linux-kernel - Re: [PATCH V5 3/3] soc/tegra: pmc: Add support for IO pads power state and voltage

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Message-ID: <573DE19C.8090704@nvidia.com>
Date:	Thu, 19 May 2016 16:54:04 +0100
From:	Jon Hunter <jonathanh@...dia.com>
To:	Laxman Dewangan <ldewangan@...dia.com>, <thierry.reding@...il.com>,
	<airlied@...ux.ie>, <swarren@...dotorg.org>
CC:	<gnurou@...il.com>, <dri-devel@...ts.freedesktop.org>,
	<linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH V5 3/3] soc/tegra: pmc: Add support for IO pads power
 state and voltage


On 12/05/16 13:21, Laxman Dewangan wrote:
> The IO pins of Tegra SoCs are grouped for common control of IO
> interface like setting voltage signal levels and power state of
> the interface. The group is generally referred as IO pads. The
> power state and voltage control of IO pins can be done at IO pads
> level.
> 
> Tegra generation SoC supports the power down of IO pads when it
> is not used even in the active state of system. This saves power
> from that IO interface. Also it supports multiple voltage level
> in IO pins for interfacing on some of pads. The IO pad voltage is
> automatically detected till T124, hence SW need not to configure
> this. But from T210, the automatically detection logic has been
> removed, hence SW need to explicitly set the IO pad voltage into
> IO pad configuration registers.
> 
> Add support to set the power states and voltage level of the IO pads
> from client driver. The implementation for the APIs are in generic
> which is applicable for all generation os Tegra SoC.
> 
> IO pads ID and information of bit field for power state and voltage
> level controls are added for Tegra124, Tegra132 and Tegra210. The SOR
> driver is modified to use the new APIs.
> 
> Signed-off-by: Laxman Dewangan <ldewangan@...dia.com>
> 
> ---
> Changes from V1:
> This is reworked on earlier path to have separation between IO rails and
> io pads and add power state and voltage control APIs in single call.
> 
> Changes from V2:
> - Remove the tegra_io_rail_power_off/on() apis and change client (sor) driver
> to use the new APIs for IO pad power.
> - Remove the TEGRA_IO_RAIL_ macros.
> 
> Changes from V3:
> - Make all pad_id/io_pad_id to id.
> - tegra_io_pad_ -> tegra_io_pads
> - dpd_bit -> bit, pwr_mask/bit to mask/bit.
> - Rename function to tegra_io_pads_{set,get}_voltage_config
> - Make the io pad tables common for all SoC.
> - Make io_pads enums.
> - Add enums for voltage.
> 
> Changes from V4:
> - IO_PAD->IO_PADS
> - TEGRA_IO_PADS_POWER_SOURCE_ -> TEGRA_IO_PADS_VCONF_
> ---
>  drivers/gpu/drm/tegra/sor.c |   8 +-
>  drivers/soc/tegra/pmc.c     | 221 ++++++++++++++++++++++++++++++++++++++------
>  include/soc/tegra/pmc.h     | 132 ++++++++++++++++++--------
>  3 files changed, 294 insertions(+), 67 deletions(-)

[snip]

> +static int tegra_io_pads_to_voltage_bit(const struct tegra_pmc_soc *soc,
> +					enum tegra_io_pads id)
> +{
> +	/* T210 only supports io-pad voltage config bit */
> +	if (soc->io_pads_soc_mask != TEGRA_IO_PADS_T210)
>  		return -EINVAL;

If this is only supported for Tegra210, should these voltage functions
be dependent on CONFIG_ARCH_TEGRA_210_SOC? If so, then I am also
wondering if we should bother having the massive look-up table and just
have a smaller table to translate the ID to bit for voltage as you had
in your initial patch? Seems there are few io-pads that support the
voltage configuration.

+#define TEGRA_IO_RAIL_VOLTAGE(_io_rail, _pos)		\
+{							\
+	.io_rail_id = TEGRA_IO_RAIL_##_io_rail,		\
+	.bit_position = _pos,				\
+}
+
+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),
+};

Otherwise, looks fine to me.

Cheers
Jon

--
nvpublic