linux-kernel - Re: [Letux-kernel] [RFC PATCH 0/3] Enable 1GHz support on omap36xx

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Date:   Tue, 10 Sep 2019 21:26:03 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Adam Ford <aford173@...il.com>
Cc:     Tony Lindgren <tony@...mide.com>,
        André Roth <neolynx@...il.com>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andreas Kemnade <andreas@...nade.info>,
        Nishanth Menon <nm@...com>
Subject: Re: [Letux-kernel] [RFC PATCH 0/3] Enable 1GHz support on omap36xx

Hi Adam,

> Am 10.09.2019 um 20:51 schrieb H. Nikolaus Schaller <hns@...delico.com>:
> 
> Hi,
> 
>> Am 10.09.2019 um 20:30 schrieb Adam Ford <aford173@...il.com>:
>> 
>> On Tue, Sep 10, 2019 at 11:59 AM H. Nikolaus Schaller <hns@...delico.com> wrote:
>>> 

>> 
>> I assumed this to be -EINVAL, but I'd be happy to be wrong.
> 
> It seems that cat microvolts stringifies the int returned from reading
> the regulator voltage.
> 
> Since it is initialized to -EINVAL it returns "-22" as string instead of
> converting into an errno return when reading /sys... So one step is
> missing a proper error check.

Ok, found it in regulator_uV_show().

ret = sprintf(buf, "%d\n", regulator_get_voltage_rdev(rdev));

simply prints the result into a string.

But regulator_get_voltage_rdev() (or _regulator_get_voltage() before v5.3-rc1)
may return errors like -EPROBE_DEFER or -EINVAL or whatever
rdev->desc->ops->get_voltage_sel(rdev) returns.

So this is clearly a bug in regulator_uV_show().

> But that is just a symptom that there is no call to set a good voltage.

That is the next issue to find...

BR,
Nikolaus