On 05/04/2016 08:40 AM, Thierry Reding wrote:
From: Thierry Reding <treding@xxxxxxxxxx>
Starting with commit 0b52297f2288 ("reset: Add support for shared reset
controls") there is a reference count for reset control assertions. The
goal is to allow resets to be shared by multiple devices and an assert
will take effect only when all instances have asserted the reset.
In order to preserve backwards-compatibility, all reset controls become
exclusive by default. This is to ensure that reset_control_assert() can
immediately assert in hardware.
However, this new behaviour triggers the following warning in the EHCI
driver for Tegra:
...
The reason is that Tegra SoCs have three EHCI controllers, each with a
separate reset line. However the first controller contains UTMI pads
configuration registers that are shared with its siblings and that are
reset as part of the first controller's reset. There is special code in
the driver to assert and deassert this shared reset at probe time, and
it does so irrespective of which controller is probed first to ensure
that these shared registers are reset before any of the controllers are
initialized. Unfortunately this means that if the first controller gets
probed first, it will request its own reset line and will subsequently
request the same reset line again (temporarily) to perform the reset.
This used to work fine before the above-mentioned commit, but now
triggers the new WARN.
Work around this by making sure we reuse the controller's reset if the
controller happens to be the first controller.
diff --git a/drivers/usb/host/ehci-tegra.c b/drivers/usb/host/ehci-tegra.c
@@ -81,15 +81,23 @@ static int tegra_reset_usb_controller(struct platform_device *pdev)
+ bool has_utmi_pad_registers = false;
phy_np = of_parse_phandle(pdev->dev.of_node, "nvidia,phy", 0);
if (!phy_np)
return -ENOENT;
+ if (of_property_read_bool(phy_np, "nvidia,has-utmi-pad-registers"))
+ has_utmi_pad_registers = true;
Isn't that just:
has_utmi_pad_registers = of_property_read_bool(phy_np,
"nvidia,has-utmi-pad-registers");
... and then you can remove " = false" from the declaration too?
if (!usb1_reset_attempted) {
struct reset_control *usb1_reset;
- usb1_reset = of_reset_control_get(phy_np, "utmi-pads");
+ if (!has_utmi_pad_registers)
+ usb1_reset = of_reset_control_get(phy_np, "utmi-pads");
+ else
+ usb1_reset = tegra->rst;
...
usb1_reset_attempted = true;
}
This is a pre-existing issue, but what happens if the probes for two USB
controllers run in parallel; there seems to be missing locking related
to testing/setting usb1_reset_attempted, which could cause multiple
parallel attempts to get the "utmi-pads" reset object, which would
presumably cause essentially the same issue this patch is solving in
other cases?
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