linux-kernel - Re: [PATCH v3] PCI: starfive: Enable PCIe controller's runtime PM before probing host bridge

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Message-ID: <20241014180841.GA613986@bhelgaas>
Date: Mon, 14 Oct 2024 13:08:41 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Mayank Rana <quic_mrana@...cinc.com>, kevin.xie@...rfivetech.com,
	lpieralisi@...nel.org, kw@...ux.com, robh@...nel.org,
	bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, quic_krichai@...cinc.com,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH v3] PCI: starfive: Enable PCIe controller's runtime PM
 before probing host bridge

On Mon, Oct 14, 2024 at 11:18:17PM +0530, Manivannan Sadhasivam wrote:
> On Mon, Oct 14, 2024 at 12:23:21PM -0500, Bjorn Helgaas wrote:
> > On Mon, Oct 14, 2024 at 09:26:07AM -0700, Mayank Rana wrote:
> > > PCIe controller device (i.e. PCIe starfive device) is parent to PCIe host
> > > bridge device. To enable runtime PM of PCIe host bridge device (child
> > > device), it is must to enable parent device's runtime PM to avoid seeing
> > > the below warning from PM core:
> > > 
> > > pcie-starfive 940000000.pcie: Enabling runtime PM for inactive device
> > > with active children
> > > 
> > > Fix this issue by enabling starfive pcie controller device's runtime PM
> > > before calling pci_host_probe() in plda_pcie_host_init().
> > > 
> > > Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> > > Signed-off-by: Mayank Rana <quic_mrana@...cinc.com>
> > > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > 
> > I want this in the same series as Krishna's patch to turn on runtime
> > PM of host bridges.  That's how I know they need to be applied in
> > order.  If they're not in the same series, they're likely to be
> > applied out of order.
> 
> There is no harm in applying this patch on its own. It fixes a legit
> issue of enabling the parent runtime PM before the child as required
> by the PM core. Rest of the controller drivers follow the same
> pattern.
> 
> I fail to understand why you want this to be combined with Krishna's
> patch. That patch is only a trigger, but even without that patch the
> issue still exists (not user visible ofc).

I don't want it *combined* with Krishna's patch.

I want this applied *before* Krishna's patch because if we apply
Krishna's patch first, we have some interval where we report the
"Enabling runtime PM for inactive device with active children" error.

Bjorn