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Date: Fri, 16 Feb 2024 12:09:17 +0100
Message-Id: <CZ6GG6OQUJTX.2OM5TC9YLOAXV@bootlin.com>
From: =?utf-8?q?Th=C3=A9o_Lebrun?= <theo.lebrun@bootlin.com>
Subject: Re: [PATCH v3 18/18] PCI: j721e: add suspend and resume support
Cc: "Linus Walleij" <linus.walleij@linaro.org>, "Bartosz Golaszewski"
 <brgl@bgdev.pl>, "Andy Shevchenko" <andy@kernel.org>, "Tony Lindgren"
 <tony@atomide.com>, "Haojian Zhuang" <haojian.zhuang@linaro.org>, "Vignesh
 R" <vigneshr@ti.com>, "Aaro Koskinen" <aaro.koskinen@iki.fi>, "Janusz
 Krzysztofik" <jmkrzyszt@gmail.com>, "Andi Shyti" <andi.shyti@kernel.org>,
 "Peter Rosin" <peda@axentia.se>, "Vinod Koul" <vkoul@kernel.org>, "Kishon
 Vijay Abraham I" <kishon@kernel.org>, "Philipp Zabel"
 <p.zabel@pengutronix.de>, "Lorenzo Pieralisi" <lpieralisi@kernel.org>,
 =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= <kw@linux.com>, "Rob Herring"
 <robh@kernel.org>, "Bjorn Helgaas" <bhelgaas@google.com>,
 <linux-gpio@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
 <linux-arm-kernel@lists.infradead.org>, <linux-omap@vger.kernel.org>,
 <linux-i2c@vger.kernel.org>, <linux-phy@lists.infradead.org>,
 <linux-pci@vger.kernel.org>, <gregory.clement@bootlin.com>,
 <thomas.petazzoni@bootlin.com>, <u-kumar1@ti.com>
To: "Siddharth Vadapalli" <s-vadapalli@ti.com>, "Thomas Richard"
 <thomas.richard@bootlin.com>
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References: <20240102-j7200-pcie-s2r-v3-0-5c2e4a3fac1f@bootlin.com>
 <20240102-j7200-pcie-s2r-v3-18-5c2e4a3fac1f@bootlin.com>
 <aa791703-81d8-420c-ba35-c8fd08bc3f07@ti.com>
In-Reply-To: <aa791703-81d8-420c-ba35-c8fd08bc3f07@ti.com>
X-GND-Sasl: theo.lebrun@bootlin.com

Hello,

On Fri Feb 16, 2024 at 11:48 AM CET, Siddharth Vadapalli wrote:
> On 24/02/15 04:18PM, Thomas Richard wrote:
> > From: Th=C3=A9o Lebrun <theo.lebrun@bootlin.com>
> >=20
> > Add suspend and resume support. Only the rc mode is supported.
> >=20
> > During the suspend stage PERST# is asserted, then deasserted during the
> > resume stage.
>
> Wouldn't this imply that the Endpoint device will be reset and therefore
> lose context? Or is it expected that the driver corresponding to the
> Endpoint Function in Linux will restore the state on resume, post reset?

This does imply exactly that. Endpoint driver must be able to restore
context anyway, as system-wide suspend could mean lost power to PCI RC
controller (eg suspend-to-RAM) or PCI rails (dependent on hardware).

Thanks,

--
Th=C3=A9o Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com