From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CD8EF481FA0; Mon, 31 Aug 2026 14:04:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788185043; cv=none; b=lmiZ+1WQSUlzaA8s/bPc+mTO6MMayA7LyYMorCIfzNJUTwJJe+7qhW4DqrX+aKGr0c7itwbJkmdnwvwUxbqAgvcmepLNDaD8BFKpkr8RlXPVsUi/xc/NLt54hkBEfsC681xn2qLF9rQOOKNpNJm76umJOuhDus4H5lv6QAcrM8Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788185043; c=relaxed/simple; bh=MZgVK2zSu6eOFmrDDK4OUaBS94mTSNGRZ7py7Ii9/Ic=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Uu8RWyH7nXYYNVapQP4hwi8L1O/AhJdUK6AMF8Hdo6iWFrI5ZNpZTLNSvRuQZ4La/DTpjIHHjZ2fjhkgzjMrgkARqOrJVwrC7w6faK2cNz1vA8DiRVkrnbfpilJE7UbTK8n8OCRkRL4SnVyfIHyw3CExchUVQQDAh5Yb7HfRbVY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=WxHWOMF5; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="WxHWOMF5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 34B451F00A3D; Mon, 31 Aug 2026 14:04:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788185041; bh=XyibLalD2xLQZVxfk40nXcX7EFIoPiaIbX9pU68rBDI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WxHWOMF5S1hBffwIpFUeLCMT5t5HwIUske/eTDJcBxW5dMCyLtluT3b3XBTALbGq7 j1lFXM64jt39TDN1NKICkfED3w5R+VsSprvTmYlPHH6RzX5d/zhot/0w82RAo+04da JVZYLFPifynET4p1LPbUtZWEIrJmHa6yOxzyfXgo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Michael Zaidman , Guillaume Champagne , Jiri Kosina , Sasha Levin Subject: [PATCH 5.15 34/69] HID: ft260: improve i2c write performance Date: Mon, 31 Aug 2026 15:35:07 +0200 Message-ID: <20260831133400.218362889@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260831133358.601894154@linuxfoundation.org> References: <20260831133358.601894154@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Michael Zaidman [ Upstream commit 6fca5e3f5574ca1bd5bade5737848c816f924c6a ] The patch improves the I2C write performance by 20 - 30 percent by revising the sleep time in the ft260_hid_output_report_check_status() in the following ways: 1. Reduce the wait time and start to poll earlier. Sending a large amount of data at a low I2C clock rate saturates the internal FT260 buffer and causes hiccups in status readiness, as shown below in the log fragment. Aligning the status check wait time to the worst case significantly reduces the write performance. [Oct22 10:28] ft260_i2c_write: rep 0xd8 addr 0x51 off 0 len 34 d[0] 0x0 [ +0.005296] ft260_xfer_status: bus_status 0x20, clock 100 [ +0.013460] ft260_i2c_write: rep 0xd8 addr 0x51 off 0 len 34 d[0] 0x0 [ +0.003244] ft260_hid_output_report_check_status: wait 1920 usec, len 38 [ +0.000190] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.015324] ft260_i2c_write: rep 0xd8 addr 0x51 off 0 len 34 d[0] 0x0 [ +0.003491] ft260_hid_output_report_check_status: wait 1920 usec, len 38 [ +0.000202] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.016047] ft260_i2c_write: rep 0xd8 addr 0x51 off 0 len 34 d[0] 0x0 [ +0.002768] ft260_hid_output_report_check_status: wait 1920 usec, len 38 [ +0.000150] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.011389] ft260_i2c_write: rep 0xd8 addr 0x51 off 0 len 34 d[0] 0x0 [ +0.003467] ft260_hid_output_report_check_status: wait 1920 usec, len 38 [ +0.000191] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000172] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000131] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000241] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000233] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000190] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000196] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.011314] ft260_i2c_write: rep 0xd8 addr 0x51 off 0 len 34 d[0] 0x0 [ +0.003334] ft260_hid_output_report_check_status: wait 1920 usec, len 38 [ +0.000227] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000204] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000198] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000147] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.011060] ft260_i2c_write: rep 0xd8 addr 0x51 off 0 len 34 d[0] 0x0 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 if the estimated I2C transfer time is below 2 ms since the first xfer status query frequently takes around 1.5 ms, and the following status queries take about 200us on average. So we usually return from the routine after the first 1 - 3 status checks. [Oct22 11:14] ft260_i2c_write: rep 0xd4 addr 0x51 off 0 len 18 d[0] 0x0 [ +0.004270] ft260_xfer_status: bus_status 0x20, clock 100 [ +0.013889] ft260_i2c_write: rep 0xd4 addr 0x51 off 0 len 18 d[0] 0x0 [ +0.000856] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000138] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.013352] ft260_i2c_write: rep 0xd4 addr 0x51 off 0 len 18 d[0] 0x0 [ +0.001501] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000177] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.014477] ft260_i2c_write: rep 0xd4 addr 0x51 off 0 len 18 d[0] 0x0 [ +0.001377] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000233] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000191] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.013197] ft260_i2c_write: rep 0xd4 addr 0x51 off 0 len 18 d[0] 0x0 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) ------------------------------------------------------------------- 28826 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) ------------------------------------------------------------------- 45138 73 256 16 16 Signed-off-by: Michael Zaidman Tested-by: Guillaume Champagne Signed-off-by: Jiri Kosina Stable-dep-of: bf3e39df3a39 ("HID: ft260: fix stack-use-after-return write in I2C read race") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/hid/hid-ft260.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) --- a/drivers/hid/hid-ft260.c +++ b/drivers/hid/hid-ft260.c @@ -355,7 +355,7 @@ static int ft260_hid_output_report(struc 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); @@ -366,10 +366,14 @@ static int ft260_hid_output_report_check 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)