linux-kernel - Re: [PATCH v3] PCI: j721e: Fix programming sequence of "strap" settings

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Message-ID: <a0e1d273-239b-44e5-8ccc-0ba83b2b5839@ti.com>
Date: Thu, 4 Sep 2025 11:33:00 +0530
From: Siddharth Vadapalli <s-vadapalli@...com>
To: Manivannan Sadhasivam <mani@...nel.org>
CC: Siddharth Vadapalli <s-vadapalli@...com>, <lpieralisi@...nel.org>,
        <kwilczynski@...nel.org>, <robh@...nel.org>, <bhelgaas@...gle.com>,
        <helgaas@...nel.org>, <kishon@...nel.org>, <vigneshr@...com>,
        <stable@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <srk@...com>
Subject: Re: [PATCH v3] PCI: j721e: Fix programming sequence of "strap"
 settings

On Wed, Sep 03, 2025 at 06:51:14PM +0530, Manivannan Sadhasivam wrote:

[...]

> 
> I thought put_noidle() will just reduce the refcount and not invoke the
> idle/suspend callbacks, but I seem to be wrong here.
> 
> Anyway, I guess we have no option here other than to drop the
> pm_runtime_put_noidle() call. This will keep refcount as 1 and will prevent the
> parent (genpd) to not enter runtime suspend, but we have to live with it (this
> was also the previous beahvior as well).
> 
> Btw, pm_runtime_set_active/enable change belongs to a separate patch.

I will work on and post the v4 patch with the following change:
- The commit message and the comment in the code will be updated to
  indicate that the runtime PM APIs are used to cause 'genpd' to power off
  and power on the controller.

I assume that the driver changes can remain as they are in this patch given
that the existing behavior has to be preserved. As j721e_pcie_ctrl_init()
programs the strap settings, powering off the controller via
pm_runtime_put_sync() and powering it on via pm_runtime_get_sync() shall
be implemented within j721e_pcie_ctrl_init() itself leaving the rest of the
probe function as-is. To summarize, the driver changes will be:

	j721e_pcie_ctrl_init()
		...Existing code...
	+	Add pm_runtime_put_sync() here to power off controller
		...Existing code to program strap settings...
	+	Add pm_runtime_get_sync() here to power on controller
		...Existing code...

Please let me know what you think.

Regards,
Siddharth.