[PATCH v3 3/6] gnss: sirf: add support for configurations without wakeup signal
From: Andreas Kemnade
Date: Wed Jan 16 2019 - 16:18:55 EST
Some Wi2Wi devices do not have a wakeup output, so device state can
only be indirectly detected by looking whether there is communitcation
over the serial lines.
This approach requires a report cycle set to a low value to be reliable.
Signed-off-by: Andreas Kemnade <andreas@xxxxxxxxxxxx>
---
Changes in v3:
- was 2/5 earlier
- changed commit headline
- more style cleanup
- split out initial power off as 2/6
- introduced SIRF_REPORT_CYCLE constant
- added documentation about limitations
- ignore first data after power state on so no
shutdown meassages are treated as power on success
- clearer logic in sirf_wait_for_power_state
Changes in v2:
- style cleanup
- do not keep serdev open just because runtime is active,
only when needed (gnss device is opened or state is changed)
- clearer timeout semantics
drivers/gnss/sirf.c | 117 +++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 93 insertions(+), 24 deletions(-)
diff --git a/drivers/gnss/sirf.c b/drivers/gnss/sirf.c
index c7706b91f6f0..943a2ec9b708 100644
--- a/drivers/gnss/sirf.c
+++ b/drivers/gnss/sirf.c
@@ -25,6 +25,16 @@
#define SIRF_ON_OFF_PULSE_TIME 100
#define SIRF_ACTIVATE_TIMEOUT 200
#define SIRF_HIBERNATE_TIMEOUT 200
+/*
+ * If no data arrives for this time, we expect the chip to be off.
+ * REVISIT: The report cycle is configurable and can be several minutes long,
+ * so this will only work reliably if the report cycle is set to a reasonable
+ * low value. Also power saving settings (like send data only on movement)
+ * might things work even worse.
+ * Workaround might be to parse shutdown or bootup messages.
+ * This problem mainly makes error checking uncertain.
+ */
+#define SIRF_REPORT_CYCLE 2000
struct sirf_data {
struct gnss_device *gdev;
@@ -39,9 +49,45 @@ struct sirf_data {
struct mutex gdev_mutex;
bool open;
+ /*
+ * Using the same mutex inside a serdev callback
+ * and around a serdev call leads to lockdep problems.
+ */
+ struct mutex serdev_mutex;
+ int serdev_count;
+
wait_queue_head_t power_wait;
};
+static int sirf_serdev_open(struct sirf_data *data)
+{
+ int ret = 0;
+
+ mutex_lock(&data->serdev_mutex);
+ if (++data->serdev_count == 1) {
+ ret = serdev_device_open(data->serdev);
+ if (ret) {
+ data->serdev_count--;
+ mutex_unlock(&data->serdev_mutex);
+ return ret;
+ }
+
+ serdev_device_set_baudrate(data->serdev, data->speed);
+ serdev_device_set_flow_control(data->serdev, false);
+ }
+ mutex_unlock(&data->serdev_mutex);
+
+ return ret;
+}
+
+static void sirf_serdev_close(struct sirf_data *data)
+{
+ mutex_lock(&data->serdev_mutex);
+ if (--data->serdev_count == 0)
+ serdev_device_close(data->serdev);
+ mutex_unlock(&data->serdev_mutex);
+}
+
static int sirf_open(struct gnss_device *gdev)
{
struct sirf_data *data = gnss_get_drvdata(gdev);
@@ -52,7 +98,7 @@ static int sirf_open(struct gnss_device *gdev)
data->open = true;
mutex_unlock(&data->gdev_mutex);
- ret = serdev_device_open(serdev);
+ ret = sirf_serdev_open(data);
if (ret) {
mutex_lock(&data->gdev_mutex);
data->open = false;
@@ -60,10 +106,6 @@ static int sirf_open(struct gnss_device *gdev)
return ret;
}
-
- serdev_device_set_baudrate(serdev, data->speed);
