From 7cc9ca5a994c90fa771135e50b7a9cb99a65aa1d Mon Sep 17 00:00:00 2001 From: Thierry Reding Date: Thu, 26 May 2016 17:23:30 +0200 Subject: [PATCH] usb: host: ehci-tegra: Avoid getting the same reset twice 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: [ 3.365019] ------------[ cut here ]------------ [ 3.369639] WARNING: CPU: 0 PID: 1 at drivers/reset/core.c:187 __of_reset_control_get+0x16c/0x23c [ 3.382151] Modules linked in: [ 3.385214] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0-rc6-next-20160503 #140 [ 3.392769] Hardware name: NVIDIA Tegra SoC (Flattened Device Tree) [ 3.399046] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [ 3.406787] [] (show_stack) from [] (dump_stack+0x90/0xa4) [ 3.414007] [] (dump_stack) from [] (__warn+0xe8/0x100) [ 3.420964] [] (__warn) from [] (warn_slowpath_null+0x20/0x28) [ 3.428525] [] (warn_slowpath_null) from [] (__of_reset_control_get+0x16c/0x23c) [ 3.437648] [] (__of_reset_control_get) from [] (tegra_ehci_probe+0x394/0x518) [ 3.446600] [] (tegra_ehci_probe) from [] (platform_drv_probe+0x4c/0xb0) [ 3.455029] [] (platform_drv_probe) from [] (driver_probe_device+0x1ec/0x330) [ 3.463892] [] (driver_probe_device) from [] (__driver_attach+0xb8/0xbc) [ 3.472320] [] (__driver_attach) from [] (bus_for_each_dev+0x68/0x9c) [ 3.480489] [] (bus_for_each_dev) from [] (bus_add_driver+0x1a0/0x218) [ 3.488743] [] (bus_add_driver) from [] (driver_register+0x78/0xf8) [ 3.496738] [] (driver_register) from [] (do_one_initcall+0x40/0x170) [ 3.504909] [] (do_one_initcall) from [] (kernel_init_freeable+0x158/0x1f8) [ 3.513600] [] (kernel_init_freeable) from [] (kernel_init+0x8/0x114) [ 3.521770] [] (kernel_init) from [] (ret_from_fork+0x14/0x3c) [ 3.529361] ---[ end trace 4bda87dbe4ecef8a ]--- 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. Cc: Philipp Zabel Cc: Hans de Goede Reviewed-by: Philipp Zabel Signed-off-by: Thierry Reding Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ehci-tegra.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/drivers/usb/host/ehci-tegra.c b/drivers/usb/host/ehci-tegra.c index c1c1024a054c..9a3d7db5be57 100644 --- 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) struct usb_hcd *hcd = platform_get_drvdata(pdev); struct tegra_ehci_hcd *tegra = (struct tegra_ehci_hcd *)hcd_to_ehci(hcd)->priv; + 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; + 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; + if (IS_ERR(usb1_reset)) { dev_warn(&pdev->dev, "can't get utmi-pads reset from the PHY\n"); @@ -99,13 +107,15 @@ static int tegra_reset_usb_controller(struct platform_device *pdev) reset_control_assert(usb1_reset); udelay(1); reset_control_deassert(usb1_reset); + + if (!has_utmi_pad_registers) + reset_control_put(usb1_reset); } - reset_control_put(usb1_reset); usb1_reset_attempted = true; } - if (!of_property_read_bool(phy_np, "nvidia,has-utmi-pad-registers")) { + if (!has_utmi_pad_registers) { reset_control_assert(tegra->rst); udelay(1); reset_control_deassert(tegra->rst); -- 2.20.1