Re: [PATCHv1] rtc: bcm-iproc: Add support for Broadcom iproc rtc

From: Arun Ramamurthy
Date: Wed Mar 11 2015 - 16:00:23 EST

On 15-03-04 02:58 PM, Arnd Bergmann wrote:
On Wednesday 04 March 2015 14:53:40 Arun Ramamurthy wrote:
On 15-03-04 02:50 PM, Arnd Bergmann wrote:
On Wednesday 04 March 2015 14:40:13 Arun Ramamurthy wrote:
On 15-03-04 02:21 PM, Arnd Bergmann wrote:
On Thursday 12 February 2015 14:17:41 Arun Ramamurthy wrote:
Hi Arnd

My apologies for the late reply, I was moved to other work items. I
wanted to get more clarification on the syscon issue so that I can
submit the next patch set. If I understand correctly, you would like
me to move the CRMU logic to a new driver under mfd/ and use the syscon
api calls in my rtc driver? Thanks

It depends a lot on what's in there, I can best advise you if you
have some form of register list.

A common approach would be to not have a driver for the crmu at all,
but just mark it as syscon, and have the other drivers either reference
the syscon node through a phandle, or create them as childrem of
the syscon node. The latter case makes most sense if all uses of
the crmu have no other MMIO registers.

Thank you Arnd, I am going to follow the approach of adding a child node
to the syscon node. Several other driver use other registers in the CRMU
so I think the child node approach makes the most sense.

Just to be sure we have the same understanding: of those other drivers,
do you think that they would use only CRMU registers, or could there
be drivers that have both CRMU as well as other MMIO registers?

The other drivers have both CRMU and other MMIO registers. So I thought
they could also switch to using the syscon child nodes.

No, in this case, better not use child nodes at all. When other platforms
use child nodes of a syscon, the common case is that they use the 'reg'
property to refer to syscon registers, which are in a different address
space from other MMIO, and you can't easily mix the two.

Arnd, this is the device tree entry that I would end up with and I plan to use syscon_regmap_lookup_by_phandle in the rtc driver. Does this look acceptable?

rtc: iproc_rtc@0x03026000 {
compatible = "brcm,iproc-rtc";
reg = <0x03026000 0xC>,
iso_cell_syscon = <&crmu_iso_cell_control>;
bbl_auth_syscon = <&crmu_bbl_auth>
status = "okay";

crmu_iso_cell_control:crmu@0x0301C02C {
compatible = "syscon";
reg = <0x0301C038 0x8>

crmu_bbl_auth:crmu@0x03024C74 {
compatible = "syscon";
reg = <0x03024C74 0x8>;


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