- serdev_device_set_flow_control(serdev, false);
-
ret = pm_runtime_get_sync(&serdev->dev);
if (ret < 0) {
dev_err(&gdev->dev, "failed to runtime resume: %d\n", ret);
@@ -74,7 +116,7 @@ static int sirf_open(struct gnss_device *gdev)
return 0;
err_close:
- serdev_device_close(serdev);
+ sirf_serdev_close(data);
mutex_lock(&data->gdev_mutex);
data->open = false;
@@ -88,7 +130,7 @@ static void sirf_close(struct gnss_device *gdev)
struct sirf_data *data = gnss_get_drvdata(gdev);
struct serdev_device *serdev = data->serdev;
- serdev_device_close(serdev);
+ sirf_serdev_close(data);
pm_runtime_put(&serdev->dev);
@@ -128,6 +170,11 @@ static int sirf_receive_buf(struct serdev_device *serdev,
struct gnss_device *gdev = data->gdev;
int ret = 0;
+ if (!data->wakeup && !data->active) {
+ data->active = true;
+ wake_up_interruptible(&data->power_wait);
+ }
+
mutex_lock(&data->gdev_mutex);
if (data->open)
ret = gnss_insert_raw(gdev, buf, count);
@@ -163,6 +210,24 @@ static int sirf_wait_for_power_state(struct sirf_data *data, bool active,
{
int ret;
+ if (!data->wakeup) {
+ /* Wait for boot or shutdown messages */
+ msleep(timeout);
+ data->active = false;
+ /* Now check if it is really off. */
+ ret = wait_event_interruptible_timeout(data->power_wait,
+ data->active,
+ msecs_to_jiffies(SIRF_REPORT_CYCLE));
+ if (ret < 0)
+ return ret;
+
+ if ((ret > 0 && !active) ||
+ (ret == 0 && active))
+ return -ETIMEDOUT;
+
+ return 0;
+ }
+
ret = wait_event_interruptible_timeout(data->power_wait,
data->active == active, msecs_to_jiffies(timeout));
if (ret < 0)
@@ -195,18 +260,29 @@ static int sirf_set_active(struct sirf_data *data, bool active)
else
timeout = SIRF_HIBERNATE_TIMEOUT;
+ if (!data->wakeup) {
+ ret = sirf_serdev_open(data);
+ if (ret)
+ return ret;
+ }
+
do {
- sirf_pulse_on_off(data);
+ /*
+ * Try to avoid unneeded, time-consuming state toggles
+ * in the configurations without wakeup signal. This counts
+ * especially for the initial off state check.
+ */
+ if (data->wakeup || data->active || active)
+ sirf_pulse_on_off(data);
+
ret = sirf_wait_for_power_state(data, active, timeout);
- if (ret < 0) {
- if (ret == -ETIMEDOUT)
- continue;
+ } while (ret == -ETIMEDOUT && retries--);
- return ret;
- }
+ if (!data->wakeup)
+ sirf_serdev_close(data);
- break;
- } while (retries--);
+ if (ret)
+ return ret;
if (retries < 0)
return -ETIMEDOUT;
@@ -303,6 +379,7 @@ static int sirf_probe(struct serdev_device *serdev)
data->gdev = gdev;
mutex_init(&data->gdev_mutex);
+ mutex_init(&data->serdev_mutex);
init_waitqueue_head(&data->power_wait);
serdev_device_set_drvdata(serdev, data);
@@ -329,15 +406,6 @@ static int sirf_probe(struct serdev_device *serdev)
if (IS_ERR(data->wakeup))
goto err_put_device;
- /*
- * Configurations where WAKEUP has been left not connected,
- * are currently not supported.
- */
- if (!data->wakeup) {
- dev_err(dev, "no wakeup gpio specified\n");
- ret = -ENODEV;
- goto err_put_device;
- }
}
if (data->wakeup) {
@@ -421,6 +489,7 @@ static void sirf_remove(struct serdev_device *serdev)
static const struct of_device_id sirf_of_match[] = {
{ .compatible = "fastrax,uc430" },
{ .compatible = "linx,r4" },
+ { .compatible = "wi2wi,w2sg0004" },
{ .compatible = "wi2wi,w2sg0008i" },
{ .compatible = "wi2wi,w2sg0084i" },
{},
--
2.11.0