From 0836c80901565e8549e17cbad6933ab7e48ef6b2 Mon Sep 17 00:00:00 2001 From: Alexander Stein Date: Mon, 20 Feb 2012 09:14:16 +0100 Subject: i2c-eg20t: Rework pch_i2c_wait_for_bus_idle to reduce wait time If you insert several i2c transfers, the driver might start the next one while the STOP bit of the previous transfer is still on the bus, marking the bus as busy. pch_i2c_wait_for_bus_idle does an msleep(20) delaying the next transfer by >=20ms. Reduce wait time by actively waiting 5 us once, then using usleep_range. Signed-off-by: Alexander Stein Acked-by: Tomoya MORINAGA Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-eg20t.c | 36 +++++++++++++++++++++--------------- 1 file changed, 21 insertions(+), 15 deletions(-) (limited to 'drivers/i2c') diff --git a/drivers/i2c/busses/i2c-eg20t.c b/drivers/i2c/busses/i2c-eg20t.c index ca887764104..1eb60ca055a 100644 --- a/drivers/i2c/busses/i2c-eg20t.c +++ b/drivers/i2c/busses/i2c-eg20t.c @@ -271,30 +271,36 @@ static inline bool ktime_lt(const ktime_t cmp1, const ktime_t cmp2) /** * pch_i2c_wait_for_bus_idle() - check the status of bus. * @adap: Pointer to struct i2c_algo_pch_data. - * @timeout: waiting time counter (us). + * @timeout: waiting time counter (ms). */ static s32 pch_i2c_wait_for_bus_idle(struct i2c_algo_pch_data *adap, s32 timeout) { void __iomem *p = adap->pch_base_address; - ktime_t ns_val; + int schedule = 0; + unsigned long end = jiffies + msecs_to_jiffies(timeout); + + while (ioread32(p + PCH_I2CSR) & I2CMBB_BIT) { + if (time_after(jiffies, end)) { + pch_dbg(adap, "I2CSR = %x\n", ioread32(p + PCH_I2CSR)); + pch_err(adap, "%s: Timeout Error.return%d\n", + __func__, -ETIME); + pch_i2c_init(adap); - if ((ioread32(p + PCH_I2CSR) & I2CMBB_BIT) == 0) - return 0; + return -ETIME; + } - /* MAX timeout value is timeout*1000*1000nsec */ - ns_val = ktime_add_ns(ktime_get(), timeout*1000*1000); - do { - msleep(20); - if ((ioread32(p + PCH_I2CSR) & I2CMBB_BIT) == 0) - return 0; - } while (ktime_lt(ktime_get(), ns_val)); + if (!schedule) + /* Retry after some usecs */ + udelay(5); + else + /* Wait a bit more without consuming CPU */ + usleep_range(20, 1000); - pch_dbg(adap, "I2CSR = %x\n", ioread32(p + PCH_I2CSR)); - pch_err(adap, "%s: Timeout Error.return%d\n", __func__, -ETIME); - pch_i2c_init(adap); + schedule = 1; + } - return -ETIME; + return 0; } /** -- cgit v1.2.3