linux-kernel - Re: [PATCH v2 1/4] power: supply: add support for max77759 fuel gauge

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Message-ID: <ocx5n42h25ztwo5twlir5zoajavpcxce2ra5jjyl6ae4qg6c3e@akhc3dylsprm>
Date: Wed, 15 Jan 2025 22:30:16 +0100
From: Sebastian Reichel <sebastian.reichel@...labora.com>
To: t.antoine@...ouvain.be
Cc: Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Dimitri Fedrau <dima.fedrau@...il.com>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>, Peter Griffin <peter.griffin@...aro.org>, 
	Alim Akhtar <alim.akhtar@...sung.com>, André Draszik <andre.draszik@...aro.org>, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v2 1/4] power: supply: add support for max77759 fuel gauge

Hi,

On Thu, Jan 02, 2025 at 12:15:03PM +0100, Thomas Antoine via B4 Relay wrote:
> From: Thomas Antoine <t.antoine@...ouvain.be>
> 
> The interface of the Maxim max77759 fuel gauge has a lot of common with the
> Maxim max1720x. The major difference is the lack of non-volatile memory
> slave address. No slave is available at address 0xb of the i2c bus, which
> is coherent with the following driver from google: line 5836 disables
> non-volatile memory for m5 gauge.
> 
> Link: https://android.googlesource.com/kernel/google-modules/bms/+/1a68c36bef474573cc8629cc1d121eb6a81ab68c/max1720x_battery.c
> 
> Other differences include the lack of V_BATT register to read the battery
> level and a difference in the way to identify the chip (the same register
> is used but not the same mask).
> 
> Add support for the max77759 by allowing to use the non-volatile
> memory or not based on the chip. Also add the V_CELL regsister as a
> fallback to read voltage value in the case where read of V_BATT fails.
> 
> The cast is necessary to avoid an overflow when the value of the register
> is above 54975 (equivalent to a voltage around 4.29 V).
> 
> The regmap of the max77759 will lead the read to fail for V_BATT and to
> correctly use V_CELL instead. This regmap was proposed by André Draszik in
> 
> Link: https://lore.kernel.org/all/d1bade77b5281c1de6b2ddcb4dbbd033e455a116.camel@linaro.org/
> 
> Signed-off-by: Thomas Antoine <t.antoine@...ouvain.be>
> ---

Please add output from to the cover letter to allow easily verifying
that all values are correctly scaled.

./tools/testing/selftests/power_supply/test_power_supply_properties.sh

> +static const struct regmap_access_table max77759_write_table = {
> +	.yes_ranges = max77759_registers,
> +	.n_yes_ranges = ARRAY_SIZE(max77759_registers),
> +	.no_ranges = max77759_ro_registers,
> +	.n_no_ranges = ARRAY_SIZE(max77759_ro_registers),
> +};

Drop the yes_range from the write table. It is wrong and confusing.

Greetings,

-- Sebastian

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