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    SubjectRe: [PATCH v3 1/2] regulator: pcf50633: Don't write to reserved bits of AUTO output voltage select register
    On 03/19/2012 03:55 AM, Axel Lin wrote:
    > The datasheet says 00000000 to 00101110 are reserved, and the min value of the
    > voltage setting is 1.8 V.
    > Thus don't write 0 to AUTO output voltage select register (address 1Ah).
    >
    > Table 50. AUTOOUT - AUTO output voltage select register (address 1Ah) bit description[1]
    > Bit Symbol Access Description
    > 7:0 auto_out R/W VO(prog) = 0.625 + auto_out × 0.025 V
    > eg. 00000000 to 00101110: reserved
    > 00101111: 1.8 V (min)
    > 01010011: 2.7 V
    > 01101010: 3.275 V
    > 01101011: 3.300 V
    > 01101100: 3.325 V
    > 01111111 : 3.800 V (max)
    > ..... .....
    > 11111110 : 3.800 V
    > 11111111 : 3.800 V
    >
    > This patch also fixes a bug in pcf50633_regulator_list_voltage:
    > In regulator core _regulator_do_set_voltage function:
    >
    > if (rdev->desc->ops->set_voltage) {
    > ret = rdev->desc->ops->set_voltage(rdev, min_uV, max_uV,
    > &selector);
    >
    > if (rdev->desc->ops->list_voltage)
    > selector = rdev->desc->ops->list_voltage(rdev,
    > selector);
    > else
    > selector = -1;
    >
    > The list_voltage call here takes the selector got from set_voltage callback.
    > Thus adding 0x2f to the index in pcf50633_regulator_list_voltage looks wrong to me.
    >
    > e.g.
    > If min_uV < 1.8V, pcf50633_regulator_set_voltage sets 0 to selector.
    > For this case, adding 0x2f to the index in pcf50633_regulator_list_voltage is correct.
    > However, if min_uV == 1.8V, pcf50633_regulator_set_voltage sets 0x2f to selector.
    > Adding 0x2f to the index in pcf50633_regulator_list_voltage in this case is wrong.
    >
    > What this patch does is:
    > The minimal voltage setting for AUTOOUT is 0x2f.
    > Thus for the case min_uV < 1.8, set the voltage setting to 1.8V by writting
    > 0x2f to AUTOOUT register and set selector = 0x2f.
    > So we don't write the rserved range to AUTOOUT register.
    > Which means the possible range of AUTOOUT register value is 0x2f ~ 0xff.
    >
    > We have no problem in regulator_get_voltage.
    > Since we won't write 0~0x2e to AUTOOUT register, we have no problem converting
    > the bits we read to voltage. The equation in auto_voltage_value works fine.
    >
    > For list_voltage, we need to take into account the case selector is 0 ~ 0x2e
    > because the regulator core assumes the selector is starting from 0.
    > This patch returns 0 for the cases selector is 0 ~ 0x2e, which means
    > "this selector code can't be used on this system".
    >
    > The regulator core iterates from 0 to n_voltages to find the small voltage
    > in the specific range. The n_voltages settings for AUTOOUT should be 128 now,
    > including the reserved range of AUTOOUT.
    >
    > Signed-off-by: Axel Lin <axel.lin@gmail.com>

    Acked-by: Lars-Peter Clausen <lars@metafoo.de>
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