• Evan Green's avatar
    iio: adc: qcom-spmi-adc5: Initialize prescale properly · db23d887
    Evan Green authored
    adc5_get_dt_data uses a local, prop, feeds it to adc5_get_dt_channel_data,
    and then puts the result into adc->chan_props. The problem is
    adc5_get_dt_channel_data may not initialize that structure fully, so a
    garbage value is used for prescale if the optional "qcom,pre-scaling" is
    not defined in DT. adc5_read_raw then uses this as an array index,
    generating a crash that looks like this:
    
    [    6.683186] Unable to handle kernel paging request at virtual address ffffff90e78c7964
    Call trace:
    qcom_vadc_scale_code_voltage_factor+0x74/0x104
    qcom_vadc_scale_hw_calib_die_temp+0x20/0x60
    qcom_adc5_hw_scale+0x78/0xa4
    adc5_read_raw+0x3d0/0x65c
    iio_channel_read+0x240/0x30c
    iio_read_channel_processed+0x10c/0x150
    qpnp_tm_get_temp+0xc0/0x40c
    of_thermal_get_temp+0x7c/0x98
    thermal_zone_get_temp+0xac/0xd8
    thermal_zone_device_update+0xc0/0x38c
    qpnp_tm_probe+0x624/0x81c
    platform_drv_probe+0xe4/0x11c
    really_probe+0x188/0x3fc
    driver_probe_device+0xb8/0x188
    __device_attach_driver+0x114/0x180
    bus_for_each_drv+0xd8/0x118
    __device_attach+0x180/0x27c
    device_initial_probe+0x20/0x2c
    bus_probe_device+0x78/0x124
    deferred_probe_work_func+0xfc/0x138
    process_one_work+0x3d8/0x8b0
    process_scheduled_works+0x48/0x6c
    worker_thread+0x488/0x7cc
    kthread+0x24c/0x264
    ret_from_fork+0x10/0x18
    
    Unfortunately, when I went to add the initializer for this and tried to
    boot it, my machine shut down immediately, complaining that it was
    hotter than the sun. It appears that adc5_chans_pmic and adc5_chans_rev2
    were initializing prescale_index as if it were directly a divisor,
    rather than the index into adc5_prescale_ratios that it is.
    
    Fix the uninitialized value, and change the static initialization to use
    indices into adc5_prescale_ratios.
    Signed-off-by: default avatarEvan Green <evgreen@chromium.org>
    Reviewed-by: default avatarMatthias Kaehlcke <mka@chromium.org>
    Cc: <Stable@vger.kernel.org>
    Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
    db23d887
qcom-spmi-adc5.c 20.4 KB