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

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Message-ID: <CAHrpEqSFfdWsCif_wZO2ToRpwOuC2yt45+HwOpGgv+B=EwKTCw@mail.gmail.com>
Date:	Tue, 27 Jan 2015 21:36:38 -0600
From:	Zhi Li <lznuaa@...il.com>
To:	Mike Turquette <mturquette@...aro.org>
Cc:	Marek Vasut <marex@...x.de>,
	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

On Tue, Jan 27, 2015 at 7:51 PM, Mike Turquette <mturquette@...aro.org> wrote:
> 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?

I asked IC designer about this.
They will check RTL code.
I will check their status again.
Our released BSP code used 32bit WORD access.

best regards
Frank Li
>
> Regards,
> Mike
>
>>
>> Best regards,
>> Marek Vasut
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