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

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Message-ID: <CAOMZO5DOgdUYsRUU3TXgJY+JhjF8xC_XY8EJFcrM7NHiPmSMOQ@mail.gmail.com>
Date:	Tue, 10 Feb 2015 10:52:52 -0200
From:	Fabio Estevam <festevam@...il.com>
To:	Stefan Wahren <stefan.wahren@...e.com>
Cc:	Mike Turquette <mturquette@...aro.org>,
	Marek Vasut <marex@...x.de>, Zhi Li <lznuaa@...il.com>,
	Sascha Hauer <kernel@...gutronix.de>, harald@...ib.org,
	Shawn Guo <shawn.guo@...aro.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V2 RESEND] clk: mxs: Fix invalid 32-bit access to frac registers

Hi Stefan,

On Fri, Jan 30, 2015 at 5:20 PM, Stefan Wahren <stefan.wahren@...e.com> wrote:
> According to i.MX23 and i.MX28 reference manual [1],[2] the fractional
> clock control register is 32-bit wide, but is separated in 4 parts.
> So write instructions must not apply to more than 1 part at once.
>
> The clk init for the i.MX28 violates this restriction and all the other
> accesses on that register suggest that there isn't such a restriction.
>
> This patch restricts the access to this register to byte instructions and
> extends the comment in the init functions.
>
> Btw the imx23 init now uses a R-M-W sequence just like imx28 init
> to avoid any clock glitches.
>
> The changes has been tested with a i.MX23 and a i.MX28 board.
>
> [1] - http://cache.freescale.com/files/dsp/doc/ref_manual/IMX23RM.pdf
> [2] - http://cache.freescale.com/files/dsp/doc/ref_manual/MCIMX28RM.pdf
>
> Signed-off-by: Stefan Wahren <stefan.wahren@...e.com>
> Reviewed-by: Marek Vasut <marex@...x.de>
> ---
>
> Changes in V2:
> - use relaxed access operations in clk-ref

With this patch applied mx28evk cannot probe SPI NOR flash:

m25p80 spi1.0: unrecognized JEDEC id bytes: bf, 24, 40

Reverting it from linux-next, then the SPI NOR probe correctly.

m25p80 spi1.0: sst25vf016b (2048 Kbytes)

Any ideas?

Thanks for the suggestion, Marek!

Regards,

Fabio Estevam
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