Hi Rob,
Thanks for your reply.
On 01/31/2018 09:50 PM, Rob Herring wrote:
On Wed, Jan 31, 2018 at 1:52 AM, Tomasz Figa <tf...@chromium.org> wrote:
Hi Rob,
On Wed, Jan 31, 2018 at 2:05 AM, Rob Herring <r...@kernel.org> wrote:
On Wed, Jan 24, 2018 at 06:35:11PM +0800, Jeffy Chen wrote:
From: Tomasz Figa <tf...@chromium.org>
Current code relies on master driver enabling necessary clocks before
IOMMU is accessed, however there are cases when the IOMMU should be
accessed while the master is not running yet, for example allocating
V4L2 videobuf2 buffers, which is done by the VB2 framework using DMA
mapping API and doesn't engage the master driver at all.
This patch fixes the problem by letting clocks needed for IOMMU
operation to be listed in Device Tree and making the driver enable them
for the time of accessing the hardware.
Signed-off-by: Jeffy Chen <jeffy.c...@rock-chips.com>
Signed-off-by: Tomasz Figa <tf...@chromium.org>
---
Changes in v5:
Use clk_bulk APIs.
Changes in v4: None
Changes in v3: None
Changes in v2: None
.../devicetree/bindings/iommu/rockchip,iommu.txt | 8 +++
Please split binding patches to a separate patch.
right, i'll do that in the next version.
drivers/iommu/rockchip-iommu.c | 74 ++++++++++++++++++++--
2 files changed, 76 insertions(+), 6 deletions(-)
diff --git a/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
b/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
index 2098f7732264..33dd853359fa 100644
--- a/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
+++ b/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
@@ -14,6 +14,13 @@ Required properties:
"single-master" device, and needs no additional
information
to associate with its master device. See:
Documentation/devicetree/bindings/iommu/iommu.txt
+Optional properties:
+- clocks : A list of master clocks requires for the IOMMU to be accessible
+ by the host CPU. The number of clocks depends on the master
+ block and might as well be zero. See [1] for generic clock
+ bindings description.
Hardware blocks don't have a variable number of clock connections.
I think you underestimate the imagination of hardware designers. :)
Learned long ago to never do that. If there are 2 ways to do
something, they will find a 3rd way.
For Rockchip IOMMU, there is a set of clocks, which all need to be
enabled for IOMMU register access to succeed. The clocks are not
directly fed to the IOMMU, but they are needed for the various buses
and intermediate blocks on the way to the IOMMU to work.
The binding should describe the clock connections, not what clocks a
driver needs (currently). It sounds like a lack of managing bus clocks
to me.
In any case, the binding must be written so it can be verified. If you
can have any number of clocks with any names, there's no point in
documenting.
the rockchip IOMMU is part of the master block in hardware, so it needs
to control the master's power domain and some of the master's clocks
when access it's registers.
and the number of clocks needed here, might be different between each
IOMMUs(according to which master block it belongs), it's a little like
our power domain:
https://elixir.free-electrons.com/linux/latest/source/arch/arm64/boot/dts/rockchip/rk3399.dtsi#L935
i'm not sure how to describe this correctly, is it ok use something like
"the same as it's master block"?
Rob
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