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

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Message-ID: <578e5125-21d8-40c8-aaeb-389599cdd32b@ti.com>
Date: Mon, 8 Sep 2025 13:36:09 +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 Mon, Sep 08, 2025 at 12:58:51PM +0530, Manivannan Sadhasivam wrote:
> On Thu, Sep 04, 2025 at 11:33:00AM GMT, Siddharth Vadapalli wrote:
> > 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.
> 
> I would've preferred changing the runtime PM calls as I suggested initially, but
> still we would keep it incremented which brings the net effect to the same.
> 
> So you can drop my initial comment and post just this patch with improved patch
> description.

Thank you for the clarification. I will implement the above in the v4
patch.

Regards,
Siddharth.