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([37.142.145.227]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-48e71b959c1sm5457300f8f.45.2026.10.30.15.37.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Oct 2026 15:37:22 -0700 (PDT) From: Michael Zaidman To: Jiri Kosina , Benjamin Tissoires Cc: Linus Walleij , Bartosz Golaszewski , Greg Kroah-Hartman , Jiri Slaby , Raman Varabets , Germain Hebert , Christina Quast , Rio Liu , Bruno Giacomazzi , linux-input@vger.kernel.org, linux-serial@vger.kernel.org, linux-gpio@vger.kernel.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Zaidman Subject: [PATCH v2 12/15] HID: ft260: i2c: abort in-flight transfers with STOP before reset Date: Sat, 31 Oct 2026 00:36:34 +0200 Message-ID: <20261030223637.86907-13-michael.zaidman@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261030223637.86907-1-michael.zaidman@gmail.com> References: <20261030223637.86907-1-michael.zaidman@gmail.com> X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A transfer that ends without STOP leaves the FT260 I2C controller with BUS_BUSY set. I2C reset (AN_394 section 4.4.15) restarts the master but, with the driver still bound, status stays 0x60 (CTRL_IDLE | BUS_BUSY) even when SCL and SDA are pulled up. The next START then fails with 0x72 (arbitration lost + error) and further resets do not recover; only a USB replug did. Add ft260_i2c_abort(): a STOP-only write (flag 0x04, zero payload) then FT260_SET_I2C_RESET. Use it wherever the host tears down an open transaction: - read wait timeout - read status check failure after the HID report arrived - write status poll failure after the report was sent - SMBus block read with an invalid count (count phase has no STOP) Leave ft260_i2c_reset() alone for HID output failure (the request may never have reached the controller), sysfs i2c_reset, and probe. Tested on a UMFT260EV1A with a 24LC512 at 0x51. Five 1 ms read timeouts each followed by STOP+reset left bus_status 0x20; raising the timeout to 25 ms on the same loaded module then read 16 bytes successfully. This matters more with the 25/75 ms completion timeout from "HID: ft260: i2c: reduce driver module loading time", which makes read timeouts more likely than mainline's 5000 ms wait. Signed-off-by: Michael Zaidman --- drivers/hid/hid-ft260.c | 43 ++++++++++++++++++++++++++++++++++------- 1 file changed, 36 insertions(+), 7 deletions(-) diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c index 923ce6ee9dcf..50f68790c04d 100644 --- a/drivers/hid/hid-ft260.c +++ b/drivers/hid/hid-ft260.c @@ -549,6 +549,33 @@ static int ft260_i2c_reset(struct hid_device *hdev) return ret; } +static int ft260_hid_output_report(struct hid_device *hdev, u8 *data, + size_t len); + +/* + * STOP with no START and no payload. Used by ft260_i2c_abort() when + * tearing down an in-flight transfer: I2C reset alone can leave + * BUS_BUSY set even when SCL/SDA are idle, and the next START then + * fails with arbitration lost. + */ +static int ft260_i2c_stop(struct hid_device *hdev, u8 addr) +{ + u8 buf[4] = { + FT260_I2C_REPORT_MIN, + addr, + FT260_FLAG_STOP, + 0, + }; + + return ft260_hid_output_report(hdev, buf, sizeof(buf)); +} + +static int ft260_i2c_abort(struct hid_device *hdev, u8 addr) +{ + ft260_i2c_stop(hdev, addr); + return ft260_i2c_reset(hdev); +} + static int ft260_xfer_status(struct ft260_device *dev, u8 bus_busy) { struct hid_device *hdev = dev->hdev; @@ -618,7 +645,8 @@ 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, u8 bus_busy) + u8 *data, int len, u8 addr, + u8 bus_busy) { int ret, usec, try = 100; struct hid_device *hdev = dev->hdev; @@ -647,7 +675,7 @@ static int ft260_hid_output_report_check_status(struct ft260_device *dev, if (ret == 0) return 0; - ft260_i2c_reset(hdev); + ft260_i2c_abort(hdev, addr); return -EIO; } @@ -686,7 +714,8 @@ static int ft260_i2c_write(struct ft260_device *dev, u8 addr, u8 *data, rep->flag, data[0]); ret = ft260_hid_output_report_check_status(dev, (u8 *)rep, - wr_len + 4, bus_busy); + wr_len + 4, addr, + bus_busy); if (ret < 0) { ft260_dbg("failed with %d\n", ret); return ret; @@ -727,7 +756,7 @@ static int ft260_smbus_write(struct ft260_device *dev, u8 addr, u8 cmd, ft260_dbg("rep %#02x addr %#02x cmd %#02x datlen %d replen %d\n", rep->report, addr, cmd, rep->length, len); - ret = ft260_hid_output_report_check_status(dev, (u8 *)rep, len, + ret = ft260_hid_output_report_check_status(dev, (u8 *)rep, len, addr, (flag & FT260_FLAG_STOP) ? FT260_I2C_STATUS_BUS_BUSY : 0); if (ret < 0) @@ -795,7 +824,7 @@ static int ft260_i2c_read(struct ft260_device *dev, u8 addr, u8 *data, timeout_jiffies = msecs_to_jiffies(timeout); if (!wait_for_completion_timeout(&dev->wait, timeout_jiffies)) { ret = -ETIMEDOUT; - ft260_i2c_reset(hdev); + ft260_i2c_abort(hdev, addr); goto ft260_i2c_read_exit; } @@ -809,7 +838,7 @@ static int ft260_i2c_read(struct ft260_device *dev, u8 addr, u8 *data, ret = ft260_xfer_status(dev, bus_busy); if (ret < 0) { ret = -EIO; - ft260_i2c_reset(hdev); + ft260_i2c_abort(hdev, addr); goto ft260_i2c_read_exit; } @@ -993,7 +1022,7 @@ static int ft260_smbus_xfer(struct i2c_adapter *adapter, u16 addr, u16 flags, hid_warn(hdev, "smbus block read: invalid count %u from slave 0x%02x\n", count, addr); - ft260_i2c_reset(hdev); + ft260_i2c_abort(hdev, addr); ret = -EPROTO; goto smbus_exit; } -- 2.43.0