[6/6] platform/x86: dell-smo8800: Add support for probing for the accelerometer i2c address

Message ID	20231224213629.395741-7-hdegoede@redhat.com (mailing list archive)
State	Superseded, archived
Headers	show Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 83183101F4 for <platform-driver-x86@vger.kernel.org>; Sun, 24 Dec 2023 21:36:57 +0000 (UTC) From: Hans de Goede <hdegoede@redhat.com> To: =?utf-8?q?Pali_Roh=C3=A1r?= <pali@kernel.org>, Jean Delvare <jdelvare@suse.com>, Andi Shyti <andi.shyti@kernel.org>, Eric Piel <eric.piel@tremplin-utc.net> Cc: Hans de Goede <hdegoede@redhat.com>, Paul Menzel <pmenzel@molgen.mpg.de>, =?utf-8?q?Ilpo_J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>, Andy Shevchenko <andy@kernel.org>, Dell.Client.Kernel@dell.com, Marius Hoch <mail@mariushoch.de>, Kai Heng Feng <kai.heng.feng@canonical.com>, Wolfram Sang <wsa@kernel.org>, platform-driver-x86@vger.kernel.org, linux-i2c@vger.kernel.org Subject: [PATCH 6/6] platform/x86: dell-smo8800: Add support for probing for the accelerometer i2c address Date: Sun, 24 Dec 2023 22:36:22 +0100 Message-ID: <20231224213629.395741-7-hdegoede@redhat.com> In-Reply-To: <20231224213629.395741-1-hdegoede@redhat.com> References: <20231224213629.395741-1-hdegoede@redhat.com> Precedence: bulk MIME-Version: 1.0 Content-Transfer-Encoding: 8bit
Series	i2c-i801 / dell-smo8800: Move instantiation of lis3lv02d i2c_client from i2c-i801 to dell-smo8800 \| expand [0/6] i2c-i801 / dell-smo8800: Move instantiation of lis3lv02d i2c_client from i2c-i801 to dell-smo… [1/6] platform/x86: dell-smo8800: Only load on Dell laptops [2/6] platform/x86: dell-smo8800: Change probe() ordering a bit [3/6] platform/x86: dell-smo8800: Move instantiation of lis3lv02d i2c_client from i2c-i801 to dell-… [4/6] platform/x86: dell-smo8800: Pass the IRQ to the lis3lv02d i2c_client [5/6] platform/x86: dell-smo8800: Instantiate an i2c_client for the IIO st_accel driver [6/6] platform/x86: dell-smo8800: Add support for probing for the accelerometer i2c address

