On Wed, Feb 11, 2015 at 09:18:35AM +0900, Simon Horman wrote:

Hi Geert,

On Thu, Feb 05, 2015 at 11:11:23AM +0100, Geert Uytterhoeven wrote:

quoted

        Hi all,

The Renesas Bus State Controller (BSC) provides an external bus for
connecting multiple external devices to an SoC, driving several chip
select lines, for e.g. NOR FLASH, Ethernet and USB.
On the kzm9g and ape6evm development boards, an smsc9220 Ethernet
controller is connnected to the BSC of an SH-Mobile AG5 (sh73a0) resp.
R-Mobile APE6 (r8a73a4) SoC.

The BSC is a fairly simple memory-mapped bus, hence a "simple-bus"
compatibility seems suitable.  However, the BSC is special in two
ways:
  1. It is part of a PM domain (A4S on sh73a0),
  2. It has a gateable functional clock (ZB).
Before a device connected to the BSC can be accessed, the PM domain
containing the BSC must be powered on, and the functional clock
driving the BSC must be enabled.

Both special properties can be described in DT in a standardized way
("power-domains = <&pd_a4s>" and "clocks = <&zb_clk>", cfr. the
example in the DT binding documentation).  Externally connected
devices are described as children of the BSC node.

Unfortunately this doesn't mean everything will work out-of-the-box.
There are two problems:
  1. Without a device driver bound to the bus device, this device is
     not attached to the PM domain. And although a child device is
     present and active, the PM domain may be powered down, as it's
     considered unused by the PM domain core.
  2. Without a device driver calling pm_runtime_enable(), its
     functional clock is not enabled. Once runtime PM is enabled, the
     R-Mobile PM domain platform driver manages the functional clock
     using runtime PM.

As none of the above is really bus hardware-specific (PM domains and
functional clocks in clock domains are handled from genpd and platform
code), this series adds a Simple Power-Managed Bus driver for
transparent busses, which matches against "simple-pm-bus", enables
runtime PM for the bus device, and calls of_platform_populate() to
probe for child devices.
Due to the child-parent relationship of devices connected to the bus,
as long as the device drivers for the child devices are runtime PM
enabled, the bus's PM domain will be powered, and the bus's clock will
be enabled automatically when needed, for both runtime PM and s2ram.

This was tested on sh73a0/kzm9g-multiplatform (by me), and (v3) on
r8a73a4/ape6evm-multiplatform (by Ulrich Hecht). Without this,
Ethernet doesn't work, as the ZB clock is disabled by
clk_disable_unused().

Felipe: It looks like drivers/usb/musb/musb_am335x.c can be removed, if
"ti,am33xx-usb" claims compatibility with "simple-pm-bus"?

As drivers/bus doesn't have a maintainer, and this driver is needed to
move two shmobile platforms away from legacy to multiplatform, I think
this can go in through Simon's shmobile tree.

thanks for persisting with this. From my point of view it appears
to be reviewed and ready.

Does anyone object to me queueing this up for v3.21 in the renesas tree?

Acked-by: Simon Horman <redacted>

As no one has objected and it seems has been thoroughly reviewed
I have queued this up in the renesas tree.

It is part of the renesas-devel-20150215-v3.19 tag.

[snip]