Re: [PATCH v4 12/19] cpufreq: cpufreq-cpu0: remove device tree parsing for cpu nodes

[Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>]

On 06/09/13 14:44, Guennadi Liakhovetski wrote:
> Hi
>=20
> On Tue, 20 Aug 2013, Sudeep KarkadaNagesha wrote:
>=20
>> From: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
>>
>> Now that the cpu device registration initialises the of_node(if availabl=
e)
>> appropriately for all the cpus, parsing here is redundant.
>>
>> This patch removes all DT parsing and uses cpu->of_node instead.
>>
>> Acked-by: Shawn Guo <shawn.guo@linaro.org>
>> Acked-by: Rob Herring <rob.herring@calxeda.com>
>> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
>> Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
>> ---
>>  drivers/cpufreq/cpufreq-cpu0.c | 23 ++++-------------------
>>  1 file changed, 4 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq-cpu0.c b/drivers/cpufreq/cpufreq-cp=
u0.=3D
>> c
>> index ad1fde2..5b05c26 100644
>> --- a/drivers/cpufreq/cpufreq-cpu0.c
>> +++ b/drivers/cpufreq/cpufreq-cpu0.c
>> @@ -174,29 +174,17 @@ static struct cpufreq_driver cpu0_cpufreq_driver =
=3D3D =3D
>> {
>> =3D20
>>  static int cpu0_cpufreq_probe(struct platform_device *pdev)
>>  {
>> -=3D09struct device_node *np, *parent;
>> +=3D09struct device_node *np;
>>  =3D09int ret;
>> =3D20
>> -=3D09parent =3D3D of_find_node_by_path("/cpus");
>> -=3D09if (!parent) {
>> -=3D09=3D09pr_err("failed to find OF /cpus\n");
>> -=3D09=3D09return -ENOENT;
>> -=3D09}
>> -
>> -=3D09for_each_child_of_node(parent, np) {
>> -=3D09=3D09if (of_get_property(np, "operating-points", NULL))
>> -=3D09=3D09=3D09break;
>> -=3D09}
>> +=3D09cpu_dev =3D3D &pdev->dev;
>> =3D20
>> +=3D09np =3D3D of_node_get(cpu_dev->of_node);
>=20
> Has this actually been tested? This seems to break cpufreq-cpu0. The=20
> reason is, that this probe function is called not for the DT CPU node, bu=
t=20
> for a special virtual cpufreq-cpu0 platform device, typically created by=
=20
> platforms, using
>=20
> =09platform_device_register_simple("cpufreq-cpu0", -1, NULL, 0);
>=20
> which then of course doesn't have on .of_node associated with it.
>=20

Hi Guennadi,

Based on my understanding of the original code:
        cpu_dev =3D &pdev->dev;
=09...
=09ret =3D of_init_opp_table(cpu_dev);

of_init_opp_table needs cpu_dev to be get_cpu_device(0). My
understanding was that platform using cpufreq-cpu0 sets &pdev->dev to
get_cpu_device(0). But looks like that's not the case.

Hi Shawn,

Can you please clarify ? The fix would be as below but I would like to
know if setting cpu_dev to get_cpu_device(0) instead of &pdev->dev has
any impact on other parts of code using cpu_dev ?

diff --git a/drivers/cpufreq/cpufreq-cpu0.c b/drivers/cpufreq/cpufreq-cpu0.=
c
index cbfffa9..871c336 100644
--- a/drivers/cpufreq/cpufreq-cpu0.c
+++ b/drivers/cpufreq/cpufreq-cpu0.c
@@ -177,7 +177,7 @@ static int cpu0_cpufreq_probe(struct platform_device
*pdev)
        struct device_node *np;
        int ret;

-       cpu_dev =3D &pdev->dev;
+       cpu_dev =3D get_cpu_device(0);

        np =3D of_node_get(cpu_dev->of_node);
        if (!np) {


Regards,
Sudeep