Subject: Re: [PATCH v2] [2.6.22] pasemi: cpufreq driver

From: [email-masked] (Olof Johansson)
Date: Thu, 26 Apr 2007 15:26:32 -0500

On Thu, Apr 26, 2007 at 07:11:21PM +0200, Arnd Bergmann wrote:
> On Thursday 26 April 2007, Olof Johansson wrote:
> > SDC is the system and debug controller, it contains a number of smaller
> > devices such as the PIC, the PMU (Gizmo), RNG, and various debug
> > features. Some already have drivers submitted, others will later on.
> 
> Oh well, these chips all seem to be the same. On cell, we have solved
> the problem by introducing the 'cbe_regs' helper library that gives
> access to all those miscellaneous registers to the individual device
> drivers, so that not all of them need to scan the device tree for
> the same registers and map them individually.

Not a bad idea, I'll consider it for the future. Most of our devices are
on a pseudo-PCI bus, so it's only a handful that need special register
access. The stuff in the SDC is the biggest exception.

> The problem with an of_platform_driver for this would be that you
> can only have _one_ driver attached to the registers.
>
> > Unfortunately the setting of the current active state is done to an SDC
> > register, while information of the states is in the PMU, so access to
> > both is needed in the driver.
> 
> One thing that you could do is to list only this one register of the
> SDC in the reg property, not all of the SDC. 

That doesn't make much sense in this case. The register isn't in the
Gizmo.

Having a driver/library for the SDC that the gizmo driver can use is a
good idea, similar to what you've done on cell. I'll try to have that
ready for 2.6.23, but that shouldn't stop this base driver from going
in now.

-Olof