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    SubjectRe: [PATCH v2 1/2] regulator: pcf50633: Don't write to reserved bits of AUTO output voltage select register
    On 03/17/2012 01:07 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.
    > It is wrong to do "index += 0x2f" for PCF50633_REGULATOR_AUTO in
    > pcf50633_regulator_list_voltage. The purpose of adding 0x2f to index is because
    > current code return 0 in auto_voltage_bits when millivolts < 1800.
    > For millivolts > 1800, adding 0x2f to index is wrong.
    >

    I think you misunderstood what the current code does. The first usable voltage
    is 1.8V which is equal to a index of of 0x2f. So the driver adds 0x2f to the
    index so that there is not a headroom of 0x2f unusable voltages. So a selector
    of 0 translates to 1.8V, a selector of 1 translates to 1.825V and so on.

    I can see why you'd want to change it to simplify the code, but you also have
    to change the number of voltages for the AUTO regulator to 128.
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