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SubjectRe: [PATCH v3] clk: respect the clock dependencies in of_clk_init
Hi Mike,

On 24/02/2014 19:10, Gregory CLEMENT wrote:
> Until now the clock providers were initialized in the order found in
> the device tree. This led to have the dependencies between the clocks
> not respected: children clocks could be initialized before their
> parent clocks.
>
> Instead of forcing each platform to manage its own initialization order,
> this patch adds this work inside the framework itself.
>
> Using the data of the device tree the of_clk_init function now delayed
> the initialization of a clock provider if its parent provider was not
> ready yet.
>
> The strict dependency check (all parents of a given clk must be
> initialized) was added by Boris BREZILLON

Are you ok with this version?
Will you take it for 3.15?
Or maybe you expected that it will be part of a pull request?

However as it is modifying the core of the framework I thought that you
would take it and apply yourself.

Thanks,

Gregory

>
> Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
> Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com>
> ---
> Mike,
>
> This patch depend on the patch "clk: return probe defer when DT clock
> not yet ready": http://article.gmane.org/gmane.linux.kernel/1643466
>
> If for any reason you don't want to take it, then I will write a new
> version closer to the v2 for the parent_ready() function.
>
> I have taken into account all the remarks from Tomasz.
>
> Thanks,
>
> Changelog:
> v2->v3:
>
> - added the SoB flag of Boris
> - used of_clk_get(np, i) in the parent_ready() function.
> - simplified the loops to manage the order dependencies in of_clk_init()
>
> v1 -> v2:
> Merged the strict dependency check from Boris.
>
>
> drivers/clk/clk.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 79 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 32d84e921b23..3a07f8ac2e11 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -2526,24 +2526,99 @@ const char *of_clk_get_parent_name(struct device_node *np, int index)
> }
> EXPORT_SYMBOL_GPL(of_clk_get_parent_name);
>
> +struct clock_provider {
> + of_clk_init_cb_t clk_init_cb;
> + struct device_node *np;
> + struct list_head node;
> +};
> +
> +static LIST_HEAD(clk_provider_list);
> +
> +/*
> + * This function looks for a parent clock. If there is one, then it
> + * checks that the provider for this parent clock was initialized, in
> + * this case the parent clock will be ready.
> + */
> +static int parent_ready(struct device_node *np)
> +{
> + int i = 0;
> +
> + while (true) {
> + struct clk *clk = of_clk_get(np, i);
> +
> + /* this parent is ready we can check the next one */
> + if (!IS_ERR(clk)) {
> + clk_put(clk);
> + i++;
> + continue;
> + }
> +
> + /* at least one parent is not ready, we exit now */
> + if (PTR_ERR(clk) == -EPROBE_DEFER)
> + return 0;
> +
> + /*
> + * Here we make assumption that the device tree is
> + * written correctly. So an error means that there is
> + * no more parent. As we didn't exit yet, then the
> + * previous parent are ready. If there is no clock
> + * parent, no need to wait for them, then we can
> + * consider their absence as being ready
> + */
> + return 1;
> + }
> +}
> +
> /**
> * of_clk_init() - Scan and init clock providers from the DT
> * @matches: array of compatible values and init functions for providers.
> *
> - * This function scans the device tree for matching clock providers and
> - * calls their initialization functions
> + * This function scans the device tree for matching clock providers
> + * and calls their initialization functions. It also do it by trying
> + * to follow the dependencies.
> */
> void __init of_clk_init(const struct of_device_id *matches)
> {
> const struct of_device_id *match;
> struct device_node *np;
> + struct clock_provider *clk_provider, *next;
> + bool is_init_done;
> + bool force = false;
>
> if (!matches)
> matches = &__clk_of_table;
>
> + /* First prepare the list of the clocks providers */
> for_each_matching_node_and_match(np, matches, &match) {
> - of_clk_init_cb_t clk_init_cb = match->data;
> - clk_init_cb(np);
> + struct clock_provider *parent =
> + kzalloc(sizeof(struct clock_provider), GFP_KERNEL);
> +
> + parent->clk_init_cb = match->data;
> + parent->np = np;
> + list_add(&parent->node, &clk_provider_list);
> + }
> +
> + while (!list_empty(&clk_provider_list)) {
> + is_init_done = false;
> + list_for_each_entry_safe(clk_provider, next,
> + &clk_provider_list, node) {
> + if (force || parent_ready(clk_provider->np)) {
> + clk_provider->clk_init_cb(clk_provider->np);
> + list_del(&clk_provider->node);
> + kfree(clk_provider);
> + is_init_done = true;
> + }
> + }
> +
> + /*
> + * We didn't managed to initialize any of the
> + * remaining providers during the last loop, so now we
> + * initialize all the remaining ones unconditionally
> + * in case the clock parent was not mandatory
> + */
> + if (!is_init_done)
> + force = true;
> +
> }
> }
> #endif
>


--
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com


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