[PATCH v2 0/4] arm: renesas: Add reset control properties
horms at verge.net.au
Mon Mar 20 01:28:52 PDT 2017
On Thu, Mar 16, 2017 at 03:07:22PM +0100, Geert Uytterhoeven wrote:
> Hi Simon, Magnus, Laurent, Morimoto-san,
> This patch series describes the reset control topology for on-SoC devices
> connected to the Renesas Clock Pulse Generator / Module Standby and
> Software Reset module on the R-Car H3 and M3-W, RZ/G1M, and RZ/G1E SoCs.
> Resets usually match the corresponding module clocks. Exceptions are:
> - The Display Unit has only 2 resets, one per channel pair, cfr.
> "[PATCH v2] dt-bindings: drm: rcar-du: Document optional reset
> properties" (http://www.spinics.net/lists/dri-devel/msg134637.html),
> - The audio module has resets for the Serial Sound Interfaces only.
> Adding resets and reset-names properties depends on a DT binding
> update for renesas,rsnd (note: the DT binding documentation in
> Documentation/devicetree/bindings/sound/renesas,rsnd.txt doesn't
> even document clocks and clock-names?).
> Upon request from Laurent for the DU, and upon a DT bindings update
> for rcar_sound, the addition of resets (and reset-names) properties for
> these complex modules is postponed.
> Note that this patch series contains hardware description only.
> Actual reset policy is to be defined and implemented separately.
> Also, this is an optional feature, to be enabled explicitly using
> CONFIG_RESET_CONTROLLER=y. When enabled, an on-SoC device can be reset
> easily using device_reset(), or by using the reset_control_*() API when
> more fine-grained control is desired.
> Possible use cases are (not exhaustive):
> - Reset a device before use, to make sure it's in a predefined state, and
> doesn't depend on earlier configuration by e.g. the boot loader,
> - Reset a device after detecting an anomaly,
> - Reset a device to verify suspend/resume is handled correctly by the
> driver in case the device would be part of a power domain on a
> different/future SoC.
> Dependencies and impact:
> - The corresponding driver changes to the CGP/MSSR driver are already
> present in v4.11-rc1.
> - These patches have no impact as long as CONFIG_RESET_CONTROLLER=n.
> However, if CONFIG_RESET_CONTROLLER=y and resets properties are
> prsesent in DTS, the EHCI and OHCI drivers already deassert reset as
> part of their initialization sequences, and put the devices back
> into reset state in case initialization failed, or on unbind.
> I'm not aware of other relevant drivers already using reset control.
It appears that for arm64 defconfig CONFIG_RESET_CONTROLLER=y is true so
by default there will be a behavioural change on arm64. I'd like to
understand if it is a desirable (or at least not undesirable) change.
> For testing, these patches are also available in the
> topic/renesas-cpg-mssr-reset-dts-v2 branch of my renesas-drivers git
> repository at
> This has been tested on the R-Car Gen3 Salvator-X (H3 and M3-W) and the
> R-Car M2-W (using out-of-tree driver modifications) Koelsch development
> boards, by inspecting device register contents before and after reset,
> and by comparing them with their documented reset values.
> Changes compared to v1:
> - Break out from "[PATCH 0/8] Renesas CPG/MSSR Reset Control Support"
> - Postpone adding resets and reset-names properties for complex
> devices (du, rcar_sound),
> - Rebase on top of renesas-devel-20170313-v4.11-rc2,
> - Add reset properties to recently added device nodes.
> Thanks for applying!
> Geert Uytterhoeven (4):
> arm64: dts: r8a7795: Add reset control properties
> arm64: dts: r8a7796: Add reset control properties
> ARM: dts: r8a7743: Add reset control properties
> ARM: dts: r8a7745: Add reset control properties
> arch/arm/boot/dts/r8a7743.dtsi | 24 +++++++++
> arch/arm/boot/dts/r8a7745.dtsi | 24 +++++++++
> arch/arm64/boot/dts/renesas/r8a7795.dtsi | 93 ++++++++++++++++++++++++++++++++
> arch/arm64/boot/dts/renesas/r8a7796.dtsi | 46 ++++++++++++++++
> 4 files changed, 187 insertions(+)
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org
> 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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