linux-kernel - Re: [PATCH 07/26] clk: vt8500: parse pmc

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Date:	Fri, 20 Sep 2013 16:51:30 +1200
From:	Tony Prisk <linux@...sktech.co.nz>
To:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
CC:	Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>,
	Mike Turquette <mturquette@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/26] clk: vt8500: parse pmc_base from clock driver

On 20/09/13 07:12, Sebastian Hesselbarth wrote:
> On 09/19/2013 09:02 PM, Tony Prisk wrote:
>> On 19/09/13 05:53, Sebastian Hesselbarth wrote:
>>> Currently, clock providers for vt8500 depend on machine_init providing
>>> pmc_base address before calling of_clk_init. With upcoming arch-wide
>>> .time_init calling of_clk_init, we should make clock providers
>>> independent
>>> of mach code. This adds a pmc_base parsing helper to current clock
>>> provider
>>> that gets called if there is no pmc_base set, yet.
>>>
>>> Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
>>> ---
>>> Cc: Olof Johansson <olof@...om.net>
>>> Cc: Arnd Bergmann <arnd@...db.de>
>>> Cc: Tony Prisk <linux@...sktech.co.nz>
>>> Cc: Mike Turquette <mturquette@...aro.org>
>>> Cc: linux-arm-kernel@...ts.infradead.org
>>> Cc: linux-kernel@...r.kernel.org
>>> ---
>>>   drivers/clk/clk-vt8500.c |   21 +++++++++++++++++++++
>>>   1 file changed, 21 insertions(+)
>>>
>>> diff --git a/drivers/clk/clk-vt8500.c b/drivers/clk/clk-vt8500.c
>>> index 82306f5..a5ee01c 100644
>>> --- a/drivers/clk/clk-vt8500.c
>>> +++ b/drivers/clk/clk-vt8500.c
>>> @@ -15,11 +15,14 @@
>>>   #include <linux/io.h>
>>>   #include <linux/of.h>
>>> +#include <linux/of_address.h>
>>>   #include <linux/slab.h>
>>>   #include <linux/bitops.h>
>>>   #include <linux/clkdev.h>
>>>   #include <linux/clk-provider.h>
>>> +#define LEGACY_PMC_BASE        0xD8130000
>>> +
>>>   /* All clocks share the same lock as none can be changed
>>> concurrently */
>>>   static DEFINE_SPINLOCK(_lock);
>>> @@ -626,6 +629,21 @@ const struct clk_ops vtwm_pll_ops = {
>>>       .recalc_rate = vtwm_pll_recalc_rate,
>>>   };
>>> +static __init void vtwm_set_pmc_base(void)
>>> +{
>>> +    struct device_node *np =
>>> +        of_find_compatible_node(NULL, NULL, "via,vt8500-pmc");
>>> +
>>> +    if (np)
>>> +        pmc_base = of_iomap(np, 0);
>>> +    else
>>> +        pmc_base = ioremap(LEGACY_PMC_BASE, 0x1000);
>>> +    of_node_put(np);
>>> +
>>> +    if (!pmc_base)
>>> +        pr_err("%s:of_iomap(pmc) failed\n", __func__);
>>> +}
>>> +
>>>   static __init void vtwm_pll_clk_init(struct device_node *node, int
>>> pll_type)
>>>   {
>>>       u32 reg;
>>> @@ -636,6 +654,9 @@ static __init void vtwm_pll_clk_init(struct
>>> device_node *node, int pll_type)
>>>       struct clk_init_data init;
>>>       int rc;
>>> +    if (!pmc_base)
>>> +        vtwm_set_pmc_base();
>>> +
>>>       rc = of_property_read_u32(node, "reg", &reg);
>>>       if (WARN_ON(rc))
>>>           return;
>> What happens if the first clock registered is a 'device clock' rather
>> than a 'pll'?
>>
>> static __init void vtwm_device_clk_init(struct device_node *node)
>> {
>>      u32 en_reg, div_reg;
>>      struct clk *clk;
>>      struct clk_device *dev_clk;
>>      const char *clk_name = node->name;
>>      const char *parent_name;
>>      struct clk_init_data init;
>>      int rc;
>>      int clk_init_flags = 0;
>>
>>      dev_clk = kzalloc(sizeof(*dev_clk), GFP_KERNEL);
>>      if (WARN_ON(!dev_clk))
>>          return;
>>
>>      dev_clk->lock = &_lock;
>>
>>      rc = of_property_read_u32(node, "enable-reg", &en_reg);
>>      if (!rc) {
>>          dev_clk->en_reg = pmc_base + en_reg;
>> ...
>> }
>> CLK_OF_DECLARE(vt8500_device, "via,vt8500-device-clock",
>> vtwm_device_clk_init);
>>
>> If a device clock is initialized first, pmc_base will be null and
>> dev_clk->en_reg (+ other register offsets) will be incorrect.
>
> Tony,
>
> looks like I just missed to add the same check for !pmc_base to
> vtwm_device_clk_init. If you are ok with the general approach,
> I send v2 for this patch shortly.
>
> Optionally, you can also choose to take care of clk-vt8500 yourself,
> as mach-vt8500 has its own .init_time callback and will be unaffected
> by the arch-wide default callback. If so, I will drop vt8500 to not
> stall this series too much now.
>
> Sebastian
I have no issue with the concept - just pointing out the missing bit. If 
you can fix that small issue for v2 then you can also add my:

Acked-by: Tony Prisk <linux@...sktech.co.nz>

Regards
Tony P
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