linux-kernel - Re: [PATCH] Revert "PCI: dwc: Wait for link up only if link is started"

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Date: Fri, 19 Jan 2024 13:10:30 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Ajay Agarwal <ajayagarwal@...gle.com>
Cc: Johan Hovold <johan@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Jingoo Han <jingoohan1@...il.com>,
	Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bjorn Andersson <quic_bjorande@...cinc.com>,
	Sajid Dalvi <sdalvi@...gle.com>
Subject: Re: [PATCH] Revert "PCI: dwc: Wait for link up only if link is
 started"

On Fri, Jan 12, 2024 at 03:30:15PM +0530, Ajay Agarwal wrote:

[...]

> > No, IMO the offending commit was wrong in serving its purpose so a revert makes
> > sense. Because, if the intention was to reduce the boot delay then it did not
> > fix that because dw_pcie_wait_for_link() is still called from intel-gw's
> > host_init() callback. You just skipped another instance which is there in
> > dw_pcie_host_init().
> > 
> > So to fix this issue properly intel-gw needs to do 2 things:
> > 
> > 1. Move the ltssm_enable to start_link() callback and get rid of
> > dw_pcie_wait_for_link() from its host_init() callback. If there is any special
> > reason to not do this way, please explain.
> > 
> > 2. Enable async probe so that other drivers can continue probing while this
> > driver waits for the link to be up. This will almost make the delay negligible.
> > 
> > The above 2 should be done in separate patches.
> > 
> > - Mani
> >
> Mani, the intention is not to fix the intel-gw driver in any manner. It
> calls dw_pcie_wait_for_link explicitly in the probe path and checks for
> the error as well. So it has to live with the delay and the probe
> failure if the link does not come up.
> 
> My intention is just to get rid of the 1 sec delay for the drivers that
> do not define the start_link callback, and hence do not expect that the
> link will come up during probe anyway.
> 

Ok, this clarifies, thanks.

- Mani

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