linux-kernel - Re: [PATCH V2] clk: mxs: Fix invalid 32-bit access to frac registers

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Message-ID: <20150128015131.22722.22882@quantum>
Date:	Tue, 27 Jan 2015 17:51:31 -0800
From:	Mike Turquette <mturquette@...aro.org>
To:	Marek Vasut <marex@...x.de>, "Zhi Li" <lznuaa@...il.com>
Cc:	"Stefan Wahren" <stefan.wahren@...e.com>,
	"kernel list" <linux-kernel@...r.kernel.org>,
	"Sascha Hauer" <kernel@...gutronix.de>, harald@...ib.org,
	"Shawn Guo" <shawn.guo@...aro.org>,
	"Fabio Estevam" <festevam@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V2] clk: mxs: Fix invalid 32-bit access to frac registers

Quoting Marek Vasut (2015-01-21 15:39:01)
> On Wednesday, January 21, 2015 at 05:16:03 PM, Zhi Li wrote:
> > On Sun, Dec 28, 2014 at 4:26 AM, Stefan Wahren <stefan.wahren@...e.com> wrote:
> > > According to i.MX23 and i.MX28 reference manual the fractional
> > > clock control registers must be addressed by byte instructions.
> > 
> > I don't think mx23 and mx28 have such limitation. I will double check
> > with IC team about this.
> > RTL is generated from a xml file. All registers implement is unified.
> > I don't think only clock control register have such limitation and
> > other registers not.
> 
> Hi,
> 
> Section 10.8.24 in the MX28 datasheet (Fractional Clock Control Register 0) 
> states otherwise, but maybe the documentation is simply not matching the
> silicon.
> 
> Here's a quote:
> "
> This register controls the 9-phase fractional clock dividers. The fractional 
> clock frequencies are a product of the values in these registers. NOTE: This 
> register can only be addressed by byte instructions. Addressing word or half-
> word are not allowed.
> "
> 
> I also recall seeing weird behavior when these registers were accessed by word
> access in U-Boot, so I believe the datasheet is correct.

Hi Frank,

Are you satisfied with this patch?

Regards,
Mike

> 
> Best regards,
> Marek Vasut
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