Re: [PATCH 3/5] PCI: dwc: ep: Add a generic dw_pcie_ep_linkdown() API to handle Link Down event

From: Niklas Cassel <cassel@kernel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: "Vignesh Raghavendra" <vigneshr@ti.com>,
	"Siddharth Vadapalli" <s-vadapalli@ti.com>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Rob Herring" <robh@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Richard Zhu" <hongxing.zhu@nxp.com>,
	"Lucas Stach" <l.stach@pengutronix.de>,
	"Shawn Guo" <shawnguo@kernel.org>,
	"Sascha Hauer" <s.hauer@pengutronix.de>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>,
	"Fabio Estevam" <festevam@gmail.com>,
	"Minghuan Lian" <minghuan.Lian@nxp.com>,
	"Mingkai Hu" <mingkai.hu@nxp.com>, "Roy Zang" <roy.zang@nxp.com>,
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	"Jingoo Han" <jingoohan1@gmail.com>,
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	"Yoshihiro Shimoda" <yoshihiro.shimoda.uh@renesas.com>,
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	"Jonathan Hunter" <jonathanh@nvidia.com>,
	"Kunihiko Hayashi" <hayashi.kunihiko@socionext.com>,
	"Masami Hiramatsu" <mhiramat@kernel.org>,
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Subject: Re: [PATCH 3/5] PCI: dwc: ep: Add a generic dw_pcie_ep_linkdown() API to handle Link Down event
Date: Fri, 7 Jun 2024 11:21:44 +0200	[thread overview]
Message-ID: <ZmLRKJ76esDBgYW1@ryzen.lan> (raw)
In-Reply-To: <20240606-pci-deinit-v1-3-4395534520dc@linaro.org>

On Thu, Jun 06, 2024 at 12:56:36PM +0530, Manivannan Sadhasivam wrote:
> As per the PCIe base spec r5.0, section 5.2, Link Down event can happen
> under any of the following circumstances:
> 
> 1. Fundamental/Hot reset
> 2. Link disable transmission by upstream component
> 3. Moving from L2/L3 to L0
> 
> In those cases, Link Down causes some non-sticky DWC registers to loose the
> state (like REBAR, etc...). So the drivers need to reinitialize them to
> function properly once the link comes back again.
> 
> This is not a problem for drivers supporting PERST# IRQ, since they can
> reinitialize the registers in the PERST# IRQ callback. But for the drivers
> not supporting PERST#, there is no way they can reinitialize the registers
> other than relying on Link Down IRQ received when the link goes down. So
> let's add a DWC generic API dw_pcie_ep_linkdown() that reinitializes the
> non-sticky registers and also notifies the EPF drivers about link going
> down.
> 
> This API can also be used by the drivers supporting PERST# to handle the
> scenario (2) mentioned above.
> 
> NOTE: For the sake of code organization, move the dw_pcie_ep_linkup()
> definition just above dw_pcie_ep_linkdown().
> 
> Reviewed-by: Niklas Cassel <cassel@kernel.org>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---

Like Siddharth reported, this patch is already in pci/next.