Re: [PATCH 4/9] PCI: mvebu: add support for reset on GPIO

From: Sebastian Hesselbarth
Date: Tue Aug 13 2013 - 05:19:18 EST

[Added DT maintainers directly for a question below]

On 08/13/13 02:56, Kumar Gala wrote:
On Aug 12, 2013, at 1:46 PM, Sebastian Hesselbarth wrote:

This patch adds a check for DT passed reset-gpios property and deasserts/
asserts reset pin on probe/remove with configurable delay. Corresponding
binding documentation is also updated.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@xxxxxxxxx>
diff --git a/Documentation/devicetree/bindings/pci/mvebu-pci.txt b/Documentation/devicetree/bindings/pci/mvebu-pci.txt
index 638673a..f2fa261 100644
--- a/Documentation/devicetree/bindings/pci/mvebu-pci.txt
+++ b/Documentation/devicetree/bindings/pci/mvebu-pci.txt
@@ -76,6 +76,8 @@ and the following optional properties:
- marvell,pcie-lane: the physical PCIe lane number, for ports having
multiple lanes. If this property is not found, we assume that the
value is 0.
+- reset-gpios: optional gpio to PERST#
+- reset-delay-ms: delay in ms to wait after reset de-assertion

Both of these should probably be marvell,reset...


as Thomas already mentioned, non-prefixed "foo-gpios" are quite common.
As reset gpios are likely to be common among SoC pci controller setups,
I though I'd stick with the non-prefixed property. But I have no strong
opinion about it - but let's see how DT jurisdiction will vote :)

Does reset-delay-ms vary per board? I can't remember where the
discussion got to about configuration info.

Hmm, for Dove SoC, I only have one board to test - but the driver
currently is for 4 different SoCs. I just did some quick evaluation
of the reset delay required to bring up the device on the D3Plug.
Using 10ms was too short, 20ms worked.

I guess there will be other SoC/boards requiring different delays
but I am fine with hardcoded 20ms and re-introduce reset-delay property
only if it is really required. The driver's default is 20ms anyway.


It's usually good to update example to show all optional properties.

Ok, will add the properties to one of the example ports.



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