[PATCH v1 2/5] HID: ft260: improve i2c write performance

Michael Zaidman
2022-05-25T07:48:53Z

The patch improves i2c writing performance by about 30 percent by revising the
sleep time in the ft260_hid_output_report_check_status() in the following ways:

1. Reduce the sleep time and start to poll earlier:

Before:
$ sudo ./i2cperf -f 2 -o 2 -s 32 -r 0-0xff 13 0x51 -S

Fill block with increment via i2ctransfer by chunks
-------------------------------------------------------------------
data rate(bps) efficiency(%) data size(B) total IOs IO size(B)
-------------------------------------------------------------------
40510 80 256 8 32

After:
$ sudo ./i2cperf -f 2 -o 2 -s 32 -r 0-0xff 13 0x51 -S

Fill block with increment via i2ctransfer by chunks
-------------------------------------------------------------------
data rate(bps) efficiency(%) data size(B) total IOs IO size(B)
-------------------------------------------------------------------
52584 80 256 8 32

2. Do not sleep when the calculated sleep time is below 2 ms:

Before:
$ sudo ./i2cperf -f 2 -o 2 -s 16 -r 0-0xff 13 0x51 -S

Fill block with increment via i2ctransfer by chunks
-------------------------------------------------------------------
data rate(bps) efficiency(%) data size(B) total IOs IO size(B)
-------------------------------------------------------------------
26707 73 256 16 16

After:
$ sudo ./i2cperf -f 2 -o 2 -s 16 -r 0-0xff 13 0x51 -S

Fill block with increment via i2ctransfer by chunks
-------------------------------------------------------------------
data rate(bps) efficiency(%) data size(B) total IOs IO size(B)
-------------------------------------------------------------------
37034 73 256 16 16

Link to the i2cperf - https://github.com/MichaelZaidman/i2cperf

Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>
---
drivers/hid/hid-ft260.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c
index a35201d68b15..44106cadd746 100644
--- a/drivers/hid/hid-ft260.c
+++ b/drivers/hid/hid-ft260.c
@@ -345,7 +345,7 @@ static int ft260_hid_output_report(struct hid_device *hdev, u8 *data,
static int ft260_hid_output_report_check_status(struct ft260_device *dev,
u8 *data, int len)
{
- int ret, usec, try = 3;
+ int ret, usec, try = 100;
struct hid_device *hdev = dev->hdev;

ret = ft260_hid_output_report(hdev, data, len);
@@ -356,10 +356,14 @@ static int ft260_hid_output_report_check_status(struct ft260_device *dev,
return ret;
}

- /* transfer time = 1 / clock(KHz) * 10 bits * bytes */
- usec = 10000 / dev->clock * len;
- usleep_range(usec, usec + 100);
- ft260_dbg("wait %d usec, len %d\n", usec, len);
+ /* transfer time = 1 / clock(KHz) * 9 bits * bytes */
+ usec = len * 9000 / dev->clock;
+ if (usec > 2000) {
+ usec -= 1500;
+ usleep_range(usec, usec + 100);
+ ft260_dbg("wait %d usec, len %d\n", usec, len);
+ }
+
do {
ret = ft260_xfer_status(dev);
if (ret != -EAGAIN)
--
2.25.1