Messages in this thread | | | Subject | Re: [PATCH v3 2/2] hwmon: ina3221: Read channel input source info from DT | From | Guenter Roeck <> | Date | Sat, 22 Sep 2018 19:07:02 -0700 |
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On 09/22/2018 05:38 PM, Nicolin Chen wrote: > On Sat, Sep 22, 2018 at 04:59:55PM -0700, Guenter Roeck wrote: > >>>>> + /* Disable channels if their inputs are disconnected */ >>>>> + for (i = 0, mask = 0; i < INA3221_NUM_CHANNELS; i++) { >>>>> + if (ina->inputs[i].disconnected) >>>>> + mask |= INA3221_CONFIG_CHx_EN(i); >>>>> + } >>>> >>>> Consequently, you should also _enable_ channels which are not explicitly disabled. >>> >>> The register has enabled all channels by default. So I felt it'd >>> be neat to have disabling code only. My v1 actually had enabling >>> part as well, but I can add it back if you think it'd be better. >>> >>>> This can be tricky since you'll have to distinguish non-DT and DT configuration >>>> and retain the original configuration if no channel configuration data is available >>>> from devicetree. > >>> For non-DT configurations, input->disconnected is always false by >>> default unless someone adds config for it (through platform_data). >>> If regmap_update_bits only does disabling like this version does, >>> non-DT configurations will not get affected since mask = 0. Or if >>> we change it to do both enabling and disabling, regmap_update_bits >>> will still ignore since there's no register value changed, though >>> it won't really hurt even if regmap writes correct configurations >>> to the register. >>> >>> For DT configurations (without channel input source defined), it's >>> like the same as non-DT configurations. As we have platforms only >>> enabled ina3221 via DT while they don't have this new DT binding, >>> the driver has to be backward compatible, so my change only sets >>> input->disconnected=true when a status="disabled" is present, i.e. >>> those platforms are treated as all channels getting enabled until >>> they update their DTs. > >> I think your assumption may be that the chip is always in its reset state >> when Linux is loaded. This is not necessarily the case; it may be >> preconfigured by BIOS or ROMMON, or even by someone using i2cset before >> loading the driver. If you add enable/disable functionality, you can >> not make an assumption about the original state of the chip at probe time; >> you have to read it from the chip itself. > > I see. That made a point. In that case, I think the simplest way > is probably to do software reset before having configurations. > No. If the chip was configured by the BIOS/ROMMON, it is supposed to be that way. We can not just override that.
Guenter
> The "disconnected" here is to describe the physical connection, > not exact the switch control status because a channel could be > connected but disabled. However, a channel would not be enabled > if it's disconnected. So I think it'd be safe to just disable > the disconnected channels here as this version does, meanwhile, > I will add a soft reset to make sure all channels are enabled. > > Thanks > Nicolin >
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