linux-kernel - Re: [PATCH v3 1/2] PCI: imx6: Remove apps_reset toggle in _core

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Message-ID: <CAJ+vNU3mKiEE86SYFS0aEabkqRKADFDJN0giX73E0cA=GOyhjA@mail.gmail.com>
Date: Mon, 23 Jun 2025 10:33:13 -0700
From: Tim Harvey <tharvey@...eworks.com>
To: Manivannan Sadhasivam <mani@...nel.org>
Cc: Richard Zhu <hongxing.zhu@....com>, frank.li@....com, l.stach@...gutronix.de, 
	lpieralisi@...nel.org, kwilczynski@...nel.org, robh@...nel.org, 
	bhelgaas@...gle.com, shawnguo@...nel.org, s.hauer@...gutronix.de, 
	kernel@...gutronix.de, festevam@...il.com, linux-pci@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, imx@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] PCI: imx6: Remove apps_reset toggle in _core_reset functions

On Mon, Jun 23, 2025 at 4:42 AM Manivannan Sadhasivam <mani@...nel.org> wrote:
>
> On Mon, Jun 16, 2025 at 04:57:41PM +0800, Richard Zhu wrote:
> > apps_reset is LTSSM_EN on i.MX7, i.MX8MQ, i.MX8MM and i.MX8MP platforms.
> > Since the assertion/de-assertion of apps_reset(LTSSM_EN bit) had been
> > wrappered in imx_pcie_ltssm_enable() and imx_pcie_ltssm_disable();
> >
>
> What about other i.MX chipsets like 6Q and its cousins? Wouldn't this change
> affect them since they treat 'apps_reset' differently?
>
> - Mani

Hi Main,

This patch effectively brings back the behavior prior to commit
ef61c7d8d032 ("PCI: imx6: Deassert apps_reset in
imx_pcie_deassert_core_reset()") which caused the original
regressions.

To ease your concerns I've tested this patch on top of v6.16-rc3 with
the following IMX6 boards I have here with and without a PCI device
attached:
imx6q-gw51xx - no switch
imx6q-gw54xx - switch

I only have imx6qdl/imx8mm/imx8mp boards to test with.

>From what I can tell it doesn't look like the original patch that
added the 'symmetric' apps_reset de-assert was necessarily well
tested. It started out being added because as far as I can tell it
'looked' like the right thing to do [1]. You requested changes to the
commit log for wording [2],[3] but I'm unclear that anyone tested
this.

Best Regards,

Tim
[1] https://patchwork.kernel.org/project/linux-pci/patch/1727148464-14341-6-git-send-email-hongxing.zhu@nxp.com/
[2] https://patchwork.kernel.org/project/linux-pci/patch/1728981213-8771-6-git-send-email-hongxing.zhu@nxp.com/
[3] https://patchwork.kernel.org/project/linux-pci/patch/20241101070610.1267391-6-hongxing.zhu@nxp.com/