This is a note to let you know that I've just added the patch titled
ice: do not busy-wait to read GNSS data
to the 6.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ice-do-not-busy-wait-to-read-gnss-data.patch
and it can be found in the queue-6.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit abc213afc1e7fd49c6b14d3a916b5221c4285e56
Author: Michal Schmidt <mschmidt@xxxxxxxxxx>
Date: Wed Apr 12 10:19:24 2023 +0200
ice: do not busy-wait to read GNSS data
[ Upstream commit 2f8fdcb0a73a1831cc4f205f23493a17c0e5536f ]
The ice-gnss-<dev_name> kernel thread, which reads data from the u-blox
GNSS module, keep a CPU core almost 100% busy. The main reason is that
it busy-waits for data to become available.
A simple improvement would be to replace the "mdelay(10);" in
ice_gnss_read() with sleeping. A better fix is to not do any waiting
directly in the function and just requeue this delayed work as needed.
The advantage is that canceling the work from ice_gnss_exit() becomes
immediate, rather than taking up to ~2.5 seconds (ICE_MAX_UBX_READ_TRIES
* 10 ms).
This lowers the CPU usage of the ice-gnss-<dev_name> thread on my system
from ~90 % to ~8 %.
I am not sure if the larger 0.1 s pause after inserting data into the
gnss subsystem is really necessary, but I'm keeping that as it was.
Of course, ideally the driver would not have to poll at all, but I don't
know if the E810 can watch for GNSS data availability over the i2c bus
by itself and notify the driver.
Signed-off-by: Michal Schmidt <mschmidt@xxxxxxxxxx>
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@xxxxxxxxx>
Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
Tested-by: Sunitha Mekala <sunithax.d.mekala@xxxxxxxxx> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@xxxxxxxxx>
Stable-dep-of: 05a1308a2e08 ("ice: Don't dereference NULL in ice_gnss_read error path")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/ethernet/intel/ice/ice_gnss.c b/drivers/net/ethernet/intel/ice/ice_gnss.c
index 12086aafb42fb..bd0ed155e11b6 100644
--- a/drivers/net/ethernet/intel/ice/ice_gnss.c
+++ b/drivers/net/ethernet/intel/ice/ice_gnss.c
@@ -85,6 +85,7 @@ static void ice_gnss_read(struct kthread_work *work)
{
struct gnss_serial *gnss = container_of(work, struct gnss_serial,
read_work.work);
+ unsigned long delay = ICE_GNSS_POLL_DATA_DELAY_TIME;
unsigned int i, bytes_read, data_len, count;
struct ice_aqc_link_topo_addr link_topo;
struct ice_pf *pf;
@@ -104,11 +105,6 @@ static void ice_gnss_read(struct kthread_work *work)
return;
hw = &pf->hw;
- buf = (char *)get_zeroed_page(GFP_KERNEL);
- if (!buf) {
- err = -ENOMEM;
- goto exit;
- }
memset(&link_topo, 0, sizeof(struct ice_aqc_link_topo_addr));
link_topo.topo_params.index = ICE_E810T_GNSS_I2C_BUS;
@@ -119,25 +115,24 @@ static void ice_gnss_read(struct kthread_work *work)
i2c_params = ICE_GNSS_UBX_DATA_LEN_WIDTH |
ICE_AQC_I2C_USE_REPEATED_START;
- /* Read data length in a loop, when it's not 0 the data is ready */
- for (i = 0; i < ICE_MAX_UBX_READ_TRIES; i++) {
- err = ice_aq_read_i2c(hw, link_topo, ICE_GNSS_UBX_I2C_BUS_ADDR,
- cpu_to_le16(ICE_GNSS_UBX_DATA_LEN_H),
- i2c_params, (u8 *)&data_len_b, NULL);
- if (err)
- goto exit_buf;
+ err = ice_aq_read_i2c(hw, link_topo, ICE_GNSS_UBX_I2C_BUS_ADDR,
+ cpu_to_le16(ICE_GNSS_UBX_DATA_LEN_H),
+ i2c_params, (u8 *)&data_len_b, NULL);
+ if (err)
+ goto requeue;
- data_len = be16_to_cpu(data_len_b);
- if (data_len != 0 && data_len != U16_MAX)
- break;
+ data_len = be16_to_cpu(data_len_b);
+ if (data_len == 0 || data_len == U16_MAX)
+ goto requeue;
- mdelay(10);
- }
+ /* The u-blox has data_len bytes for us to read */
data_len = min_t(typeof(data_len), data_len, PAGE_SIZE);
- if (!data_len) {
+
+ buf = (char *)get_zeroed_page(GFP_KERNEL);
+ if (!buf) {
err = -ENOMEM;
- goto exit_buf;
+ goto requeue;
}
/* Read received data */
@@ -151,7 +146,7 @@ static void ice_gnss_read(struct kthread_work *work)
cpu_to_le16(ICE_GNSS_UBX_EMPTY_DATA),
bytes_read, &buf[i], NULL);
if (err)
- goto exit_buf;
+ goto free_buf;
}
count = gnss_insert_raw(pf->gnss_dev, buf, i);
@@ -159,10 +154,11 @@ static void ice_gnss_read(struct kthread_work *work)
dev_warn(ice_pf_to_dev(pf),
"gnss_insert_raw ret=%d size=%d\n",
count, i);
-exit_buf:
+ delay = ICE_GNSS_TIMER_DELAY_TIME;
+free_buf:
free_page((unsigned long)buf);
- kthread_queue_delayed_work(gnss->kworker, &gnss->read_work,
- ICE_GNSS_TIMER_DELAY_TIME);
+requeue:
+ kthread_queue_delayed_work(gnss->kworker, &gnss->read_work, delay);
exit:
if (err)
dev_dbg(ice_pf_to_dev(pf), "GNSS failed to read err=%d\n", err);
diff --git a/drivers/net/ethernet/intel/ice/ice_gnss.h b/drivers/net/ethernet/intel/ice/ice_gnss.h
index d95ca3928b2ea..d206afe550a56 100644
--- a/drivers/net/ethernet/intel/ice/ice_gnss.h
+++ b/drivers/net/ethernet/intel/ice/ice_gnss.h
@@ -5,6 +5,7 @@
#define _ICE_GNSS_H_
#define ICE_E810T_GNSS_I2C_BUS 0x2
+#define ICE_GNSS_POLL_DATA_DELAY_TIME (HZ / 100) /* poll every 10 ms */
#define ICE_GNSS_TIMER_DELAY_TIME (HZ / 10) /* 0.1 second per message */
#define ICE_GNSS_TTY_WRITE_BUF 250
#define ICE_MAX_I2C_DATA_SIZE FIELD_MAX(ICE_AQC_I2C_DATA_SIZE_M)
@@ -20,8 +21,6 @@
* passed as I2C addr parameter.
*/
#define ICE_GNSS_UBX_WRITE_BYTES (ICE_MAX_I2C_WRITE_BYTES + 1)
-#define ICE_MAX_UBX_READ_TRIES 255
-#define ICE_MAX_UBX_ACK_READ_TRIES 4095
/**
* struct gnss_serial - data used to initialize GNSS TTY port
