[PATCH v3 1/2] PCI: imx6: Remove apps_reset toggle in _core_reset functions

[Hongxing Zhu]

> -----Original Message-----
> From: Tim Harvey <tharvey at gateworks.com>
> Sent: 2025年6月24日 1:33
> To: Manivannan Sadhasivam <mani at kernel.org>
> Cc: Hongxing Zhu <hongxing.zhu at nxp.com>; Frank Li <frank.li at nxp.com>;
> l.stach at pengutronix.de; lpieralisi at kernel.org; kwilczynski at kernel.org;
> robh at kernel.org; bhelgaas at google.com; shawnguo at kernel.org;
> s.hauer at pengutronix.de; kernel at pengutronix.de; festevam at gmail.com;
> linux-pci at vger.kernel.org; linux-arm-kernel at lists.infradead.org;
> imx at lists.linux.dev; linux-kernel at vger.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 at kernel.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 Mani:
Sorry to reply late.
Only i.MX7D, i.MX8MQ, i.MX8MM, and i.MX8MP have the apps_reset. No problems
are found with this change in my local tests on these four platforms.
With this change, the assertion/deassertion of ltssm_en bit are unified into
 imx_pcie_ltssm_enable() and imx_pcie_ltssm_disable() functions, aligned with
other i.MX platforms.

Best Regards
Richard Zhu
> 
> 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.
>
Hi Tim: 
Thanks for your explains and tests.

Best Regards
Richard Zhu

> Best Regards,
> 
> Tim
> [1]
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> [3]
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