From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: "Gabriel L. Somlo" <gsomlo@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"robh+dt@kernel.org" <robh+dt@kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"ulf.hansson@linaro.org" <ulf.hansson@linaro.org>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
"kgugala@antmicro.com" <kgugala@antmicro.com>,
"mholenko@antmicro.com" <mholenko@antmicro.com>,
"krakoczy@antmicro.com" <krakoczy@antmicro.com>,
"mdudek@internships.antmicro.com"
<mdudek@internships.antmicro.com>,
"paulus@ozlabs.org" <paulus@ozlabs.org>,
"joel@jms.id.au" <joel@jms.id.au>,
"shorne@gmail.com" <shorne@gmail.com>,
"geert@linux-m68k.org" <geert@linux-m68k.org>,
"david.abdurachmanov@sifive.com" <david.abdurachmanov@sifive.com>,
"florent@enjoy-digital.fr" <florent@enjoy-digital.fr>,
"rdunlap@infradead.org" <rdunlap@infradead.org>
Subject: Re: [PATCH v8 3/3] mmc: Add driver for LiteX's LiteSDCard interface
Date: Sat, 8 Jan 2022 19:47:32 +0200 [thread overview]
Message-ID: <CAHp75VcSenjpZdA_wujKju5rHr8bAw2VjfL8RMKb7RW6Zmz4QA@mail.gmail.com> (raw)
In-Reply-To: <YdmPho2GpVcvWUgU@errol.ini.cmu.edu>
On Sat, Jan 8, 2022 at 3:20 PM Gabriel L. Somlo <gsomlo@gmail.com> wrote:
> On Sat, Jan 08, 2022 at 01:26:08PM +0200, Andy Shevchenko wrote:
> > On Sat, Jan 8, 2022 at 3:57 AM Gabriel L. Somlo <gsomlo@gmail.com> wrote:
> > > On Sat, Jan 08, 2022 at 01:54:07AM +0200, Andy Shevchenko wrote:
> > > > On Saturday, January 8, 2022, Gabriel Somlo <gsomlo@gmail.com> wrote:
...
> > > > + u32 div;
> > > > +
> > > > + div = freq ? host->ref_clk / freq : 256U;
> > > >
> > > > + div = roundup_pow_of_two(div);
> > > > + div = clamp(div, 2U, 256U);
> > > >
> > > > Logically seems to me that you may join these two together, because clamped
> > > > range is power-of-2 one.
> > >
> > > `div` needs to be a power-of-2 when written to the LITEX_PHY_CLOCKERDIV
> > > register (below). And clamp() will just enforce a min/max range, so if
> > > (div = ref_clk / freq) ends up e.g., 5, I need both roundup_pow_of_two()
> > > to bump it to 8, and clamp() to enforce that it's between 2 and 256.
> > >
> > > Unless you mean I should simply write it like:
> > >
> > > div = clamp(roundup_pow_of_two(div), 2U, 256U);
> > >
> > > ... as a single line?
> >
> > Yes, that's what I meant.
>
> Turns out, clamp really hates being passed roundup_pow_of_two()
> directly (see below). I think it's probably better if we leave
> them as-is, to avoid going the explicit cast route which Geert
> recommended against.
I see, then ignore my comment on this matter in v9.
Perhaps add a comment in the code explaining that roundup_pow_of_two()
may not be unified with clamp()?
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2022-01-08 17:48 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-07 23:34 [PATCH v8 0/3] mmc: Add LiteSDCard mmc driver Gabriel Somlo
2022-01-07 23:34 ` [PATCH v8 1/3] MAINTAINERS: co-maintain LiteX platform Gabriel Somlo
2022-01-07 23:34 ` [PATCH v8 2/3] dt-bindings: mmc: Add bindings for LiteSDCard Gabriel Somlo
2022-01-07 23:34 ` [PATCH v8 3/3] mmc: Add driver for LiteX's LiteSDCard interface Gabriel Somlo
[not found] ` <CAHp75VcHnHpX1=ojmFnujqkf55aS1ePiVW4kKydTJQe=dXbwbQ@mail.gmail.com>
2022-01-08 1:57 ` Gabriel L. Somlo
2022-01-08 2:31 ` Gabriel L. Somlo
2022-01-08 11:29 ` Andy Shevchenko
2022-01-08 11:26 ` Andy Shevchenko
2022-01-08 13:20 ` Gabriel L. Somlo
2022-01-08 17:47 ` Andy Shevchenko [this message]
2022-01-08 23:51 ` Gabriel L. Somlo
2022-01-09 11:36 ` Andy Shevchenko
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