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 ECF7638F935 for ; Thu, 27 Aug 2026 04:40:10 +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=1787805612; cv=none; b=WkucYurBjovNvVyJGPg3q2ixgBBg3gNkOFfgyMyX/Pba8wXpNkETF29s6kYo7o3XIBoJQiwnUBrD2gTMAk6jpFrm1kr8X76QCeIV9Owq6fKBr4AiDN3J2oGB4YHBfKShBfJ6kUmVOSZ83EPyjB3wB3OI4qDCQM+3BQhk7EWH4w0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787805612; c=relaxed/simple; bh=2UMFA1CfdBdsczLSK9sjfVZ/0wyGD4ZTPzwpEX0r8Hs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YHONVZABHyf4UVdCb57kBpeaaE1qcjKYNCVRmrnwaaci3XiIhVvCdeQZcxrlZM3IVdN2YOPaMNInl5pF6Yml8xf7i1VpGx4a3n3kIH1PbV5MlFuIuyuVJIi43D7P68ErF6w84Q40WuPD2Ow1UKgEPU04hfm+8if0z836ubTPhXI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZdEo4722; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZdEo4722" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 442D91F00A3E; Thu, 27 Aug 2026 04:40:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787805610; bh=5CbsEqmDirjdFSbzKTJdU9APnp9lJ0Y2huDNp8OmpM4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ZdEo47223VVzkYGP0Qvw22YwoePzCX+a+3mYsk7XzT2DqWkP14IZYhiDhp4K96WNN i7QhZQ0j4p2IZrzbx86jEs2X6yZpdZ6nS1HPNmSjTSP6h0fDR5D3HZEmqyNHAInDwu BUZuq1bh2zwqZgNRqHxcygvYq+VgK8IVpKSHBMtZEfD8a4EwAPLzx1Q0jbSL8DELiM AWDWxOYFMrQmUeERA8Y+nAcXx+1xiTccueKknweCQ0Z2mqdLS/VPg7NVUUywmc1Xo5 knZICnQImqcVpNnq1QAvmkXVW/RY3jDVANIUC5XzKLCTWxqyclf/+FDH73Y9Jm5HtA /dDzHRQWaEESA== From: Sasha Levin To: stable@vger.kernel.org Cc: Michael Zaidman , Enrik Berkhan , Jiri Kosina , Sasha Levin Subject: [PATCH 5.15.y 3/8] HID: ft260: improve i2c large reads performance Date: Thu, 27 Aug 2026 00:40:01 -0400 Message-ID: <20260827044007.3635916-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260827044007.3635916-1-sashal@kernel.org> References: <2026082538-obstacle-cogwheel-cfc1@gregkh> <20260827044007.3635916-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Michael Zaidman [ Upstream commit 54410c14800ad652c77e5c6fc5c17baad6e42cb6 ] The patch increases the read buffer size to 180 bytes. It reduces the number of ft260_i2c_read() calls by three, improving the big reads performance. $ sudo i2ctransfer -y -f 13 w2@0x51 0x0 0x0 r180 Before: [ +4.071878] ft260_i2c_write_read: off 0x0 rlen 180 wlen 2 [ +0.000005] ft260_i2c_write: rep 0xd0 addr 0x51 off 0 len 2 wlen 2 flag 0x2 d[0] 0x0 [ +0.001097] ft260_xfer_status: bus_status 0x41, clock 100 [ +0.000175] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.000004] ft260_i2c_read: rep 0xc2 addr 0x51 len 180 rlen 60 flag 0x3 [ +0.008579] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.000208] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.000001] ft260_i2c_read: rep 0xc2 addr 0x51 len 120 rlen 60 flag 0x0 [ +0.008794] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.000181] ft260_xfer_status: bus_status 0x40, clock 100 [ +0.000002] ft260_i2c_read: rep 0xc2 addr 0x51 len 60 rlen 60 flag 0x4 [ +0.008817] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.000223] ft260_xfer_status: bus_status 0x20, clock 100 After: [ +11.611642] ft260_i2c_write_read: off 0x0 rlen 180 wlen 2 [ +0.000005] ft260_i2c_write: rep 0xd0 addr 0x51 off 0 len 2 wlen 2 flag 0x2 d[0] 0x0 [ +0.008001] ft260_xfer_status: bus_status 0x20, clock 100 [ +0.000001] ft260_i2c_read: rep 0xc2 addr 0x51 len 180 rlen 180 flag 0x7 [ +0.008994] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.007987] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.007992] ft260_raw_event: i2c resp: rep 0xde len 60 [ +0.000206] ft260_xfer_status: bus_status 0x20, clock 100 Suggested-by: Enrik Berkhan Signed-off-by: Michael Zaidman 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 --- drivers/hid/hid-ft260.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c index 539d311bb9b9d..854876b16880d 100644 --- a/drivers/hid/hid-ft260.c +++ b/drivers/hid/hid-ft260.c @@ -30,12 +30,19 @@ 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) + * The ft260 input report format defines 62 bytes for the data payload, but + * when requested 62 bytes, the controller returns 60 and 2 in separate input + * reports. To achieve better performance with the multi-report read data + * transfers, we set the maximum read payload length to a multiple of 60. + * With a 100 kHz I2C clock, one 240 bytes read takes about 1/27 second, + * which is excessive; On the other hand, some higher layer drivers like at24 + * or optoe limit the i2c reads to 128 bytes. To not block other drivers out + * of I2C for potentially troublesome amounts of time, we select the maximum + * read payload length to be 180 bytes. +*/ +#define FT260_RD_DATA_MAX (180) #define FT260_WR_DATA_MAX (60) /* -- 2.53.0