From: Geert Uytterhoeven

On Fri, Feb 28, 2014 at 12:37 PM, Marc Kleine-Budde [off-list ref] wrote:

quoted

quoted

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A 32 bit read/modify/write is a standard operation, nothing special, no
need to worry about byte swapping or anything like this.

   Oh, really? 8-)
   Don't you know that read[bwlq]() assume little-endian memory layout
and to read from big-endian 32-bit register one normally needs readl_be()?

I assume you are on little endian ARM only (for now).

If you use a standard 32 bit read, then modify the correct bits in that
32 bit word and write it back, with the corresponding 32 bit write
everything should be fine. For this usecase you just have yo figure out
which 24 of the 32 bit are the one you have to change and which are the
8 that must not be modified.

Looking at the register layout:

quoted

+     u8 bcr[3];      /* Bit Configuration Register */
+     u8 clkr;        /* Clock Select Register */

I think clkr would be the lowest 8 bit and bcr[] are the upper 24.

That would be the outcome on big endian ;-)

Looks to me as though it should be defined as a 32bit field and then
the appropriate bit definitions and masks applied.

	David