diff --git a/drivers/platform/x86/dell/dell-smo8800.c b/drivers/platform/x86/dell/dell-smo8800.c index bb1d3e439761..60ce2695ce01 100644 --- a/drivers/platform/x86/dell/dell-smo8800.c +++ b/drivers/platform/x86/dell/dell-smo8800.c @@ -29,6 +29,10 @@ static bool use_misc_lis3lv02d; module_param(use_misc_lis3lv02d, bool, 0444); MODULE_PARM_DESC(use_misc_lis3lv02d, "Use /dev/freefall chardev + evdev joystick emulation instead of iio accel driver"); +static bool probe_i2c_addr; +module_param(probe_i2c_addr, bool, 0444); +MODULE_PARM_DESC(probe_i2c_addr, "Probe the i801 I2C bus for the accelerometer on models where the address is unknown"); + struct smo8800_device { u32 irq; /* acpi device irq */ atomic_t counter; /* count after last read */ @@ -146,6 +150,82 @@ static int smo8800_find_i801(struct device *dev, void *data) return 1; } +/* + * This is the kernel version of the single register device sanity checks from + * the i2c_safety_check function from lm_sensors sensor-detect script: + * This is meant to prevent access to 1-register-only devices, + * which are designed to be accessed with SMBus receive byte and SMBus send + * byte transactions (i.e. short reads and short writes) and treat SMBus + * read byte as a real write followed by a read. The device detection + * routines would write random values to the chip with possibly very nasty + * results for the hardware. Note that this function won't catch all such + * chips, as it assumes that reads and writes relate to the same register, + * but that's the best we can do. + */ +static int i2c_safety_check(struct smo8800_device *smo8800, struct i2c_adapter *adap, u8 addr) +{ + union i2c_smbus_data smbus_data; + int err; + u8 data; + + /* + * First receive a byte from the chip, and remember it. This + * also checks if there is a device at the address at all. + */ + err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0, + I2C_SMBUS_BYTE, &smbus_data); + if (err < 0) + return err; + + data = smbus_data.byte; + + /* + * Receive a byte again; very likely to be the same for + * 1-register-only devices. + */ + err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0, + I2C_SMBUS_BYTE, &smbus_data); + if (err < 0) + return err; + + if (smbus_data.byte != data) + return 0; /* Not a 1-register-only device. */ + + /* + * Then try a standard byte read, with a register offset equal to + * the read byte; for 1-register-only device this should read + * the same byte value in return. + */ + err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, data, + I2C_SMBUS_BYTE_DATA, &smbus_data); + if (err < 0) + return err; + + if (smbus_data.byte != data) + return 0; /* Not a 1-register-only device. */ + + /* + * Then try a standard byte read, with a slightly different register + * offset; this should again read the register offset in return. + */ + err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, data ^ 0x01, + I2C_SMBUS_BYTE_DATA, &smbus_data); + if (err < 0) + return err; + + if (smbus_data.byte != (data ^ 0x01)) + return 0; /* Not a 1-register-only device. */ + + /* + * Apparently this is a 1-register-only device, restore the original + * register value and leave it alone. + */ + i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_WRITE, data, + I2C_SMBUS_BYTE, NULL); + dev_warn(smo8800->dev, "I2C safety check for address 0x%02x failed, skipping\n", addr); + return -ENODEV; +} + /* * Set label to let iio-sensor-proxy know these freefall sensors are located in * the laptop base (not the display) and are not intended for screen rotation. @@ -161,12 +241,19 @@ const struct software_node smo8800_accel_node = { static int smo8800_detect_accel(struct smo8800_device *smo8800, struct i2c_adapter *adap, u8 addr, - struct i2c_board_info *info) + struct i2c_board_info *info, bool probe) { union i2c_smbus_data smbus_data; const char *type; int err; + if (probe) { + dev_info(smo8800->dev, "Probing for accelerometer on address 0x%02x\n", addr); + err = i2c_safety_check(smo8800, adap, addr); + if (err < 0) + return err; + } + err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, LIS3_WHO_AM_I, I2C_SMBUS_BYTE_DATA, &smbus_data); if (err < 0) { @@ -253,17 +340,25 @@ static void smo8800_instantiate_i2c_client(struct smo8800_device *smo8800) } } - if (!addr) { + if (addr) { + /* Always detect the accel-type, this also checks the accel is actually there */ + err = smo8800_detect_accel(smo8800, adap, addr, &info, false); + if (err) + goto put_adapter; + } else if (probe_i2c_addr) { + /* First try address 0x29 (most used) and then try 0x1d */ + if (smo8800_detect_accel(smo8800, adap, 0x29, &info, true) != 0 && + smo8800_detect_accel(smo8800, adap, 0x1d, &info, true) != 0) { + dev_warn(smo8800->dev, "No accelerometer found\n"); + goto put_adapter; + } + } else { dev_warn(smo8800->dev, "Accelerometer lis3lv02d is present on SMBus but its address is unknown, skipping registration\n"); + dev_info(smo8800->dev, "Pass dell_smo8800.probe_i2c_addr=1 on the kernel commandline to probe, this may be dangerous!\n"); goto put_adapter; } - /* Always detect the accel-type, this also checks the accel is actually there */ - err = smo8800_detect_accel(smo8800, adap, addr, &info); - if (err) - goto put_adapter; - /* * If requested override detected type with "lis3lv02d" i2c_client_id, * for the old drivers/misc/lis3lv02d/lis3lv02d.c driver. @@ -281,6 +376,9 @@ static void smo8800_instantiate_i2c_client(struct smo8800_device *smo8800) } else { dev_info(smo8800->dev, "Registered %s accelerometer on address 0x%02x\n", info.type, info.addr); + if (!addr) + dev_info(smo8800->dev, + "Please report this address upstream together with the output of 'cat /sys/class/dmi/id/product_name'\n"); } put_adapter: i2c_put_adapter(adap);

[6/6] platform/x86: dell-smo8800: Add support for probing for the accelerometer i2c address

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