| Message ID | 19d537f9920cae5fa849b649e5bc42ba0b8e52f8.1759824376.git.mazziesaccount@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | Support ROHM BD72720 PMIC | expand |
Hi Matti, thanks for your patch! On Tue, Oct 7, 2025 at 10:33 AM Matti Vaittinen <mazziesaccount@gmail.com> wrote: > The BD72720 PMIC has a battery charger + coulomb counter block. These > can be used to manage charging of a lithium-ion battery and to do fuel > gauging. > > ROHM has developed a so called "zero-correction" -algotihm to improve algorithm? > the fuel-gauging accuracy close to the point where battery is depleted. > This relies on battery specific "VDR" tables, which are measured from > the battery, and which describe the voltage drop rate. More thorough > explanation about the "zero correction" and "VDR" parameters is here: > https://lore.kernel.org/all/676253b9-ff69-7891-1f26-a8b5bb5a421b@fi.rohmeurope.com/ > > Document the VDR zero-correction specific battery properties used by the > BD72720 and some other ROHM chargers. > > Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> > The parameters are describing the battery voltage drop rates - so they > are properties of the battery, not the charger. Thus they do not belong > in the charger node. Right! > The right place for them is the battery node, which is described by the > generic "battery.yaml". I was not comfortable with adding these > properties to the generic battery.yaml because they are: > - Meaningful only for those charger drivers which have the VDR > algorithm implemented. (And even though the algorithm is not charger > specific, AFAICS, it is currently only used by some ROHM PMIC > drivers). > - Technique of measuring the VDR tables for a battery is not widely > known. AFAICS, only folks at ROHM are measuring those for some > customer products. We do have those tables available for some of the > products though (Kobo?). It would be sad if we later on have to convert it to a standard property because it turns out to be wider used than we know. But I buy your reasoning! > +properties: > + rohm,voltage-vdr-thresh-microvolt: > + description: Threshold for starting the VDR correction > + > + rohm,volt-drop-soc: > + description: Table of capacity values matching the values in VDR tables. > + $ref: /schemas/types.yaml#/definitions/uint32-array Which unit is this? Seems to be capacity in % *10? > + rohm,volt-drop-high-temp-microvolt: > + description: VDR table for high temperature > + > + rohm,volt-drop-normal-temp-microvolt: > + description: VDR table for normal temperature > + > + rohm,volt-drop-low-temp-microvolt: > + description: VDR table for low temperature > + > + rohm,volt-drop-very-low-temp-microvolt: > + description: VDR table for very low temperature Doesn't the four last properties require to be defined as uint32-array? > + rohm,volt-drop-soc = <1000 1000 950 900 850 800 750 700 650 600 550 500 > + 450 400 350 300 250 200 150 100 50 00 (-50)>; This one makes a lot of sense. > + rohm,volt-drop-high-temp-microvolt = <100 100 102 104 106 109 114 124 > + 117 107 107 109 112 116 117 108 109 109 108 109 122 126 130>; > + > + rohm,volt-drop-normal-temp-microvolt = <100 100 102 105 98 100 105 102 > + 101 99 98 100 103 105 109 117 111 109 110 114 128 141 154>; > + > + rohm,volt-drop-low-temp-microvolt = <100 100 98 107 112 114 118 118 112 > + 108 108 110 111 113 117 123 131 144 157 181 220 283 399>; > + > + rohm,volt-drop-very-low-temp-microvolt = <86 86 105 109 114 110 115 115 > + 110 108 110 112 114 118 124 134 136 160 177 201 241 322 403>; I would have expected something like this, to avoid the a bit fuzzy definitions of high, normal, low and very low temperature either: Provide an array of temperatures in millicentigrades (I just guessed these temperatures, you will know the real ones!): rohm,vold-drop-temperatures-millicelsius = <500, 250, 100, (-50)>; rohm,volt-drop-microvolt-0 = <...>; rohm,volt-drop-microvolt-1 = <...>; rohm,volt-drop-microvolt-2 = <...>; rohm,volt-drop-microvolt-3 = <...>; Where each array correspond to the temperature, or if you wanna go all-out custom: rohm,volt-drop-50-celsius-microvolt = <...>; (...) So we get the actual temperature in there one way or the other. > + rohm,voltage-vdr-thresh-microvolt = <4150000>; This property seems to be missing from the bindings? Yours, Linus Walleij
