linux-kernel - Re: [PATCH V2 2/2] pinctrl: tegra: Add driver to configure voltage and power of io pads

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Date:   Mon, 21 Nov 2016 15:06:05 +0530
From:   Laxman Dewangan <ldewangan@...dia.com>
To:     Jon Hunter <jonathanh@...dia.com>, <linus.walleij@...aro.org>,
        <robh+dt@...nel.org>, <mark.rutland@....com>,
        <swarren@...dotorg.org>, <thierry.reding@...il.com>
CC:     <gnurou@...il.com>, <yamada.masahiro@...ionext.com>,
        <linux-gpio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 2/2] pinctrl: tegra: Add driver to configure voltage
 and power of io pads


Hi Jon,
I will update the patch per your comment.
Here is answer for some of the query.

Thanks,
Laxman


On Tuesday 15 November 2016 08:37 PM, Jon Hunter wrote:
> On 09/11/16 13:06, Laxman Dewangan wrote:
>> +/**
>> + * Macro for 1.8V, keep 200mV as tolerance for deciding that
>> + * IO pads should be set for 3.3V (high voltage) or 1.8V.
>> + */
>> +#define TEGRA_IO_PAD_1800000UV_UPPER_LIMIT 2000000
> Is there a reference we could add for the source of this information?

I had a discussion with the ASIC on this and as per them
     1.8 V nominal is (1.62V, 1.98V)
     3.3 V nominal is (2.97V,3.63V)

I am working with them to update the TRM document but we can assume that 
this information will be there in TRM.

>> +	const struct pinctrl_pin_desc *pins_desc;
>> +	int num_pins_desc;
>> +};
>> +
>> +struct tegra_io_pads_regulator_info {
>> +	struct device *dev;
>> +	const struct tegra_io_pads_cfg_info *pads_cfg;
>> +	struct regulator *regulator;
>> +	struct notifier_block regulator_nb;
>> +};
> Is this struct necessary? Seems to be a lot of duplicated information
> from the other structs. Why not add the regulator and regulator_nb to
> the main struct? OK, not all io_pads have a regulator but you are only
> saving one pointer.
Yes, some of IO pads support multi-voltage.


>
> +		if ((vdata->old_uV > TEGRA_IO_PAD_1800000UV_UPPER_LIMIT) &&
> +		    (vdata->min_uV <= TEGRA_IO_PAD_1800000UV_UPPER_LIMIT))
> +			break;
> The data-sheet for Tegra210 only lists 1.8V or 3.3V as supported
> options. Do we need to support a range? Or does the h/w support a range
> of voltages? I am just wondering why we cannot check explicitly for 1.8V
> or 3.3V and treat anything else as an error.

Two voltage level, not range.