linux-kernel - Re: [PATCH 2/2] power: supply: Add bd718(15/28/78) charger driver

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Message-ID: <20250820180523.170acbea@akair>
Date: Wed, 20 Aug 2025 18:05:23 +0200
From: Andreas Kemnade <andreas@...nade.info>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, Lee Jones <lee@...nel.org>,
 Sebastian Reichel <sre@...nel.org>, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org
Subject: Re: [PATCH 2/2] power: supply: Add bd718(15/28/78) charger driver

Am Mon, 18 Aug 2025 12:32:43 +0300
schrieb Matti Vaittinen <mazziesaccount@...il.com>:

> > Kobo kernels have these tables as part of the driver, the right one is
> > selected via an index in the NTX_HWCONFIG blob provided by the
> > bootloader to the kernel. So that is not necessarily a problem. It
> > could be translated into dt.
> > 
> > static int ocv_table_28_PR284983N[23] = {
> >          //4200000, 4162288, 4110762, 4066502, 4025265, 3988454, 3955695, 3926323, 3900244, 3876035, 3834038, 3809386, 3794093, 3782718, 3774483, 3768044, 3748158, 3728750, 3704388, 3675577, 3650676, 3463852, 2768530
> >          4200000, 4166349, 4114949, 4072016, 4031575, 3995353, 3963956, 3935650, 3910161, 3883395, 3845310, 3817535, 3801354, 3789708, 3781393, 3774994, 3765230, 3749035, 3726707, 3699147, 3671953, 3607301, 3148394
> > };
> > 
> > static int vdr_table_h_28_PR284983N[23] = {
> >          //100, 100, 101, 101, 102, 102, 103, 103, 104, 104, 105, 106, 106, 107, 107, 108, 108, 109, 110, 112, 124, 157, 786
> >          100, 100, 101, 102, 102, 105, 106, 107, 112, 108, 108, 105, 105, 108, 110, 110, 110, 111, 112, 114, 120, 131, 620
> > };
> > 
> > static int vdr_table_m_28_PR284983N[23] = {
> >          //100, 100, 101, 101, 102, 102, 103, 103, 104, 104, 105, 102, 100, 100, 102, 103, 103, 105, 108, 112, 124, 157, 586
> >          100, 100, 103, 106, 110, 114, 115, 119, 122, 122, 115, 113, 112, 114, 117, 124, 126, 123, 122, 126, 140, 156, 558
> > };
> > 
> > static int vdr_table_l_28_PR284983N[23] = {
> >          //100, 100, 103, 105, 110, 110, 113, 112, 112, 112, 105, 110, 110, 111, 122, 131, 138, 143, 150, 166, 242, 354, 357
> >          100, 100, 105, 110, 114, 117, 121, 125, 126, 122, 116, 114, 115, 118, 124, 132, 140, 148, 156, 170, 210, 355, 579
> > };
> > 
> > static int vdr_table_vl_28_PR284983N[23] = {
> >          //100, 100, 103, 106, 108, 111, 114, 117, 118, 115, 108, 106, 108, 113, 115, 114, 118, 125, 144, 159, 204, 361, 874
> >          100, 100, 109, 115, 118, 123, 127, 130, 140, 139, 134, 130, 128, 138, 140, 150, 154, 164, 178, 204, 271, 362, 352
> > };  
> 
> Oh, good. If we can get the right battery parameters from the vendor 
> driver, then the main problem gets solved. Although, multiple sets of 
> different VDR tables probably means, that there are variants with 
> different types of battery out there. I assume the bootloader can 
> somehow detect the battery type to provide the correct blob?

Historically the Kobo devices ship said HWCONFIG blob apparently to use
the same kernel on multiple devices, then devicetree was invented and
used what was available. There is then a 
                switch(gptHWCFG->m_val.bBattery) {
...
                                ocv_table_default =
                                ocv_table_28_PR284983N;



So that all only means there
are several different batteries amoung the devices supported by that
kernel. From my guts feeling I wonder if the is_relaxed stuff is
properly working and I wonder whether a Kalman filter would give better
results, but that is all something for the future.

Regards,
Andreas