# \[PATCH V2\] clk: mxs: Fix invalid 32-bit access to frac registers

- From: Marek Vasut \<marex@denx.de\>
- Date: 2015-01-22 00:50:16 
- List: linux-arm-kernel
- Page: https://ratatoskr.run/linux-arm-kernel/2015/01/4414868
- Thread: https://ratatoskr.run/linux-arm-kernel/2014/12/4400518/t.md

```text
On Wednesday, January 21, 2015 at 05:16:03 PM, Zhi Li wrote:
> On Sun, Dec 28, 2014 at 4:26 AM, Stefan Wahren [ref] 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.

Best regards,
Marek Vasut
```