Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 51985C433F5 for ; Tue, 23 Nov 2021 12:49:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237162AbhKWMxB (ORCPT ); Tue, 23 Nov 2021 07:53:01 -0500 Received: from sibelius.xs4all.nl ([83.163.83.176]:63191 "EHLO sibelius.xs4all.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236671AbhKWMwn (ORCPT ); Tue, 23 Nov 2021 07:52:43 -0500 Received: from localhost (bloch.sibelius.xs4all.nl [local]) by bloch.sibelius.xs4all.nl (OpenSMTPD) with ESMTPA id 6fa1d3a8; Tue, 23 Nov 2021 13:49:32 +0100 (CET) Date: Tue, 23 Nov 2021 13:49:32 +0100 (CET) From: Mark Kettenis To: Marc Zyngier Cc: pali@kernel.org, luca@lucaceresoli.net, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, kernel-team@android.com, alyssa@rosenzweig.io, lorenzo.pieralisi@arm.com, bhelgaas@google.com, joey.gouly@arm.com In-Reply-To: <87k0gzcb6d.wl-maz@kernel.org> (message from Marc Zyngier on Tue, 23 Nov 2021 12:24:10 +0000) Subject: Re: [PATCH v2] PCI: apple: Follow the PCIe specifications when resetting the port References: <20211122104156.518063-1-maz@kernel.org> <20211122120347.6qyiycqqjkgqvtta@pali> <87zgpw5jza.wl-maz@kernel.org> <87k0gzcb6d.wl-maz@kernel.org> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Message-ID: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Date: Tue, 23 Nov 2021 12:24:10 +0000 > From: Marc Zyngier > > On Mon, 22 Nov 2021 21:50:48 +0000, > Mark Kettenis wrote: > > > > > Date: Mon, 22 Nov 2021 14:43:37 +0000 > > > From: Marc Zyngier > > > > > > On Mon, 22 Nov 2021 12:03:47 +0000, > > > Pali Rohár wrote: > > > > > > > > On Monday 22 November 2021 10:41:56 Marc Zyngier wrote: > > > > > While the Apple PCIe driver works correctly when directly booted > > > > > from the firmware, it fails to initialise when the kernel is booted > > > > > from a bootloader using PCIe such as u-boot. > > > > > > > > > > That's beacuse we're missing a proper reset of the port (we only > > > > > clear the reset, but never assert it). > > > > > > > > > > The PCIe spec requirements are two-fold: > > > > > > > > > > - #PERST must be asserted before setting up the clocks, and > > > > > stay asserted for at least 100us (Tperst-clk). > > > > > > > > > > - Once #PERST is deasserted, the OS must wait for at least 100ms > > > > > "from the end of a Conventional Reset" before we can start talking > > > > > to the devices > > > > > > > > > > Implementing this results in a booting system. > > > > > > > > > > Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up") > > > > > Signed-off-by: Marc Zyngier > > > > > Cc: Alyssa Rosenzweig > > > > > Cc: Lorenzo Pieralisi > > > > > Cc: Bjorn Helgaas > > > > > Cc: Pali Rohár > > > > > > > > Looks good, but see comment below. > > > > > > > > Acked-by: Pali Rohár > > > > > > Thanks for that. > > > > > > > > > > > > --- > > > > > drivers/pci/controller/pcie-apple.c | 10 ++++++++++ > > > > > 1 file changed, 10 insertions(+) > > > > > > > > > > diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c > > > > > index 1bf4d75b61be..957960a733c4 100644 > > > > > --- a/drivers/pci/controller/pcie-apple.c > > > > > +++ b/drivers/pci/controller/pcie-apple.c > > > > > @@ -539,13 +539,23 @@ static int apple_pcie_setup_port(struct apple_pcie *pcie, > > > > > > > > > > rmw_set(PORT_APPCLK_EN, port->base + PORT_APPCLK); > > > > > > > > > > + /* Engage #PERST before setting up the clock */ > > > > > + gpiod_set_value(reset, 0); > > > > > + > > > > > ret = apple_pcie_setup_refclk(pcie, port); > > > > > if (ret < 0) > > > > > return ret; > > > > > > > > > > + /* The minimal Tperst-clk value is 100us (PCIe CMS r2.0, 2.6.2) */ > > > > > + usleep_range(100, 200); > > > > > + > > > > > + /* Deassert #PERST */ > > > > > rmw_set(PORT_PERST_OFF, port->base + PORT_PERST); > > > > > gpiod_set_value(reset, 1); > > > > > > > > + Luca > > > > > > > > Just one comment. PERST# (PCIe Reset) is active-low signal. De-asserting > > > > means to really set value to 1. > > > > > > > > But there was a discussion that de-asserting should be done by call: > > > > gpiod_set_value(reset, 0); > > > > > > > > https://lore.kernel.org/linux-pci/51be082a-ff10-8a19-5648-f279aabcac51@lucaceresoli.net/ > > > > > > > > Could we make this new pcie-apple.c driver to use gpiod_set_value(reset, 0) > > > > for de-asserting, like in other drivers? > > > > > > I guess it depends whether you care about the assertion or the signal > > > itself. I think we may have a bug in the way the GPIOs are handled at > > > the moment, as it makes no difference whether I register the GPIO are > > > active high or active low... > > > > That's unfortunate. But maybe that's an opportunity to fix the > > devicetree to use GPIO_ACTIVE_LOW for these GPIOs? > > Indeed. The following hack does the right thing, and I can then > reverse the polarity of the reset in the Linux driver. Of course, it > breaks u-boot at the same time (and I suspect OpenBSD would be equally > affected). As I said in my other reply (that clearly crossed this message) the U-Boot PCIe driver has not been upstreamed yet. OpenBSD (and also NetBSD) rely on the configuration done by U-Boot and don't mess with the reset GPIO at this moment. > So if we are going down that road, we may need a flag day where all > the moving parts change. I don't really mind not being able to boot > older kernels, but this goes beyond Linux at this point. So I don't think this is needed. The earlier we fix this the better! > diff --git a/arch/arm64/boot/dts/apple/t8103.dtsi b/arch/arm64/boot/dts/apple/t8103.dtsi > index d2e9afde3729..cad1ab920304 100644 > --- a/arch/arm64/boot/dts/apple/t8103.dtsi > +++ b/arch/arm64/boot/dts/apple/t8103.dtsi > @@ -10,6 +10,7 @@ > #include > #include > #include > +#include > > / { > compatible = "apple,t8103", "apple,arm-platform"; > @@ -293,7 +294,7 @@ pcie0: pcie@690000000 { > port00: pci@0,0 { > device_type = "pci"; > reg = <0x0 0x0 0x0 0x0 0x0>; > - reset-gpios = <&pinctrl_ap 152 0>; > + reset-gpios = <&pinctrl_ap 152 GPIO_ACTIVE_LOW>; > max-link-speed = <2>; > > #address-cells = <3>; > @@ -313,7 +314,7 @@ port00: pci@0,0 { > port01: pci@1,0 { > device_type = "pci"; > reg = <0x800 0x0 0x0 0x0 0x0>; > - reset-gpios = <&pinctrl_ap 153 0>; > + reset-gpios = <&pinctrl_ap 153 GPIO_ACTIVE_LOW>; > max-link-speed = <2>; > > #address-cells = <3>; > @@ -333,7 +334,7 @@ port01: pci@1,0 { > port02: pci@2,0 { > device_type = "pci"; > reg = <0x1000 0x0 0x0 0x0 0x0>; > - reset-gpios = <&pinctrl_ap 33 0>; > + reset-gpios = <&pinctrl_ap 33 GPIO_ACTIVE_LOW>; > max-link-speed = <1>; > > #address-cells = <3>; > > -- > Without deviation from the norm, progress is not possible. > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel