linux-kernel - Re: [PATCH 4/7] soc/tegra: pmc: Add interface to set voltage of IO rails

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Date:	Fri, 15 Apr 2016 10:24:46 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Laxman Dewangan <ldewangan@...dia.com>
Cc:	thierry.reding@...il.com, linus.walleij@...aro.org,
	gnurou@...il.com, robh+dt@...nel.org, mark.rutland@....com,
	jonathanh@...dia.com, linux-tegra@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-gpio@...r.kernel.org
Subject: Re: [PATCH 4/7] soc/tegra: pmc: Add interface to set voltage of IO
 rails

On 04/12/2016 08:56 AM, Laxman Dewangan wrote:
> NVIDIA Tegra210 supports some of the IO interface which can operate
> at 1.8V or 3.3V I/O rail voltage levels. SW needs to configure
> Tegra PMC register to set different voltage level of IO interface based
> on IO rail voltage from power supply i.e. power regulators.
>
> Add APIs to set and get IO rail voltage from the client driver.

> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c

> +static struct tegra_io_rail_voltage_bit_info tegra210_io_rail_voltage_info[] = {
> +	TEGRA_IO_RAIL_VOLTAGE(SDMMC1, 12),
> +	TEGRA_IO_RAIL_VOLTAGE(SDMMC3, 13),
> +	TEGRA_IO_RAIL_VOLTAGE(AUDIO_HV, 18),
> +	TEGRA_IO_RAIL_VOLTAGE(DMIC, 20),
> +	TEGRA_IO_RAIL_VOLTAGE(GPIO, 21),
> +	TEGRA_IO_RAIL_VOLTAGE(SPI_HV, 23),
> +};

That table is likely specific to Tegra210, yet ...

> +static int tegra_io_rail_voltage_get_bit_pos(int io_rail_id)
> +int tegra_io_rail_voltage_set(int io_rail, int val)
> +int tegra_io_rail_voltage_get(int io_rail)

... these functions are all named as if they are generic. Presumably 
they will indeed be needed for the next chip too? How will you prevent 
their use, or turn these functions into no-ops, or return errors, on 
other SoCs?