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From: "Krzysztof Wilczyński" <kw@linux.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: kishon@kernel.org, lpieralisi@kernel.org, bhelgaas@google.com,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	robh@kernel.org, vidyas@nvidia.com, vigneshr@ti.com
Subject: Re: [PATCH v5 0/5] PCI: endpoint: Rework the EPC to EPF notification
Date: Tue, 14 Feb 2023 07:51:07 +0900	[thread overview]
Message-ID: <Y+q+2zBWoyXd041n@rocinante> (raw)
In-Reply-To: <20230124071158.5503-1-manivannan.sadhasivam@linaro.org>

Hello,

> During the review of the patch that fixes DBI access in PCI EP, Rob
> suggested [1] using a fixed interface for passing the events from EPC to
> EPF instead of the in-kernel notifiers.
> 
> This series introduces a simple callback based mechanism for passing the
> events from EPC to EPF. This interface is chosen for satisfying the below
> requirements:
> 
> 1. The notification has to reach the EPF drivers without any additional
> latency.
> 2. The context of the caller (EPC) needs to be preserved while passing the
> notifications.
> 
> With the existing notifier mechanism, the 1st case can be satisfied since
> notifiers aren't adding any huge overhead. But the 2nd case is clearly not
> satisfied, because the current atomic notifiers forces the EPF
> notification context to be atomic even though the caller (EPC) may not be
> in atomic context. In the notification function, the EPF drivers are
> required to call several EPC APIs that might sleep and this triggers a
> sleeping in atomic bug during runtime.
> 
> The above issue could be fixed by using a blocking notifier instead of
> atomic, but that proposal was not accepted either [2].
> 
> So instead of working around the issues within the notifiers, let's get rid
> of it and use the callback mechanism.
> 
> NOTE: DRA7xx and TEGRA194 drivers are only compile tested. Testing this series
> on the real platforms is greatly appreciated.
[...]

Applied to pci/endpoint, thank you!

[01/05] PCI: dra7xx: Use threaded IRQ handler for "dra7xx-pcie-main" IRQ
        https://git.kernel.org/pci/pci/c/da87d35a6e51

[02/05] PCI: tegra194: Move dw_pcie_ep_linkup() to threaded IRQ handler
        https://git.kernel.org/pci/pci/c/c2cc5cdda46c

[03/05] PCI: endpoint: Use a separate lock for protecting epc->pci_epf list
        https://git.kernel.org/pci/pci/c/d6dd5bafaabf

[04/05] PCI: endpoint: Use callback mechanism for passing events from EPC to EPF
        https://git.kernel.org/pci/pci/c/838125b07e77

[05/05] PCI: endpoint: Use link_up() callback in place of LINK_UP notifier
        https://git.kernel.org/pci/pci/c/f5edd8715e2e

	Krzysztof

      parent reply	other threads:[~2023-02-13 22:51 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-24  7:11 [PATCH v5 0/5] PCI: endpoint: Rework the EPC to EPF notification Manivannan Sadhasivam
2023-01-24  7:11 ` [PATCH v5 1/5] PCI: dra7xx: Use threaded IRQ handler for "dra7xx-pcie-main" IRQ Manivannan Sadhasivam
2023-01-24  7:11 ` [PATCH v5 2/5] PCI: tegra194: Move dw_pcie_ep_linkup() to threaded IRQ handler Manivannan Sadhasivam
2023-01-24  7:11 ` [PATCH v5 3/5] PCI: endpoint: Use a separate lock for protecting epc->pci_epf list Manivannan Sadhasivam
2023-01-24  7:11 ` [PATCH v5 4/5] PCI: endpoint: Use callback mechanism for passing events from EPC to EPF Manivannan Sadhasivam
2023-01-24  7:11 ` [PATCH v5 5/5] PCI: endpoint: Use link_up() callback in place of LINK_UP notifier Manivannan Sadhasivam
2023-01-24  7:16 ` [PATCH v5 0/5] PCI: endpoint: Rework the EPC to EPF notification Manivannan Sadhasivam
2023-02-13  6:57   ` Manivannan Sadhasivam
2023-02-13 18:32     ` Krzysztof Wilczyński
2023-02-13 22:51 ` Krzysztof Wilczyński [this message]

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