Mike,
On Tue, Feb 04, 2014 at 11:59:26PM +0100, 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.
>
> Signed-off-by: Gregory CLEMENT <gregory.clem...@free-electrons.com>
> ---
> Mike,
>
> this patch could solve the issues we get on severals mvebu platform
> since 3.14-rc1. This is an alternate solution of the patch set sent by
> Sebastian. However as it modifies the clock framework itself, it is
> more sensible.
>
> I find this solution more elegant than changing the order of the
> initialization of the clock at the platform level. However as it
> should be tested on more platforms that only the mvebu ones, it would
> take some time, and I don't want to still have "broken" platform
> during more release candidate. So at the end this patch should be part
> of the 3.15 kernel.
If we can get a response from Mike, I'd prefer to go with this approach
and let it bake in -next for a while. Hopefully, we could get it in
before -rc4...
thx,
Jason.
> drivers/clk/clk.c | 94
> +++++++++++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 91 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 5517944495d8..beb0f8b0c2a0 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -2526,24 +2526,112 @@ 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)
> +{
> + struct of_phandle_args clkspec;
> + struct of_clk_provider *provider;
> +
> + /*
> + * If there is no clock parent, no need to wait for them, then
> + * we can consider their absence as being ready
> + */
> + if (of_parse_phandle_with_args(np, "clocks", "#clock-cells", 0,
> + &clkspec))
> + return 1;
> +
> + /* Check if we have such a provider in our array */
> + list_for_each_entry(provider, &of_clk_providers, link) {
> + if (provider->node == clkspec.np)
> + return 1;
> + }
> +
> + return 0;
> +}
> +
> /**
> * 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;
>
> if (!matches)
> matches = &__clk_of_table;
>
> for_each_matching_node_and_match(np, matches, &match) {
> of_clk_init_cb_t clk_init_cb = match->data;
> - clk_init_cb(np);
> +
> +
> + if (parent_ready(np)) {
> + /*
> + * The parent clock is ready or there is no
> + * clock parent at all, in this case the
> + * provider can be initialize immediately.
> + */
> + clk_init_cb(np);
> + } else {
> + /*
> + * The parent clock is not ready, this
> + * provider is moved to a list to be
> + * initialized later
> + */
> + 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 (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;
> + }
> + }
> +
> + if (!is_init_done) {
> + /*
> + * 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
> + */
> + list_for_each_entry_safe(clk_provider, next,
> + &clk_provider_list, node) {
> + clk_provider->clk_init_cb(clk_provider->np);
> + list_del(&clk_provider->node);
> + kfree(clk_provider);
> + }
> + }
> }
> }
> #endif
> --
> 1.8.1.2
>
>
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> linux-arm-ker...@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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