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Subject: Re: [PATCH v4 07/47] soc: fsl: qe: qe.c: guard use of
 pvr_version_is() with CONFIG_PPC32
To: Timur Tabi <timur@kernel.org>
References: <20191108130123.6839-1-linux@rasmusvillemoes.dk>
 <20191108130123.6839-8-linux@rasmusvillemoes.dk>
 <CAOZdJXXHK9U_Y7_VgVmuOFKDAh4OqBJ7hZx58hisZZ6Cz6xE2w@mail.gmail.com>
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Message-ID: <027c2b7a-a235-cecf-9f08-f71736f2ea55@rasmusvillemoes.dk>
Date: Fri, 15 Nov 2019 09:11:41 +0100
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Cc: lkml <linux-kernel@vger.kernel.org>, Li Yang <leoyang.li@nxp.com>,
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On 15/11/2019 05.50, Timur Tabi wrote:
> On Fri, Nov 8, 2019 at 7:04 AM Rasmus Villemoes
> <linux@rasmusvillemoes.dk> wrote:
>>
>> +static bool qe_general4_errata(void)
>> +{
>> +#ifdef CONFIG_PPC32
>> +       return pvr_version_is(PVR_VER_836x) || pvr_version_is(PVR_VER_832x);
>> +#endif
>> +       return false;
>> +}
>> +
>>  /* Program the BRG to the given sampling rate and multiplier
>>   *
>>   * @brg: the BRG, QE_BRG1 - QE_BRG16
>> @@ -223,7 +231,7 @@ int qe_setbrg(enum qe_clock brg, unsigned int rate, unsigned int multiplier)
>>         /* Errata QE_General4, which affects some MPC832x and MPC836x SOCs, says
>>            that the BRG divisor must be even if you're not using divide-by-16
>>            mode. */
> 
> Can you also move this comment (and fix the comment formatting so that
> it's a proper function comment) to qe_general4_errata()?
> 

I actually thought of doing that, but decided against it because the
comment not only mentions the SOCs affected, but also explains the
following math/logic. I mean, without that comment nearby, the code is

  if (qe_general4_errata())
     if (some weird condition)
        divisor++;

In contrast, I think the qe_general4_errata() is pretty self-explanatory
- is this a SOC affected by that errata (whatever that errata may be
about and what the software workaround is).

Rasmus