From: Bjorn Helgaas <helgaas@kernel.org>
To: Niklas Cassel <cassel@kernel.org>
Cc: "Manivannan Sadhasivam" <manivannan.sadhasivam@linaro.org>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
"Rob Herring" <robh@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Kishon Vijay Abraham I" <kishon@kernel.org>,
"Thierry Reding" <thierry.reding@gmail.com>,
"Jonathan Hunter" <jonathanh@nvidia.com>,
"Jingoo Han" <jingoohan1@gmail.com>,
linux-pci@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-kernel@vger.kernel.org, mhi@lists.linux.dev,
linux-tegra@vger.kernel.org
Subject: Re: [PATCH v2 10/10] PCI: qcom: Implement shutdown() callback to properly reset the endpoint devices
Date: Tue, 9 Apr 2024 08:31:55 -0500 [thread overview]
Message-ID: <20240409133155.GA2072077@bhelgaas> (raw)
In-Reply-To: <Zg22Dhi2c7U5oqoz@ryzen>
On Wed, Apr 03, 2024 at 10:03:26PM +0200, Niklas Cassel wrote:
> On Wed, Apr 03, 2024 at 07:02:17PM +0530, Manivannan Sadhasivam wrote:
> > On Tue, Apr 02, 2024 at 01:18:54PM +0200, Niklas Cassel wrote:
> > > On Mon, Apr 01, 2024 at 09:20:36PM +0530, Manivannan Sadhasivam wrote:
> > > > PCIe host controller drivers are supposed to properly reset the endpoint
> > > > devices during host shutdown/reboot. Currently, Qcom driver doesn't do
> > > > anything during host shutdown/reboot, resulting in both PERST# and refclk
> > > > getting disabled at the same time. This prevents the endpoint device
> > > > firmware to properly reset the state machine. Because, if the refclk is
> > > > cutoff immediately along with PERST#, access to device specific registers
> > > > within the endpoint will result in a firmware crash.
> > > >
> > > > To address this issue, let's call qcom_pcie_host_deinit() inside the
> > > > shutdown callback, that asserts PERST# and then cuts off the refclk with a
> > > > delay of 1ms, thus allowing the endpoint device firmware to properly
> > > > cleanup the state machine.
> ...
> For a real PCIe card, if you assert + msleep(100) + deassert PERST, surely
> the endpoint is supposed to be in a good/well defined state, regardless if
> he REFCLK was cutoff at the exact time as PERST was asserted or not?
I think this is the key point. This PERST#/REFCLK timing requirement
seems like a defect in the endpoint. I know there's firmware involved
and whatnot, but IMO it's the endpoint's problem to handle these issues
internally.
Bjorn
next prev parent reply other threads:[~2024-04-09 13:31 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-01 15:50 [PATCH v2 00/10] PCI: endpoint: Make host reboot handling more robust Manivannan Sadhasivam
2024-04-01 15:50 ` [PATCH v2 01/10] PCI: qcom-ep: Disable resources unconditionally during PERST# assert Manivannan Sadhasivam
2024-04-01 15:50 ` [PATCH v2 02/10] PCI: endpoint: Decouple EPC and PCIe bus specific events Manivannan Sadhasivam
2024-04-02 0:14 ` Damien Le Moal
2024-04-03 14:26 ` Manivannan Sadhasivam
2024-04-04 2:40 ` Damien Le Moal
2024-04-01 15:50 ` [PATCH v2 03/10] PCI: endpoint: Rename core_init() callback in 'struct pci_epc_event_ops' to init() Manivannan Sadhasivam
2024-04-02 10:52 ` Niklas Cassel
2024-04-03 13:46 ` Manivannan Sadhasivam
2024-04-03 15:51 ` Manivannan Sadhasivam
2024-04-01 15:50 ` [PATCH v2 04/10] PCI: epf-test: Refactor pci_epf_test_unbind() function Manivannan Sadhasivam
2024-04-01 15:50 ` [PATCH v2 05/10] PCI: epf-{mhi/test}: Move DMA initialization to EPC init callback Manivannan Sadhasivam
2024-04-01 15:50 ` [PATCH v2 06/10] PCI: endpoint: Introduce EPC 'deinit' event and notify the EPF drivers Manivannan Sadhasivam
2024-04-01 15:50 ` [PATCH v2 07/10] PCI: dwc: ep: Add a generic dw_pcie_ep_linkdown() API to handle Link Down event Manivannan Sadhasivam
2024-04-02 10:52 ` Niklas Cassel
2024-04-01 15:50 ` [PATCH v2 08/10] PCI: qcom-ep: Use the " Manivannan Sadhasivam
2024-04-01 15:50 ` [PATCH v2 09/10] PCI: epf-test: Handle " Manivannan Sadhasivam
2024-04-01 15:50 ` [PATCH v2 10/10] PCI: qcom: Implement shutdown() callback to properly reset the endpoint devices Manivannan Sadhasivam
2024-04-02 11:18 ` Niklas Cassel
2024-04-03 13:32 ` Manivannan Sadhasivam
2024-04-03 20:03 ` Niklas Cassel
2024-04-09 13:31 ` Bjorn Helgaas [this message]
2024-04-10 10:54 ` Manivannan Sadhasivam
2024-04-10 14:52 ` Niklas Cassel
2024-04-10 21:10 ` Niklas Cassel
2024-04-12 6:32 ` Manivannan Sadhasivam
2024-04-02 9:41 ` [PATCH v2 00/10] PCI: endpoint: Make host reboot handling more robust Niklas Cassel
2024-04-03 13:48 ` Manivannan Sadhasivam
2024-04-08 9:49 ` Niklas Cassel
2024-04-02 10:52 ` Niklas Cassel
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