linux-kernel - Re: [PATCH v2 2/2] PCI: starfive: Simplify event doorbell bitmap initialization in pcie-starfive

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Message-ID: <ck6a66u3cn4uzwnz7z3xjoz5rorli7eww4lfzbjxmntbpbnzgt@dg2sfkhw4x4z>
Date: Sat, 19 Apr 2025 16:02:02 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Anand Moon <linux.amoon@...il.com>
Cc: Daire McNamara <daire.mcnamara@...rochip.com>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczyński <kw@...ux.com>, 
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Kevin Xie <kevin.xie@...rfivetech.com>, Conor Dooley <conor.dooley@...rochip.com>, 
	Minda Chen <minda.chen@...rfivetech.com>, Mason Huo <mason.huo@...rfivetech.com>, 
	"open list:PCI DRIVER FOR PLDA PCIE IP" <linux-pci@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] PCI: starfive: Simplify event doorbell bitmap
 initialization in pcie-starfive

On Sun, Mar 16, 2025 at 10:42:46PM +0530, Anand Moon wrote:
> The events_bitmap initialization in starfive_pcie_probe() previously
> masked out the PLDA_AXI_DOORBELL and PLDA_PCIE_DOORBELL events.
> 
> These masking has been removed, allowing these events to be included
> in the bitmap. With this change ensures that all interrupt events are
> properly accounted for and may be necessary for handling doorbell
> events in certain use cases.
> 
> PCIe Doorbell Events: These are typically used to notify a device about
> an event or to trigger an action. For example, a host system can write
> to a doorbell register on a PCIe device to signal that new data is
> available or that an operation should start12.
> 
> AXI-PCIe Bridge: This bridge acts as a protocol converter between AXI
> (Advanced eXtensible Interface) and PCIe (Peripheral Component Interconnect
> Express) domains. It allows transactions to be converted and communicated
> between these two different protocols3.
> 

Are these events used in the driver for any purpose? Others have mentioned a
potential irq storm issue with these interrupts also. So unless you want to
enable these events for a specific purpose/usecase, it is better to keep them
masked out.

- Mani

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