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

From: Ilia Mirkin <imirkin@alum.mit.edu>
To: Ansuel Smith <ansuelsmth@gmail.com>
Cc: linux-arm-msm@vger.kernel.org, Linux PCI <linux-pci@vger.kernel.org>
Subject: Regression with "PCI: qcom: Add support for tx term offset for rev 2.1.0"
Date: Sun, 6 Sep 2020 18:58:37 -0400	[thread overview]
Message-ID: <CAKb7UvhqZMcL3UNbK-6ZG9LJddCmoL0paYsRx6+5bVKDQpAjmQ@mail.gmail.com> (raw)

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,

Ilia Mirkin
imirkin@alum.mit.edu