Re: [PATCH v5 0/5] drivers: bus: Add Simple Power-Managed Bus

[Simon Horman]

Hi Geert,

On Thu, Feb 05, 2015 at 11:11:23AM +0100, Geert Uytterhoeven wrote:
>         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 <horms+renesas@xxxxxxxxxxxx>

> Changes compared to v4:
>   - Add Reviewed-by,
>   - "simple-pm-bus" is not an extension of "simple-bus",
>   - "compatible" must not contain "simple-bus",
>   - Add reference to clock/PM domain provider binding docs.
> 
> Changes compared to v3:
>   - Replace "simple-bus" by "simple-pm-bus" in the bindings,
>   - Move the "renesas,bsc" bindings to a separate document,
>   - Bind against the generic "simple-pm-bus" instead of "renesas,bsc",
>   - Explicitly call of_platform_populate() after pm_runtime_enable() to
>     enforce ordering, instead of depending on claimed compatibility with
>     "simple-bus".
> 
> Changes compared to v2:
>   - Document required properties inherited from "simple-bus",
>   - Document required "reg" property for "renesas,bsc",
>   - Move "ranges" before "reg" in the example,
>   - Add Tested-by,
>   - Split-off sh73a0/kzm9g and r8a73a4/ape6evm DTS updates.
> 
> Changes compared to v1 (more detailed change logs in the individual
> patches):
>   - Added sorting of drivers/bus Kconfig and Makefile entries,
>   - Added DT binding documentation,
>   - Rename from "Renesas Bus State Controller Driver" (renesas-bsc) to
>     "Simple Power-Managed Bus Driver" (simple-pm-bus),
>   - Postponed adding power-domains properties to the dtsi,
>   - Added updates for r8a73a4/ape6evm.
> 
> Thanks!
> 
> Geert Uytterhoeven (5):
>   drivers: bus: Sort Kconfig entries alphabetically
>   drivers: bus: Sort Makefile entries alphabetically
>   drivers: bus: Add Simple Power-Managed Bus DT Bindings
>   drivers: bus: Add Renesas Bus State Controller (BSC) DT Bindings
>   drivers: bus: Add Simple Power-Managed Bus Driver
> 
>  .../devicetree/bindings/bus/renesas,bsc.txt        | 46 +++++++++++++++++
>  .../devicetree/bindings/bus/simple-pm-bus.txt      | 44 ++++++++++++++++
>  drivers/bus/Kconfig                                | 53 ++++++++++++--------
>  drivers/bus/Makefile                               | 15 +++---
>  drivers/bus/simple-pm-bus.c                        | 58 ++++++++++++++++++++++
>  5 files changed, 189 insertions(+), 27 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/bus/renesas,bsc.txt
>  create mode 100644 Documentation/devicetree/bindings/bus/simple-pm-bus.txt
>  create mode 100644 drivers/bus/simple-pm-bus.c
> 
> -- 
> 1.9.1
> 
> Gr{oetje,eeting}s,
> 
> 						Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> 							    -- Linus Torvalds
> 
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