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    SubjectRe: [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@wwwdotorg.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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