linux-kernel - Re: [PATCH v2 1/2] PCI: qcom: Skip wait for link up if global IRQ handler is present

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Message-ID: <20240930170129.GA179772@bhelgaas>
Date: Mon, 30 Sep 2024 12:01:29 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Krishna chaitanya chundru <quic_krichai@...cinc.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	quic_vbadigan@...cinc.com, quic_ramkri@...cinc.com,
	quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
	quic_vpernami@...cinc.com, quic_mrana@...cinc.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 1/2] PCI: qcom: Skip wait for link up if global IRQ
 handler is present

On Mon, Sep 30, 2024 at 09:49:10AM +0200, Manivannan Sadhasivam wrote:
> On Fri, Sep 20, 2024 at 03:47:59PM +0530, Krishna chaitanya chundru wrote:
> 
> Subject should be modified to reflect the fact that the link up is skipped in
> the dwc driver.
> 
> PCI: dwc: Skip waiting for link up if vendor drivers can detect Link up event
> 
> > In cases where a global IRQ handler is present to manage link up
> > interrupts, it may not be necessary to wait for the link to be up
> > during PCI initialization which optimizes the bootup time.
> 
> How about,
> 
> "If the vendor drivers can detect the Link up event using mechanisms
> such as Link up IRQ, then waiting for Link up during probe is not
> needed. So let's skip waiting for link to be up if the driver
> supports 'linkup_irq'.

I avoid the "let's do X" structure because "let's do" is a proposal.
The patch actually *does* it, so it's more than a proposal.

Also, it would be helpful to extend this with a note about *why* we
can avoid waiting, i.e., if we can be notified when the link comes up,
we can enumerate downstream devices then instead of waiting here.

I suppose the "global" name is already set by DTs, but the name seems
far too general to me.

Bjorn