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Message-Id: <1413216527-11933-1-git-send-email-Thomas.Gessler@exp2.physik.uni-giessen.de>
Date: Mon, 13 Oct 2014 18:08:47 +0200
From: Thomas Gessler <Thomas.Gessler@...2.physik.uni-giessen.de>
To: wsa@...-dreams.de
Cc: michal.simek@...inx.com, appana.durga.rao@...inx.com,
khali@...ux-fr.org, sachin.kamat@...aro.org,
paul.gortmaker@...driver.com,
Thomas.Gessler@...2.physik.uni-giessen.de,
linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] i2c: 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 <Thomas.Gessler@...2.physik.uni-giessen.de>
---
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 ade9223..9842660 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -50,6 +50,11 @@ 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
@@ -74,6 +79,7 @@ struct xiic_i2c {
enum xilinx_i2c_state state;
struct i2c_msg *rx_msg;
int rx_pos;
+ enum xiic_endian endianness;
};
@@ -174,29 +180,58 @@ 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)
@@ -696,6 +731,7 @@ 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)
@@ -728,6 +764,18 @@ 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 */
--
2.1.2
--
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