Re: [PATCH v2] PCI: qcom-ep: Enable controller resources like PHY only after refclk is available

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Aug 28, 2024 at 07:31:08PM +0530, Manivannan Sadhasivam wrote:
> qcom_pcie_enable_resources() is called by qcom_pcie_ep_probe() and it
> enables the controller resources like clocks, regulator, PHY. On one of the
> new unreleased Qcom SoC, PHY enablement depends on the active refclk. And
> on all of the supported Qcom endpoint SoCs, refclk comes from the host
> (RC). So calling qcom_pcie_enable_resources() without refclk causes the
> whole SoC crash on the new SoC.
> 
> qcom_pcie_enable_resources() is already called by
> qcom_pcie_perst_deassert() when PERST# is deasserted, and refclk is
> available at that time.
> 
> Hence, remove the unnecessary call to qcom_pcie_enable_resources() from
> qcom_pcie_ep_probe() to prevent the crash.
> 
> Fixes: 869bc5253406 ("PCI: dwc: ep: Fix DBI access failure for drivers requiring refclk from host")
> Tested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---
> 
> Changes in v2:
> 
> - Changed the patch description to mention the crash clearly as suggested by
>   Bjorn

Clearly mentioning the crash as rationale for the change is *part* of
what I was looking for.

The rest, just as important, is information about what sort of crash
this is, because I hope and suspect the crash is recoverable, and we
*should* recover from it because PERST# may occur at arbitrary times,
so trying to avoid it is never going to be reliable.

Bjorn