linux-kernel - Re: [PATCH 4/8] clk: davinci: add a reset lookup table for psc0

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Date:   Wed, 21 Mar 2018 17:08:04 +0100
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     David Lechner <david@...hnology.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>, Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        linux-devicetree <devicetree@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-clk@...r.kernel.org,
        linux-remoteproc@...r.kernel.org
Subject: Re: [PATCH 4/8] clk: davinci: add a reset lookup table for psc0

2018-03-21 17:01 GMT+01:00 David Lechner <david@...hnology.com>:
> On 03/21/2018 07:08 AM, Bartosz Golaszewski wrote:
>>
>> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>
>> In order to be able to use the reset framework in legacy boot mode as
>> well, add the reset lookup table to the psc driver for da850 variant.
>>
>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
>> ---
>>   drivers/clk/davinci/psc-da850.c | 8 ++++++++
>>   drivers/clk/davinci/psc.c       | 1 +
>>   2 files changed, 9 insertions(+)
>>
>> diff --git a/drivers/clk/davinci/psc-da850.c
>> b/drivers/clk/davinci/psc-da850.c
>> index ccc7eb17bf3a..395db4b2c0ee 100644
>> --- a/drivers/clk/davinci/psc-da850.c
>> +++ b/drivers/clk/davinci/psc-da850.c
>> @@ -6,6 +6,7 @@
>>    */
>>     #include <linux/clk-provider.h>
>> +#include <linux/reset-controller.h>
>>   #include <linux/clk.h>
>>   #include <linux/clkdev.h>
>>   #include <linux/init.h>
>> @@ -66,8 +67,15 @@ LPSC_CLKDEV3(ecap_clkdev,    "fck",  "ecap.0",
>>                                 "fck",  "ecap.1",
>>                                 "fck",  "ecap.2");
>>   +static struct reset_control_lookup da850_psc0_reset_lookup_table[] = {
>> +       RESET_LOOKUP("davinci-rproc.0", NULL, 15),
>> +};
>> +
>>   static int da850_psc0_init(struct device *dev, void __iomem *base)
>>   {
>> +       reset_controller_add_lookup("da850-psc0",
>> +                                   da850_psc0_reset_lookup_table,
>> +
>> ARRAY_SIZE(da850_psc0_reset_lookup_table));
>
>
> Could there be a race condition here since you are adding the lookup
> *before*
> you are adding the actual provider? It seems like
> reset_controller_add_lookup()
> should be after davinci_psc_register_clocks().
>

I don't think so, because reset_controller_add_lookup() only adds the
lookup structure to the list in reset/core.c. The actual reset
controller struct is only located and used when reset_control_get_*()
is called, so after probing the user. And it's all protected with
mutexes.

This made me think though - maybe if we can't locate the controller,
we should return -EPROBE_DEFER from probe in davinci-rproc?

Bart