linux-kernel - Re: [RFC PATCH 10/12] arm/tegra: Add device tree support to pinmux driver

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Date:	Mon, 15 Aug 2011 21:07:17 +0100
From:	Jamie Iles <jamie@...ieiles.com>
To:	Stephen Warren <swarren@...dia.com>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Colin Cross <ccross@...roid.com>,
	Erik Gilling <konkers@...roid.com>,
	Olof Johansson <olof@...om.net>,
	Russell King <linux@....linux.org.uk>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 10/12] arm/tegra: Add device tree support to pinmux
 driver

Hi Stephen,

On Fri, Aug 12, 2011 at 04:54:55PM -0600, Stephen Warren wrote:
> Signed-off-by: Stephen Warren <swarren@...dia.com>
> ---
>  arch/arm/mach-tegra/pinmux.c |  115 ++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 115 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/mach-tegra/pinmux.c b/arch/arm/mach-tegra/pinmux.c
> index 05fa1a3..33246c2 100644
> --- a/arch/arm/mach-tegra/pinmux.c
> +++ b/arch/arm/mach-tegra/pinmux.c
> @@ -20,6 +20,7 @@
>  #include <linux/errno.h>
>  #include <linux/spinlock.h>
>  #include <linux/io.h>
> +#include <linux/of.h>
>  #include <linux/platform_device.h>
>  
>  #include <mach/iomap.h>
> @@ -147,6 +148,41 @@ static const char *func_name(enum tegra_mux_func func)
>  	return tegra_mux_names[func];
>  }
>  
[...]
>  
>  static const char *tri_name(unsigned long val)
>  {
> @@ -666,15 +702,94 @@ void tegra_pinmux_config_pullupdown_table(const struct tegra_pingroup_config *co
>  	}
>  }
>  
> +#ifdef CONFIG_OF
> +static void __init tegra_pinmux_probe_dt(struct platform_device *pdev)
> +{
> +	int pg;
> +
> +	for (pg = 0; pg < TEGRA_MAX_PINGROUP; pg++) {
> +		const char *pg_name = pingroup_name(pg);
> +		struct tegra_pingroup_config config;
> +		struct device_node *pg_node;
> +		int ret;
> +		const char *s;
> +
> +		pg_node = of_find_child_node_by_name(pdev->dev.of_node,
> +						     pg_name);
> +		if (pg_node == NULL)
> +			continue;
> +
> +		config.pingroup = pg;
> +
> +		ret = of_property_read_string(pg_node, "nvidia,function", &s);
> +		if (ret < 0) {
> +			dev_err(&pdev->dev,
> +				"%s: Missing property nvidia,function\n",
> +				pg_name);
> +			continue;
> +		}
> +		ret = func_enum(s, &config.func);
> +		if (ret < 0) {
> +			dev_err(&pdev->dev,
> +				"%s: Invalid nvidia,function value %s\n",
> +				pg_name, s);
> +			continue;
> +		}
> +
> +		ret = of_property_read_string(pg_node, "nvidia,pull", &s);
> +		if (ret >= 0) {
> +			if (!strcmp(s, "up"))
> +				config.pupd = TEGRA_PUPD_PULL_UP;
> +			else if (!strcmp(s, "down"))
> +				config.pupd = TEGRA_PUPD_PULL_DOWN;
> +			else if (!strcmp(s, "normal"))
> +				config.pupd = TEGRA_PUPD_NORMAL;
> +			else {
> +				dev_err(&pdev->dev,
> +					"%s: Invalid nvidia,pull value %s\n",
> +					pg_name, s);
> +				continue;
> +			}
> +		} else
> +			config.pupd = TEGRA_PUPD_NORMAL;
> +
> +		if (of_find_property(pg_node, "nvidia,tristate", NULL))
> +			config.tristate = TEGRA_TRI_TRISTATE;
> +		else
> +			config.tristate = TEGRA_TRI_NORMAL;
> +
> +		dev_err(&pdev->dev, "%s: func %d (%s) pull %d tri %d\n",
> +			pg_name, config.func, func_name(config.func),
> +			config.pupd, config.tristate);
> +
> +		tegra_pinmux_config_pingroup(&config);
> +
> +		of_node_put(pg_node);
> +	}
> +}

I need to implement DT muxing configuration for my platform, and I believe 
that what you have here would work fine for me too, and to avoid duplicating 
the same thing, I wonder if this could be a little more generic.

So if the platform specific pinmux driver called the pinmux parser with a 
callback for a pingroup configuration function then this wouldn't need the 
nvidia specific properties.  I'd envisage the setup callback to be something 
like:

	int pingroup_configure(const char *name, unsigned long flags);

where the flags would be a bitmask of properties, so:

	PINMUX_F_TRISTATE
	PINMUX_F_PUPD
	etc

which would map to pinmux,tristate properties etc.  The tegra (or 
picoxcell...) specific driver would then map any regs and setup the 
pinmux tables and call the parser loop with the correct callback.  This 
would require looping over the child nodes as we've discussed before, 
and the decoding of the func_enum in the nvidia driver, but I think 
that's okay.

Jamie
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