c->base + reg); + u32 ret; + + if (i2c->endianness == LITTLE) + ret = ioread32(i2c->base + reg); + else + ret = ioread32be(i2c->base + reg); + return ret; } static inline void xiic_irq_dis(struct xiic_i2c *i2c, u32 mask) @@ -692,6 +727,7 @@ static int xiic_i2c_probe(struct platform_device *pdev) struct resource *res; int ret, irq; u8 i; + u32 sr; i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL); if (!i2c) @@ -724,6 +760,18 @@ static int xiic_i2c_probe(struct platform_device *pdev) return ret; } + /* + * Detect endianness + * Try to reset the TX FIFO. Then check the EMPTY flag. If it is not + * set, assume that the endianness was wrong and swap. + */ + i2c->endianness = LITTLE; + xiic_setreg32(i2c, XIIC_CR_REG_OFFSET, XIIC_CR_TX_FIFO_RESET_MASK); + /* Reset is cleared in xiic_reinit */ + sr = xiic_getreg32(i2c, XIIC_SR_REG_OFFSET); + if (!(sr & XIIC_SR_TX_FIFO_EMPTY_MASK)) + i2c->endianness = BIG; + xiic_reinit(i2c); /* add i2c adapter to i2c tree */ -- 2.20.1