Some newer Thinkpads have the WLAN antenna placed close to the WWAN antenna. In these cases FCC certification requires that when WWAN is active we reduce WLAN transmission power. A new Dynamic Power Reduction Control (DPRC) method is available from the BIOS on these platforms to reduce or restore WLAN Tx power. This patch provides a sysfs interface that userspace can use to adjust the WLAN power appropriately. Reviewed-by: Mark Pearson <markpearson@xxxxxxxxxx> Signed-off-by: Nitin Joshi <njoshi1@xxxxxxxxxx> --- .../admin-guide/laptops/thinkpad-acpi.rst | 18 +++ drivers/platform/x86/thinkpad_acpi.c | 130 ++++++++++++++++++ 2 files changed, 148 insertions(+) diff --git a/Documentation/admin-guide/laptops/thinkpad-acpi.rst b/Documentation/admin-guide/laptops/thinkpad-acpi.rst index 5fe1ade88c17..10410811b990 100644 --- a/Documentation/admin-guide/laptops/thinkpad-acpi.rst +++ b/Documentation/admin-guide/laptops/thinkpad-acpi.rst @@ -51,6 +51,7 @@ detailed description): - UWB enable and disable - LCD Shadow (PrivacyGuard) enable and disable - Lap mode sensor + - WLAN transmission power control A compatibility table by model and feature is maintained on the web site, http://ibm-acpi.sf.net/. I appreciate any success or failure @@ -1447,6 +1448,23 @@ they differ between desk and lap mode. The property is read-only. If the platform doesn't have support the sysfs class is not created. +WLAN transmission power control +-------------------------------- + +sysfs: wlan_tx_strength_reduce + +Some newer Thinkpads have the WLAN antenna placed close to the WWAN antenna. +This interface will be used by userspace to reduce the WLAN Tx power strength +when WWAN is active, as is required for FCC certification. + +The available commands are:: + + echo '0' > /sys/devices/platform/thinkpad_acpi/wlan_tx_strength_reduce + echo '1' > /sys/devices/platform/thinkpad_acpi/wlan_tx_strength_reduce + +The first command restores the wlan transmission power and the latter one +reduces wlan transmission power. + EXPERIMENTAL: UWB ----------------- diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c index f3e8eca8d86d..af90251d79d7 100644 --- a/drivers/platform/x86/thinkpad_acpi.c +++ b/drivers/platform/x86/thinkpad_acpi.c @@ -9983,6 +9983,132 @@ static struct ibm_struct proxsensor_driver_data = { .exit = proxsensor_exit, }; +/************************************************************************* + * DPRC(Dynamic Power Reduction Control) subdriver, for the Lenovo WWAN + * and WLAN feature. + */ +#define DPRC_GET_WLAN_STATE 0x20000 +#define DPRC_SET_WLAN_POWER_REDUCE 0x00030010 +#define DPRC_SET_WLAN_POWER_FULL 0x00030100 +#define DPRC_WLAN_POWER_REDUCE_BIT BIT(4) +#define DPRC_WLAN_POWER_FULL_BIT BIT(8) +static bool has_wlantxreduce; +static int wlan_txreduce; + +static int dprc_command(int command, int *output) +{ + acpi_handle dprc_handle; + + if (ACPI_FAILURE(acpi_get_handle(hkey_handle, "DPRC", &dprc_handle))) { + /* Platform doesn't support DPRC */ + return -ENODEV; + } + + if (!acpi_evalf(dprc_handle, output, NULL, "dd", command)) + return -EIO; + + /* + * METHOD_ERR gets returned on devices where few commands are not supported + * for example WLAN power reduce command is not supported on some devices. + */ + if (*output & METHOD_ERR) + return -ENODEV; + + return 0; +} + +static int get_wlan_state(int *wlan_txreduce) +{ + int output, err; + + /* Get current WLAN Power Transmission state */ + err = dprc_command(DPRC_GET_WLAN_STATE, &output); + if (err) + return err; + + if (output & DPRC_WLAN_POWER_REDUCE_BIT) + *wlan_txreduce = 1; + else if (output & DPRC_WLAN_POWER_FULL_BIT) + *wlan_txreduce = 0; + else + return -ENODATA; + + return 0; +} + +/* sysfs wlan entry */ +static ssize_t wlan_tx_strength_reduce_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + int err; + + err = get_wlan_state(&wlan_txreduce); + if (err) + return err; + + return sysfs_emit(buf, "%d\n", wlan_txreduce); +} + +static ssize_t wlan_tx_strength_reduce_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + int output, err, ret; + bool state; + + ret = kstrtobool(buf, &state); + if (ret) + return ret; + + if (state) + err = dprc_command(DPRC_SET_WLAN_POWER_REDUCE, &output); + else + err = dprc_command(DPRC_SET_WLAN_POWER_FULL, &output); + + sysfs_notify(&tpacpi_pdev->dev.kobj, NULL, "wlan_tx_strength_reduce"); + + return count; +} +static DEVICE_ATTR_RW(wlan_tx_strength_reduce); + +static int tpacpi_dprc_init(struct ibm_init_struct *iibm) +{ + int wlantx_err, err; + + wlantx_err = get_wlan_state(&wlan_txreduce); + /* + * If support isn't available (ENODEV) for both devices then quit, but + * don't return an error. + */ + if ((wlantx_err == -ENODEV) || (wlantx_err == -ENODATA)) + return 0; + /* Otherwise, if there was an error return it */ + if (wlantx_err && (wlantx_err != -ENODEV) && (wlantx_err != -ENODATA)) + return wlantx_err; + else if (!wlantx_err) + has_wlantxreduce = true; + + if (has_wlantxreduce) { + err = sysfs_create_file(&tpacpi_pdev->dev.kobj, + &dev_attr_wlan_tx_strength_reduce.attr); + if (err) + return err; + } + return 0; +} + +static void dprc_exit(void) +{ + if (has_wlantxreduce) + sysfs_remove_file(&tpacpi_pdev->dev.kobj, &dev_attr_wlan_tx_strength_reduce.attr); +} + +static struct ibm_struct dprc_driver_data = { + .name = "dprc", + .exit = dprc_exit, +}; + /**************************************************************************** **************************************************************************** * @@ -10475,6 +10601,10 @@ static struct ibm_init_struct ibms_init[] __initdata = { .init = tpacpi_proxsensor_init, .data = &proxsensor_driver_data, }, + { + .init = tpacpi_dprc_init, + .data = &dprc_driver_data, + }, }; static int __init set_ibm_param(const char *val, const struct kernel_param *kp) -- 2.25.1
