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From:   Michael Zaidman <michael.zaidman@gmail.com>
To:     jikos@kernel.org
Cc:     linux-kernel@vger.kernel.org, linux-input@vger.kernel.org,
        Michael Zaidman <michael.zaidman@gmail.com>,
        Guillaume Champagne <champagne.guillaume.c@gmail.com>
Subject: [PATCH v2 5/7] HID: ft260: improve i2c large reads performance
Date:   Wed, 28 Sep 2022 17:48:52 +0300
Message-Id: <20220928144854.5580-6-michael.zaidman@gmail.com>
In-Reply-To: <20220928144854.5580-1-michael.zaidman@gmail.com>
References: <20220928144854.5580-1-michael.zaidman@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The patch increases the read buffer size to 128 bytes. It reduces the
number of ft260_i2c_read calls by three and improves the large data
chunks' read performance by about 10%.

Before:

$ sudo ./i2cperf -d 2 -o 2 -s 128 -r 0-0xff 13 0x51 -S

  Read block via i2ctransfer by chunks
  -------------------------------------------------------------------
  data rate(bps)  efficiency(%)  data size(B)  total IOs   IO size(B)
  -------------------------------------------------------------------
  43990           85             256           2           128

Kernel log:

[  +1.464346] ft260_i2c_write_read: off 0x0 rlen 128 wlen 2
[  +0.000002] ft260_i2c_write: rep 0xd0 addr 0x51 off 0 len 2 wlen 2 flag 0x2 d[0] 0x0
[  +0.001653] ft260_xfer_status: bus_status 0x41, clock 100
[  +0.000188] ft260_xfer_status: bus_status 0x40, clock 100
[  +0.000002] ft260_i2c_read: rep 0xc2 addr 0x51 len 128 rlen 60 flag 0x3
[  +0.008609] ft260_raw_event: i2c resp: rep 0xde len 60
[  +0.000157] ft260_xfer_status: bus_status 0x40, clock 100
[  +0.000002] ft260_i2c_read: rep 0xc2 addr 0x51 len 68 rlen 60 flag 0x0
[  +0.008840] ft260_raw_event: i2c resp: rep 0xde len 60
[  +0.000203] ft260_xfer_status: bus_status 0x40, clock 100
[  +0.000002] ft260_i2c_read: rep 0xc2 addr 0x51 len 8 rlen 8 flag 0x4
[  +0.002794] ft260_raw_event: i2c resp: rep 0xd1 len 8
[  +0.000201] ft260_xfer_status: bus_status 0x20, clock 100
[  +0.015171] ft260_i2c_write_read: off 0x80 rlen 128 wlen 2
[  +0.000002] ft260_i2c_write: rep 0xd0 addr 0x51 off 0 len 2 wlen 2 flag 0x2 d[0] 0x0
[  +0.000764] ft260_xfer_status: bus_status 0x41, clock 100
[  +0.000231] ft260_xfer_status: bus_status 0x41, clock 100
[  +0.000148] ft260_xfer_status: bus_status 0x40, clock 100
[  +0.000002] ft260_i2c_read: rep 0xc2 addr 0x51 len 128 rlen 60 flag 0x3
[  +0.008488] ft260_raw_event: i2c resp: rep 0xde len 60
[  +0.000205] ft260_xfer_status: bus_status 0x40, clock 100
[  +0.000002] ft260_i2c_read: rep 0xc2 addr 0x51 len 68 rlen 60 flag 0x0
[  +0.008795] ft260_raw_event: i2c resp: rep 0xde len 60
[  +0.000176] ft260_xfer_status: bus_status 0x40, clock 100
[  +0.000001] ft260_i2c_read: rep 0xc2 addr 0x51 len 8 rlen 8 flag 0x4
[  +0.002819] ft260_raw_event: i2c resp: rep 0xd1 len 8
[  +0.000167] ft260_xfer_status: bus_status 0x20, clock 100

After:

$ sudo ./i2cperf -d 2 -o 2 -s 128 -r 0-0xff 13 0x51 -S

  Read block via i2ctransfer by chunks
  -------------------------------------------------------------------
  data rate(bps)  efficiency(%)  data size(B)  total IOs   IO size(B)
  -------------------------------------------------------------------
  49316           85             256           2           128

Kernel log:

[  +1.447360] ft260_i2c_write_read: off 0x0 rlen 128 wlen 2
[  +0.000002] ft260_i2c_write: rep 0xd0 addr 0x51 off 0 len 2 wlen 2 flag 0x2 d[0] 0x0
[  +0.001633] ft260_xfer_status: bus_status 0x41, clock 100
[  +0.000190] ft260_xfer_status: bus_status 0x40, clock 100
[  +0.000001] ft260_i2c_read: rep 0xc2 addr 0x51 len 128 rlen 128 flag 0x7
[  +0.008617] ft260_raw_event: i2c resp: rep 0xde len 60
[  +0.008033] ft260_raw_event: i2c resp: rep 0xde len 60
[  +0.000954] ft260_raw_event: i2c resp: rep 0xd1 len 8
[  +0.000208] ft260_xfer_status: bus_status 0x20, clock 100
[  +0.015853] ft260_i2c_write_read: off 0x80 rlen 128 wlen 2
[  +0.000002] ft260_i2c_write: rep 0xd0 addr 0x51 off 0 len 2 wlen 2 flag 0x2 d[0] 0x0
[  +0.001182] ft260_xfer_status: bus_status 0x41, clock 100
[  +0.000180] ft260_xfer_status: bus_status 0x40, clock 100
[  +0.000001] ft260_i2c_read: rep 0xc2 addr 0x51 len 128 rlen 128 flag 0x7
[  +0.008575] ft260_raw_event: i2c resp: rep 0xde len 60
[  +0.008014] ft260_raw_event: i2c resp: rep 0xde len 60
[  +0.001001] ft260_raw_event: i2c resp: rep 0xd1 len 8
[  +0.000223] ft260_xfer_status: bus_status 0x20, clock 100

Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>
Tested-by: Guillaume Champagne <champagne.guillaume.c@gmail.com>
---
 drivers/hid/hid-ft260.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c
index cb8f1782d1f0..c7c3a9d395a2 100644
--- a/drivers/hid/hid-ft260.c
+++ b/drivers/hid/hid-ft260.c
@@ -30,12 +30,8 @@ MODULE_PARM_DESC(debug, "Toggle FT260 debugging messages");
 
 #define FT260_REPORT_MAX_LENGTH (64)
 #define FT260_I2C_DATA_REPORT_ID(len) (FT260_I2C_REPORT_MIN + (len - 1) / 4)
-/*
- * The input report format assigns 62 bytes for the data payload, but ft260
- * returns 60 and 2 in two separate transactions. To minimize transfer time
- * in reading chunks mode, set the maximum read payload length to 60 bytes.
- */
-#define FT260_RD_DATA_MAX (60)
+
+#define FT260_RD_DATA_MAX (128)
 #define FT260_WR_DATA_MAX (60)
 
 /*
-- 
2.34.1