linux-kernel - Re: [PATCH v2] PCI: cadence: Fix Gen2 Link Retraining process

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Message-ID: <20230329170814.GA3067800@bhelgaas>
Date:   Wed, 29 Mar 2023 12:08:14 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Raghavendra, Vignesh" <vigneshr@...com>
Cc:     Siddharth Vadapalli <s-vadapalli@...com>, tjoseph@...ence.com,
        lpieralisi@...nel.org, robh@...nel.org, kw@...ux.com,
        bhelgaas@...gle.com, nadeem@...ence.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        srk@...com, nm@...com
Subject: Re: [PATCH v2] PCI: cadence: Fix Gen2 Link Retraining process

On Wed, Mar 29, 2023 at 08:11:25PM +0530, Raghavendra, Vignesh wrote:
> Hi Lorenzo, Bjorn,
> 
> On 3/15/2023 12:38 PM, Siddharth Vadapalli wrote:
> > The Link Retraining process is initiated to account for the Gen2 defect in
> > the Cadence PCIe controller in J721E SoC. The errata corresponding to this
> > is i2085, documented at:
> > https://www.ti.com/lit/er/sprz455c/sprz455c.pdf
> > 
> > The existing workaround implemented for the errata waits for the Data Link
> > initialization to complete and assumes that the link retraining process
> > at the Physical Layer has completed. However, it is possible that the
> > Physical Layer training might be ongoing as indicated by the
> > PCI_EXP_LNKSTA_LT bit in the PCI_EXP_LNKSTA register.
> > 
> > Fix the existing workaround, to ensure that the Physical Layer training
> > has also completed, in addition to the Data Link initialization.
> > 
> > Fixes: 4740b969aaf5 ("PCI: cadence: Retrain Link to work around Gen2 training defect")
> > Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>
> > Reviewed-by: Vignesh Raghavendra <vigneshr@...com>
> > ---
> > Changes from v1:
> > 1. Collect Reviewed-by tag from Vignesh Raghavendra.
> > 2. Rebase on next-20230315.
> > 
> > v1:
> > https://lore.kernel.org/r/20230102075656.260333-1-s-vadapalli@ti.com
> > 
> >  .../controller/cadence/pcie-cadence-host.c    | 27 +++++++++++++++++++
> >  1 file changed, 27 insertions(+)
> 
> Wondering do one of you be pulling this patch in? This patch was never
> picked for 6.3-rc1 merge cycle... Just want to make sure
> pcie-cadence*.c and pci-j721e.c patches have a path to reach pci tree.

Yes, Lorenzo or Krzysztof will likely pick this up.  I think Lorenzo
is out of the office this week.

Drive-by comment: the current patch doesn't seem to give any
indication to the user when cdns_pcie_host_training_complete() times
out.  Is that timeout potentially of interest to a user?  Should there
be a log message there?

Bjorn