Re: CPU revision IDs

On Fri, Jun 13, 2014 at 10:37:37AM -0400, jonsmirl-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:

quoted

quoted

Then I end up with code in the machine file like this...

find SOC revision
if revision == A
    fix up codec and i2s driver compatible
if revision == B
    fix up HDMI compatible
if revision == C
    fix up whatever
I've seen chips with revision levels of J

Why do you want this knowledge in the machine file? Why not just add
the test for SOC revision inside the device driver?

Because it's going to be a mess anyway. No matter if it's in the
driver or the machine code. So at least, that way, we're having it
centralized and isolated from the driver's code.

The mess is always going to be in the driver code. You are just
changing the the string the driver code selects on...

if (of_machine_is_compatible("allwinner,sun7i-codec-rev-a")) {
      fix bug
}

if (of_machine_is_compatible("allwinner,sun7i-a20a")) {
      fix bug
}

What? Hmmm, nope. Look at how we're doing this for the i2c driver
(drivers/i2c/busses/i2c-mv64xxx.c).

The mess is not required in the machine file.  Init time code can
always modify the machine compatible string like this with no side
effects. It would add 'a'-'j' as appropriate for the CPU.

Code changes this:
 compatible = "cubietech,cubietruck", "allwinner,sun7i-a20"
to:
 compatible = "cubietech,cubietruck",  "allwinner,sun7i-a20-a",
"allwinner,sun7i-a20"

Again, this is the machine compatible, and this is orthogonal to the
issue. You should have a different compatible string for the *codec*.

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com