From: Ben Hutchings <ben.hutchings@codethink.co.uk>
To: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Simon <horms@verge.net.au>,
Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>,
Linux-SH <linux-sh@vger.kernel.org>,
Laurent <laurent.pinchart@ideasonboard.com>,
Ian Molton <ian@mnementh.co.uk>,
Geert Uytterhoeven <geert@linux-m68k.org>,
linux-kernel@lists.codethink.co.uk, linux-gpio@vger.kernel.org,
linux-mmc@vger.kernel.org
Subject: Re: [PATCH v3 5/6] ARM: shmobile: lager: Set clock rates for SDHI
Date: Tue, 30 Jun 2015 03:06:39 +0100 [thread overview]
Message-ID: <1435629999.23818.52.camel@codethink.co.uk> (raw)
In-Reply-To: <87zj3ieztx.wl%kuninori.morimoto.gx@renesas.com>
On Tue, 2015-06-30 at 01:45 +0000, Kuninori Morimoto wrote:
> Hi Ben
>
> > > > > SH-MMC is using this style. and I think it is flexible for every speed.
> > > > > Please check sh_mmcif_clock_control(), sh_mmcif_clk_setup()
> > > > > on ${LINUX}/drivers/mmc/host/sh_mmcif.c
> > > >
> > > > That's certainly a nicer way of doing this. The difficulty I see is
> > > > that tmio_mmc doesn't know anything about the input clock, and not all
> > > > of the drivers using it actually use the clock framework.
> > >
> > > More importantly, that algrithm can result in overclocking the card.
> >
> > ...and some of the multiplications overflow!
>
> Can you show us more detail ?
> It seems bug...
The requested clock rate can be up to 52 MHz and the divider can be up
to 1024. With div == 1024 and clk == 52000000, clk * div overflows.
Ben.
next prev parent reply other threads:[~2015-06-30 2:06 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-26 15:21 [PATCH v3 0/6] UHS-I support for sh_mobile_sdhi Ben Hutchings
2015-06-26 15:22 ` [PATCH v3 1/6] mmc: tmio: Add UHS-I mode support Ben Hutchings
2015-06-26 15:23 ` [PATCH v3 2/6] pinctrl: sh-pfc: Implement pinconf power-source param for voltage switching Ben Hutchings
2015-06-29 8:17 ` Geert Uytterhoeven
2015-06-29 8:32 ` Laurent Pinchart
2015-06-29 21:55 ` Ben Hutchings
2015-06-26 15:23 ` [PATCH v3 3/6] pinctrl: sh-pfc: r8a7790: Implement voltage switching for SDHI Ben Hutchings
2015-06-29 8:50 ` Laurent Pinchart
2015-06-29 23:44 ` Ben Hutchings
2015-06-26 15:23 ` [PATCH v3 4/6] mmc: sh_mobile_sdhi: Add UHS-I mode support Ben Hutchings
2015-06-26 15:23 ` [PATCH v3 5/6] ARM: shmobile: lager: Set clock rates for SDHI Ben Hutchings
2015-06-29 6:23 ` Kuninori Morimoto
2015-06-30 0:02 ` Ben Hutchings
2015-06-30 1:29 ` Ben Hutchings
2015-06-30 1:31 ` Ben Hutchings
2015-06-30 1:45 ` Kuninori Morimoto
2015-06-30 2:06 ` Ben Hutchings [this message]
2015-06-30 4:43 ` Kuninori Morimoto
2015-06-26 15:23 ` [PATCH v3 6/6] ARM: shmobile: lager: Enable UHS-I SDR-50 Ben Hutchings
2015-06-26 15:25 ` [PATCH v3 0/6] UHS-I support for sh_mobile_sdhi Ben Hutchings
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