R: Regression with "PCI: qcom: Add support for tx term offset for rev 2.1.0"

[<ansuelsmth@gmail.com>]

> -----Messaggio originale-----
> Da: Ilia Mirkin <imirkin@alum.mit.edu>
> Inviato: lunedì 7 settembre 2020 00:59
> A: Ansuel Smith <ansuelsmth@gmail.com>
> Cc: linux-arm-msm@vger.kernel.org; Linux PCI <linux-pci@vger.kernel.org>
> Oggetto: Regression with "PCI: qcom: Add support for tx term offset for rev
> 2.1.0"
> 
> Hi Ansuel,
> 
> I'm on an ifc6410 (APQ8064), and the latest v5.9-rc's hang during PCIe
> init. I just get:
> 
> [    1.191861] qcom-pcie 1b500000.pci: host bridge /soc/pci@1b500000
> ranges:
> [    1.197756] qcom-pcie 1b500000.pci:       IO
> 0x000fe00000..0x000fefffff -> 0x0000000000
> [    1.205625] qcom-pcie 1b500000.pci:      MEM
> 0x0008000000..0x000fdfffff -> 0x0008000000
> 
> and then it hangs forever. On a working kernel, the next message is e.g.
> 
> [    6.737388] qcom-pcie 1b500000.pci: Link up
> 
> A bisect led to
> 
> $ git bisect good
> de3c4bf648975ea0b1d344d811e9b0748907b47c is the first bad commit
> commit de3c4bf648975ea0b1d344d811e9b0748907b47c
> Author: Ansuel Smith <ansuelsmth@gmail.com>
> Date:   Mon Jun 15 23:06:04 2020 +0200
> 
>     PCI: qcom: Add support for tx term offset for rev 2.1.0
> 
>     Add tx term offset support to pcie qcom driver need in some revision of
>     the ipq806x SoC. Ipq8064 needs tx term offset set to 7.
> 
>     Link: https://lore.kernel.org/r/20200615210608.21469-9-
> ansuelsmth@gmail.com
>     Fixes: 82a823833f4e ("PCI: qcom: Add Qualcomm PCIe controller driver")
>     Signed-off-by: Sham Muthayyan <smuthayy@codeaurora.org>
>     Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
>     Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
>     Acked-by: Stanimir Varbanov <svarbanov@mm-sol.com>
>     Cc: stable@vger.kernel.org # v4.5+
> 
>  drivers/pci/controller/dwc/pcie-qcom.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> 
> And indeed reverting this commit on top of v5.9-rc3 gets back to a
> working system. I have no idea what PHY_REFCLK_USE_PAD is, but it
> seems like clearing it is messing things up for me. (As everything
> else seems like it should be identical for me.)
> 
> Let me know if you want me to test anything, or if the best path is to
> just revert for now.
> 
> Cheers,
> 

Thanks for the report. Can you confirm that by only removing 
PHY_REFCLK_USE_PAD the problem is fixed? Wonder if it's better to
just make a patch to restrict the padding to only ipq806x and backport that.
(or revert and repush a better patch). What do you think?

> Ilia Mirkin
> imirkin@alum.mit.edu