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authorMarek Vasut <marex@denx.de>2013-11-04 14:29:12 +0100
committerHeiko Schocher <hs@denx.de>2013-11-13 06:08:31 +0100
commit124913556c4b99909f40b4bf4ceaefe2b555d6f8 (patch)
treedb5e072f22de6055075a620e21004ced7026e096 /drivers/i2c
parent2035d77d790044f389a18c0e6baa05e86d4b32a0 (diff)
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i2c: mxs_i2c: Squash endless loop
The endless waiting for a bit to be set can cause a hang, add a timeout so we prevent such situation. A testcase for such a hang is below. The testcase assumes a device to be present at address 0x50 and a device to NOT be present at address 0x42 . Also note that the "sleep 1" induced delays are imperative for this bug to manifest . i2c read 0x42 0x0.2 0x10 0x42000000 ; sleep 1 ; \ i2c read 0x50 0x0.2 0x10 0x42000000 ; sleep 1 ; \ i2c read 0x42 0x0.2 0x10 0x42000000 The expected result of the above command is: Error reading the chip. Error reading the chip. While without this patch, we observe a hang in the last read from 0x42 precisely when waiting for this bit to be set. Signed-off-by: Marek Vasut <marex@denx.de> Cc: Fabio Estevam <fabio.estevam@freescale.com> Cc: Heiko Schocher <hs@denx.de> Cc: Stefano Babic <sbabic@denx.de>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/mxs_i2c.c15
1 files changed, 12 insertions, 3 deletions
diff --git a/drivers/i2c/mxs_i2c.c b/drivers/i2c/mxs_i2c.c
index 46106b7..a298c95 100644
--- a/drivers/i2c/mxs_i2c.c
+++ b/drivers/i2c/mxs_i2c.c
@@ -150,6 +150,7 @@ int i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
{
struct mxs_i2c_regs *i2c_regs = (struct mxs_i2c_regs *)MXS_I2C0_BASE;
uint32_t tmp = 0;
+ int timeout = MXS_I2C_MAX_TIMEOUT;
int ret;
int i;
@@ -169,9 +170,17 @@ int i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
for (i = 0; i < len; i++) {
if (!(i & 3)) {
- while (readl(&i2c_regs->hw_i2c_queuestat) &
- I2C_QUEUESTAT_RD_QUEUE_EMPTY)
- ;
+ while (--timeout) {
+ tmp = readl(&i2c_regs->hw_i2c_queuestat);
+ if (!(tmp & I2C_QUEUESTAT_RD_QUEUE_EMPTY))
+ break;
+ }
+
+ if (!timeout) {
+ debug("MXS I2C: Failed receiving data!\n");
+ return -ETIMEDOUT;
+ }
+
tmp = readl(&i2c_regs->hw_i2c_queuedata);
}
buffer[i] = tmp & 0xff;