Messages in this thread | | | Date | Mon, 19 Mar 2012 10:08:44 +0100 | From | Lars-Peter Clausen <> | Subject | Re: [PATCH v3 1/2] regulator: pcf50633: Don't write to reserved bits of AUTO output voltage select register |
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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> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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