linux-kernel - Re: [PATCH V2 6/6] pinctrl: tegra: Add complete device tree support

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Message-ID: <20120322040730.GC840@shlinux2.ap.freescale.net>
Date:	Thu, 22 Mar 2012 12:07:31 +0800
From:	Dong Aisheng <aisheng.dong@...escale.com>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	Dong Aisheng-B29396 <B29396@...escale.com>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linus.walleij@...ricsson.com" <linus.walleij@...ricsson.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"dongas86@...il.com" <dongas86@...il.com>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"thomas.abraham@...aro.org" <thomas.abraham@...aro.org>,
	"tony@...mide.com" <tony@...mide.com>,
	"sjg@...omium.org" <sjg@...omium.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH V2 6/6] pinctrl: tegra: Add complete device tree support

On Thu, Mar 22, 2012 at 12:07:27AM +0800, Stephen Warren wrote:
> On 03/21/2012 03:35 AM, Dong Aisheng wrote:
> > On Wed, Mar 21, 2012 at 01:44:39AM +0800, Stephen Warren wrote:
> >> Implement pinctrl_ops dt_node_to_map() and dt_free_map(). These allow
> >> complete specification of the desired pinmux configuration using device
> >> tree.
> >>
> >> Signed-off-by: Stephen Warren <swarren@...dotorg.org>
> >> ---
> >> v2: Rebase on of_property_for_each_string() API changes.
> >> ---
> > Nice code and a good example to people.
> > 
> > A small suggestion below:
> >> +static int add_map_configs(struct pinctrl_map **map, unsigned *num_maps,
> >> +			   const char *group, unsigned long *configs,
> >> +			   unsigned num_configs)
> >> +{
> >> +	unsigned i = *num_maps;
> >> +	unsigned long *dup_configs;
> >> +	int ret;
> >> +
> >> +	dup_configs = kmemdup(configs, num_configs * sizeof(*dup_configs),
> >> +			      GFP_KERNEL);
> >> +	if (!dup_configs)
> >> +		return -ENOMEM;
> >> +
> >> +	ret = add_map(map, num_maps);
> >> +	if (ret < 0)
> >> +		return ret;
> >> +
> >> +	(*map)[i].type = PIN_MAP_TYPE_CONFIGS_GROUP;
> >
> > It still does not support PIN_MAP_TYPE_CONFIGS_PIN, right?
> 
> Yes.
> 
> This is mainly due to a pinctrl core limitation. The core only supports
> muxing on groups, so even though the Tegra30 HW supports muxing per pin,
> the driver must define a group for each pin. Given that, it's simplest
> just to do all the pin config on those same groups.
> 
> If/when the pinctrl core supports muxing per pin, we can take advantage
> of this within the Tegra pinctrl driver without affecting the binding at
> all.
> 
Yes, reasonable.

> >> +	for_each_child_of_node(np_config, np) {
> >> +		ret = of_property_read_string(np, "nvidia,function", &function);
> >> +		if (ret < 0)
> >> +			function = NULL;
> >> +
> >> +		for (i = 0; i < ARRAY_SIZE(cfg_params); i++) {
> >> +			ret = of_property_read_u32(np, cfg_params[i].property,
> >> +						   &val);
> >> +			if (!ret) {
> >> +				config = TEGRA_PINCONF_PACK(
> >> +						cfg_params[i].param, val);
> >> +				ret = add_config(&configs, &num_configs,
> >> +						 config);
> >> +				if (ret < 0)
> >> +					goto error;
> >> +			}
> >> +		}
> >> +
> >> +		of_property_for_each_string(np, "nvidia,pins", prop, group) {
> >
> > If we calculate out the strings count and allocate corresponding size array, we may not
> > need to keep krealloc the maps and configs array size for each entry.
> > And this may be a little higher efficient.
> 
> That's true. However, it'd require the code to loop once to determine
> how many properties are present and how many entries there are in the
> pin list. Then, loop again to actually construct the mapping table
> array. This is all added complexity that doesn't affect correctness. I'd
> rather get the simple code going first, and then refine it later if
> there turns out to be a performance issue.
> 
Can we use of_property_count_strings?

Regards
Dong Aisheng


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