Messages in this thread | | | Date | Mon, 19 Mar 2012 10:07:42 +0100 | From | Lars-Peter Clausen <> | Subject | Re: [PATCH v2 1/2] regulator: pcf50633: Don't write to reserved bits of AUTO output voltage select register |
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On 03/19/2012 03:53 AM, Axel Lin wrote: > 2012/3/18 Lars-Peter Clausen <lars@metafoo.de>: >> 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 think what I wry to explain is: > 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. >
Ah ok, now I understand what you mean. When the selector parameter to set_voltage was introduced we already had list_voltage adding the 0x2f, so from my point of view list_voltage is correct and the bug is in the commit which introduced the selector parameter to select voltage, that's why I was confused as to why you think there was a bug in list_voltage. But it all makes sense now, thanks.
Luckily the bug is not so critical, since selector is not really used in _regulator_do_set_voltage in this case except for the trace message.
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