[PATCH v2 4/6] i2c: xiic: Switch from waitqueue to completion

Marek Vasut
2021-08-23T21:42:20Z

There will never be threads queueing up in the xiic_xmit(), use
completion synchronization primitive to wait for the interrupt
handler thread to complete instead as it is much better fit and
there is no need to overload it for this purpose.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Cc: Wolfram Sang <wsa@kernel.org>
---
V2: Add separate timeout for the transfer completion, since on SMP zynqmp
it can happen that the interrupt handler thread is preempted for longer
than a second (measurements indicate below 2 seconds most of the time).
So add a separate timeout and make it long to give this a chance.
---
drivers/i2c/busses/i2c-xiic.c | 33 ++++++++++++++++++---------------
1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index aecdeec579977..f7277629923ff 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -23,7 +23,7 @@
#include <linux/platform_device.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
-#include <linux/wait.h>
+#include <linux/completion.h>
#include <linux/platform_data/i2c-xiic.h>
#include <linux/io.h>
#include <linux/slab.h>
@@ -48,7 +48,7 @@ enum xiic_endian {
* struct xiic_i2c - Internal representation of the XIIC I2C bus
* @dev: Pointer to device structure
* @base: Memory base of the HW registers
- * @wait: Wait queue for callers
+ * @completion: Completion for callers
* @adap: Kernel adapter representation
* @tx_msg: Messages from above to be sent
* @lock: Mutual exclusion
@@ -64,7 +64,7 @@ enum xiic_endian {
struct xiic_i2c {
struct device *dev;
void __iomem *base;
- wait_queue_head_t wait;
+ struct completion completion;
struct i2c_adapter adap;
struct i2c_msg *tx_msg;
struct mutex lock;
@@ -160,6 +160,9 @@ struct xiic_i2c {
#define XIIC_PM_TIMEOUT 1000 /* ms */
/* timeout waiting for the controller to respond */
#define XIIC_I2C_TIMEOUT (msecs_to_jiffies(1000))
+/* timeout waiting for the controller finish transfers */
+#define XIIC_XFER_TIMEOUT (msecs_to_jiffies(10000))
+
/*
* The following constant is used for the device global interrupt enable
* register, to enable all interrupts for the device, this is the only bit
@@ -367,7 +370,7 @@ static void xiic_wakeup(struct xiic_i2c *i2c, int code)
i2c->rx_msg = NULL;
i2c->nmsgs = 0;
i2c->state = code;
- wake_up(&i2c->wait);
+ complete(&i2c->completion);
}

static irqreturn_t xiic_process(int irq, void *dev_id)
@@ -689,6 +692,7 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
i2c->tx_msg = msgs;
i2c->rx_msg = NULL;
i2c->nmsgs = num;
+ init_completion(&i2c->completion);

ret = xiic_reinit(i2c);
if (!ret)
@@ -715,23 +719,23 @@ static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
err = xiic_start_xfer(i2c, msgs, num);
if (err < 0) {
dev_err(adap->dev.parent, "Error xiic_start_xfer\n");
- goto out;
+ return err;
}

- if (wait_event_timeout(i2c->wait, (i2c->state == STATE_ERROR) ||
- (i2c->state == STATE_DONE), HZ)) {
- mutex_lock(&i2c->lock);
- err = (i2c->state == STATE_DONE) ? num : -EIO;
- goto out;
- } else {
- mutex_lock(&i2c->lock);
+ err = wait_for_completion_timeout(&i2c->completion, XIIC_XFER_TIMEOUT);
+ mutex_lock(&i2c->lock);
+ if (err == 0) { /* Timeout */
i2c->tx_msg = NULL;
i2c->rx_msg = NULL;
i2c->nmsgs = 0;
err = -ETIMEDOUT;
- goto out;
+ } else if (err < 0) { /* Completion error */
+ i2c->tx_msg = NULL;
+ i2c->rx_msg = NULL;
+ i2c->nmsgs = 0;
+ } else {
+ err = (i2c->state == STATE_DONE) ? num : -EIO;
}
-out:
mutex_unlock(&i2c->lock);
pm_runtime_mark_last_busy(i2c->dev);
pm_runtime_put_autosuspend(i2c->dev);
@@ -793,7 +797,6 @@ static int xiic_i2c_probe(struct platform_device *pdev)
i2c->adap.dev.of_node = pdev->dev.of_node;

mutex_init(&i2c->lock);
- init_waitqueue_head(&i2c->wait);

i2c->clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(i2c->clk))
--
2.32.0