On 13/10/2025 15:45, Linus Walleij wrote: > Hi Matti, > > thanks for your patch! > > On Tue, Oct 7, 2025 at 10:33 AM Matti Vaittinen > <mazziesaccount@gmail.com> wrote: > >> The BD72720 PMIC has a battery charger + coulomb counter block. These >> can be used to manage charging of a lithium-ion battery and to do fuel >> gauging. >> >> ROHM has developed a so called "zero-correction" -algotihm to improve > > algorithm? Indeed :) > >> the fuel-gauging accuracy close to the point where battery is depleted. >> This relies on battery specific "VDR" tables, which are measured from >> the battery, and which describe the voltage drop rate. More thorough >> explanation about the "zero correction" and "VDR" parameters is here: >> https://lore.kernel.org/all/676253b9-ff69-7891-1f26-a8b5bb5a421b@fi.rohmeurope.com/ >> >> Document the VDR zero-correction specific battery properties used by the >> BD72720 and some other ROHM chargers. >> >> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> > >> The parameters are describing the battery voltage drop rates - so they >> are properties of the battery, not the charger. Thus they do not belong >> in the charger node. > > Right! > >> The right place for them is the battery node, which is described by the >> generic "battery.yaml". I was not comfortable with adding these >> properties to the generic battery.yaml because they are: >> - Meaningful only for those charger drivers which have the VDR >> algorithm implemented. (And even though the algorithm is not charger >> specific, AFAICS, it is currently only used by some ROHM PMIC >> drivers). >> - Technique of measuring the VDR tables for a battery is not widely >> known. AFAICS, only folks at ROHM are measuring those for some >> customer products. We do have those tables available for some of the >> products though (Kobo?). > > It would be sad if we later on have to convert it to a standard property > because it turns out to be wider used than we know. > > But I buy your reasoning! > >> +properties: >> + rohm,voltage-vdr-thresh-microvolt: >> + description: Threshold for starting the VDR correction >> + >> + rohm,volt-drop-soc: >> + description: Table of capacity values matching the values in VDR tables. >> + $ref: /schemas/types.yaml#/definitions/uint32-array > > Which unit is this? Seems to be capacity in % *10? Ah, right. Should've documented this! Thanks. >> + rohm,volt-drop-high-temp-microvolt: >> + description: VDR table for high temperature >> + >> + rohm,volt-drop-normal-temp-microvolt: >> + description: VDR table for normal temperature >> + >> + rohm,volt-drop-low-temp-microvolt: >> + description: VDR table for low temperature >> + >> + rohm,volt-drop-very-low-temp-microvolt: >> + description: VDR table for very low temperature > > Doesn't the four last properties require to be defined as uint32-array? I have been under impression that the "-microvolt" ending suffices, but I may be wrong. At last the 'make dt_binding_check' didn't give me a shout. > >> + rohm,volt-drop-soc = <1000 1000 950 900 850 800 750 700 650 600 550 500 >> + 450 400 350 300 250 200 150 100 50 00 (-50)>; > > This one makes a lot of sense. > >> + rohm,volt-drop-high-temp-microvolt = <100 100 102 104 106 109 114 124 >> + 117 107 107 109 112 116 117 108 109 109 108 109 122 126 130>; >> + >> + rohm,volt-drop-normal-temp-microvolt = <100 100 102 105 98 100 105 102 >> + 101 99 98 100 103 105 109 117 111 109 110 114 128 141 154>; >> + >> + rohm,volt-drop-low-temp-microvolt = <100 100 98 107 112 114 118 118 112 >> + 108 108 110 111 113 117 123 131 144 157 181 220 283 399>; >> + >> + rohm,volt-drop-very-low-temp-microvolt = <86 86 105 109 114 110 115 115 >> + 110 108 110 112 114 118 124 134 136 160 177 201 241 322 403>; > > I would have expected something like this, to avoid the a bit fuzzy definitions > of high, normal, low and very low temperature either: > > Provide an array of temperatures in millicentigrades (I just guessed > these temperatures, you will know the real ones!): > > rohm,vold-drop-temperatures-millicelsius = <500, 250, 100, (-50)>; > rohm,volt-drop-microvolt-0 = <...>; > rohm,volt-drop-microvolt-1 = <...>; > rohm,volt-drop-microvolt-2 = <...>; > rohm,volt-drop-microvolt-3 = <...>; > > Where each array correspond to the temperature, or if you wanna > go all-out custom: > > rohm,volt-drop-50-celsius-microvolt = <...>; > (...) > > So we get the actual temperature in there one way or the other. I agree. This is a good idea. I'll try one of these :) > >> + rohm,voltage-vdr-thresh-microvolt = <4150000>; > > This property seems to be missing from the bindings? I think it is the first binding in the file :) Yours, -- Matti
On Mon, Oct 13, 2025 at 3:00 PM Matti Vaittinen <mazziesaccount@gmail.com> wrote: > >> + rohm,volt-drop-very-low-temp-microvolt: > >> + description: VDR table for very low temperature > > > > Doesn't the four last properties require to be defined as uint32-array? > > I have been under impression that the "-microvolt" ending suffices, but > I may be wrong. At last the 'make dt_binding_check' didn't give me a shout. Ah you're right, I tend to forget about all the magic Rob has put into dtsschema. > >> + rohm,voltage-vdr-thresh-microvolt = <4150000>; > > > > This property seems to be missing from the bindings? > > I think it is the first binding in the file :) Ugh I missed it. Yours, Linus Walleij
