All of lore.kernel.org
 help / color / mirror / Atom feed
* [PATCH v2] i2c-eg20t: Rework pch_i2c_wait_for_bus_idle to reduce wait time
@ 2012-02-20  8:14 ` Alexander Stein
  0 siblings, 0 replies; 14+ messages in thread
From: Alexander Stein @ 2012-02-20  8:14 UTC (permalink / raw)
  To: Jean Delvare, Ben Dooks, Wolfram Sang
  Cc: Tomoya MORINAGA, Feng Tang, Toshiharu Okada,
	linux-i2c-u79uwXL29TY76Z2rM5mHXA,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA, Alexander Stein

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 <alexander.stein-93q1YBGzJSMe9JSWTWOYM3xStJ4P+DSV@public.gmane.org>
---
Changes in v2:
* Remove redundant code

 drivers/i2c/busses/i2c-eg20t.c |   42 ++++++++++++++++++++++-----------------
 1 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/drivers/i2c/busses/i2c-eg20t.c b/drivers/i2c/busses/i2c-eg20t.c
index ca88776..1eb60ca 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;
 }
 
 /**
-- 
1.7.3.4

^ permalink raw reply related	[flat|nested] 14+ messages in thread
end of thread, other threads:[~2012-03-07 18:16 UTC | newest]

Thread overview: 14+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2012-02-20  8:14 [PATCH v2] i2c-eg20t: Rework pch_i2c_wait_for_bus_idle to reduce wait time Alexander Stein
2012-02-20  8:14 ` Alexander Stein
     [not found] ` <1329725656-32715-1-git-send-email-alexander.stein-93q1YBGzJSMe9JSWTWOYM3xStJ4P+DSV@public.gmane.org>
2012-02-24 12:17   ` Wolfram Sang
2012-02-24 12:17     ` Wolfram Sang
     [not found]     ` <20120224121753.GE2479-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-02-27 23:53       ` Tomoya MORINAGA
2012-02-27 23:53         ` Tomoya MORINAGA
     [not found]         ` <CANKRQngWB8kUO68UdbDeWey5eGRF0nGCE341j8jyCMogvYUYKA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-03-01 10:15           ` Wolfram Sang
2012-03-01 10:15             ` Wolfram Sang
     [not found]             ` <20120301101502.GB2535-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-03-02  0:51               ` Tomoya MORINAGA
2012-03-02  0:51                 ` Tomoya MORINAGA
     [not found]                 ` <CANKRQniA2icHddFG22r7VtLTuoefbK61tpcUQnXgShFHuffUuA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-03-06  7:36                   ` Alexander Stein
2012-03-06  7:36                     ` Alexander Stein
2012-03-07 18:16                     ` Wolfram Sang
2012-03-07 18:16                       ` Wolfram Sang

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.