regmap: how to support devices with 'nested' pages

regmap: how to support devices with 'nested' pages

[Peter Ujfalusi]

Hi Mark,

I got a device which registers are arranged in 'books' and pages:

book0
 page0
 page1
 ...
 page127
book1
 page0
 page1
 ...
 page127
...
book255
 page0
 page1
 ...
 page127

The pages can be selected via register0 of each page (in a standard way),
however the book switching can only be done via each book's page0's reg127.

With regmap's ranges I can get the pages covered, but with that I can only
stay within one book.

At power on the chip is at book0, page0.
If I want to access book0, page2:
write 2 to reg0 // to switch to page2
access to the desired register in book0, page2

Now if I want to access let's say book3, page4:
write 0 to reg0 // to switch to page0 of book0
write 3 to reg127 // to switch to book3
write 4 to reg0 // to switch to page4 of book3
access to the desired register

Do you know any other device which have similar addressing? Do you have advice
on how to handle this? Should I open code the book switching in the driver,
which means that I should not use the cache at all in regmap.

Thank you,
Péter

Re: regmap: how to support devices with 'nested' pages

[Mark Brown]

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On Tue, Mar 10, 2015 at 11:33:24AM +0200, Peter Ujfalusi wrote:

> Do you know any other device which have similar addressing? Do you have advice
> on how to handle this? Should I open code the book switching in the driver,
> which means that I should not use the cache at all in regmap.

I've never heard of any other devices doing anything similar, it's
certainly innovative.  I've no great idea how to deal with it other than
try to make the page selection code cope with recursion or nest some
regmaps.

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