diff --git a/Documentation/devicetree/bindings/power/supply/rohm,vdr-battery.yaml b/Documentation/devicetree/bindings/power/supply/rohm,vdr-battery.yaml new file mode 100644 index 000000000000..85611ed050fa --- /dev/null +++ b/Documentation/devicetree/bindings/power/supply/rohm,vdr-battery.yaml @@ -0,0 +1,78 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/power/supply/rohm,vdr-battery.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Battery managed by the BD72720 PMIC + +maintainers: + - Matti Vaittinen <mazziesaccount@gmail.com> + +description: + A battery which has VDR parameters measuerd for ROHM chargers. + +allOf: + - $ref: battery.yaml# + +properties: + rohm,voltage-vdr-thresh-microvolt: + description: Threshold for starting the VDR correction + + rohm,volt-drop-soc: + description: Table of capacity values matching the values in VDR tables. + $ref: /schemas/types.yaml#/definitions/uint32-array + + rohm,volt-drop-high-temp-microvolt: + description: VDR table for high temperature + + rohm,volt-drop-normal-temp-microvolt: + description: VDR table for normal temperature + + rohm,volt-drop-low-temp-microvolt: + description: VDR table for low temperature + + rohm,volt-drop-very-low-temp-microvolt: + description: VDR table for very low temperature + + +additionalProperties: false + +examples: + - | + power { + #address-cells = <1>; + #size-cells = <0>; + + battery: battery { + compatible = "simple-battery"; + + ocv-capacity-celsius = <25>; + ocv-capacity-table-0 = <4200000 100 4184314 100 4140723 95 4099487 90 + 4060656 85 4024350 80 3991121 75 3954379 70 3913265 65 3877821 60 + 3855577 55 3837466 50 3822194 45 3809012 40 3795984 35 3780647 30 + 3760505 25 3741532 20 3718837 15 3696698 10 3690594 5 3581427 0>; + + rohm,volt-drop-soc = <1000 1000 950 900 850 800 750 700 650 600 550 500 + 450 400 350 300 250 200 150 100 50 00 (-50)>; + + rohm,volt-drop-high-temp-microvolt = <100 100 102 104 106 109 114 124 + 117 107 107 109 112 116 117 108 109 109 108 109 122 126 130>; + + rohm,volt-drop-normal-temp-microvolt = <100 100 102 105 98 100 105 102 + 101 99 98 100 103 105 109 117 111 109 110 114 128 141 154>; + + rohm,volt-drop-low-temp-microvolt = <100 100 98 107 112 114 118 118 112 + 108 108 110 111 113 117 123 131 144 157 181 220 283 399>; + + rohm,volt-drop-very-low-temp-microvolt = <86 86 105 109 114 110 115 115 + 110 108 110 112 114 118 124 134 136 160 177 201 241 322 403>; + + rohm,voltage-vdr-thresh-microvolt = <4150000>; + + charge-full-design-microamp-hours = <1799000>; + voltage-max-design-microvolt = <4200000>; + voltage-min-design-microvolt = <3500000>; + degrade-cycle-microamp-hours = <131>; + }; + };
The BD72720 PMIC has a battery charger + coulomb counter block. These can be used to manage charging of a lithium-ion battery and to do fuel gauging. ROHM has developed a so called "zero-correction" -algotihm to improve the fuel-gauging accuracy close to the point where battery is depleted. This relies on battery specific "VDR" tables, which are measured from the battery, and which describe the voltage drop rate. More thorough explanation about the "zero correction" and "VDR" parameters is here: https://lore.kernel.org/all/676253b9-ff69-7891-1f26-a8b5bb5a421b@fi.rohmeurope.com/ Document the VDR zero-correction specific battery properties used by the BD72720 and some other ROHM chargers. Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> --- The parameters are describing the battery voltage drop rates - so they are properties of the battery, not the charger. Thus they do not belong in the charger node. The right place for them is the battery node, which is described by the generic "battery.yaml". I was not comfortable with adding these properties to the generic battery.yaml because they are: - Meaningful only for those charger drivers which have the VDR algorithm implemented. (And even though the algorithm is not charger specific, AFAICS, it is currently only used by some ROHM PMIC drivers). - Technique of measuring the VDR tables for a battery is not widely known. AFAICS, only folks at ROHM are measuring those for some customer products. We do have those tables available for some of the products though (Kobo?). --- .../power/supply/rohm,vdr-battery.yaml | 78 +++++++++++++++++++ 1 file changed, 78 insertions(+) create mode 100644 Documentation/devicetree/bindings/power/supply/rohm,vdr-battery.yaml