linux-kernel - Re: [PATCH 1/8] clk: add helper for unique DT clock names

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Message-ID: <53727E6E.6050503@gmail.com>
Date:	Tue, 13 May 2014 22:19:58 +0200
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Mike Turquette <mturquette@...aro.org>
CC:	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Antoine Tenart <antoine.tenart@...e-electrons.com>,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] clk: add helper for unique DT clock names

On 05/13/2014 09:49 PM, Mike Turquette wrote:
> Quoting Sebastian Hesselbarth (2014-05-11 13:24:34)
>> Currently, most DT clock drivers pick a unique node name to allow unique
>> clock names. As ePAPR recommends node names to be generic, we therefore
>> provide a helper to generate a unique clock name from the DT node name
>> plus reg property or a magic number instead. This is basically the same
>> we already do for proper devices and may vanish as soon as there is some
>> (early) device support for clocks available.
>>
>> Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
[...]
>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>> index dff0373f53c1..b449a635dbfa 100644
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -17,6 +17,7 @@
>>  #include <linux/list.h>
>>  #include <linux/slab.h>
>>  #include <linux/of.h>
>> +#include <linux/of_address.h>
>>  #include <linux/device.h>
>>  #include <linux/init.h>
>>  #include <linux/sched.h>
>> @@ -2543,6 +2544,34 @@ const char *of_clk_get_parent_name(struct device_node *np, int index)
>>  }
>>  EXPORT_SYMBOL_GPL(of_clk_get_parent_name);
>>  
>> +/**
>> + * of_clk_create_name() - Allocate and create a unique clock name
>> + * @np: Device node pointer of the clock node
>> + *
>> + * This will allocate and create a unique clock name based on the
>> + * reg property value. As a last resort, it will use the node name
>> + * followed by a unique number. The caller has to deallocate the
>> + * buffer.
>> + */
>> +char *of_clk_create_name(struct device_node *np)
>> +{
>> +       static atomic_t clk_no_reg_magic;
>> +       const __be32 *reg;
>> +       u64 addr;
>> +       int magic;
>> +
>> +       reg = of_get_property(np, "reg", NULL);
>> +       if (reg) {
>> +               addr = of_translate_address(np, reg);
>> +               return kasprintf(GFP_KERNEL, "%llx.%s",
>> +                                (unsigned long long)addr, np->name);
>> +       }
>> +
>> +       magic = atomic_add_return(1, &clk_no_reg_magic);
>> +       return kasprintf(GFP_KERNEL, "%s.%d", np->name, magic);
> 
> For the case where we the reg property is present we use reg.name, but
> for the case were the reg property is missing we use name.magic. Is it
> intentional to switch the string and integer pairs?
> 
> Doing so avoids the case where magic might collide with a simple bus
> clock (e.g. 'clk@1'), but I wanted to double check that it was
> intentional.

Mike,

yes it is intentional and copies what is done for platform_device names.

Unfortunately, as much as I prefer this patch someday, it doesn't work
with the rest of the helpers as expected. While this can generate unique
and generic clock names, especially of_clk_get_parent_name() picks
either an clock-output-names named clock _or_ the node name ignoring the
above auto-generated name of course.

If you agree with the general approach here, we should still postpone
this for the next cycle when I have more time to look at the details.
I prefer to rename the nodes and use clock-output-names where required
for the Berlin clock nodes now.

Sebastian

>> +}
>> +EXPORT_SYMBOL_GPL(of_clk_create_name);
>> +
>>  struct clock_provider {
>>         of_clk_init_cb_t clk_init_cb;
>>         struct device_node *np;
>> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
>> index 511917416fb0..c6f3ca1cd81c 100644
>> --- a/include/linux/clk-provider.h
>> +++ b/include/linux/clk-provider.h
>> @@ -514,6 +514,7 @@ struct clk *of_clk_src_simple_get(struct of_phandle_args *clkspec,
>>  struct clk *of_clk_src_onecell_get(struct of_phandle_args *clkspec, void *data);
>>  int of_clk_get_parent_count(struct device_node *np);
>>  const char *of_clk_get_parent_name(struct device_node *np, int index);
>> +char *of_clk_create_name(struct device_node *np);
>>  
>>  void of_clk_init(const struct of_device_id *matches);
>>  
>> @@ -543,6 +544,10 @@ static inline const char *of_clk_get_parent_name(struct device_node *np,
>>  {
>>         return NULL;
>>  }
>> +static inline char *of_clk_create_name(struct device_node *np)
>> +{
>> +       return NULL;
>> +}
>>  #define of_clk_init(matches) \
>>         { while (0); }
>>  #endif /* CONFIG_OF */
>> -- 
>> 1.9.1
>>

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