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

[Manivannan Sadhasivam]

On Tue, Jul 08, 2025 at 02:37:00AM GMT, Hongxing Zhu wrote:
> > -----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.
> 

Okay, thanks for clarifying. Please include this information in the commit
message as well and also CC stable list for backporting since it fixes a bug.

- Mani

> 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]
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatch
> > work.kernel.org%2Fproject%2Flinux-pci%2Fpatch%2F1727148464-14341-6-gi
> > t-send-email-hongxing.zhu%40nxp.com%2F&data=05%7C02%7Chongxing.zhu
> > %40nxp.com%7Cdac60212c1c94cb24d7508ddb27c0f92%7C686ea1d3bc2b4c
> > 6fa92cd99c5c301635%7C0%7C0%7C638862968081967795%7CUnknown%7
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> > 7qGI92BfsbAERknsVjZO6cI527Enxgiiw%2FVatI7h4%3D&reserved=0
> > [2]
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatch
> > work.kernel.org%2Fproject%2Flinux-pci%2Fpatch%2F1728981213-8771-6-git
> > -send-email-hongxing.zhu%40nxp.com%2F&data=05%7C02%7Chongxing.zhu
> > %40nxp.com%7Cdac60212c1c94cb24d7508ddb27c0f92%7C686ea1d3bc2b4c
> > 6fa92cd99c5c301635%7C0%7C0%7C638862968081993466%7CUnknown%7
> > CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJ
> > XaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=lh
> > ER8F9ApfpgQcVCyMOBYho%2BXvlp79re4jX5C5gj1XY%3D&reserved=0
> > [3]
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatch
> > work.kernel.org%2Fproject%2Flinux-pci%2Fpatch%2F20241101070610.1267
> > 391-6-hongxing.zhu%40nxp.com%2F&data=05%7C02%7Chongxing.zhu%40nx
> > p.com%7Cdac60212c1c94cb24d7508ddb27c0f92%7C686ea1d3bc2b4c6fa92c
> > d99c5c301635%7C0%7C0%7C638862968082007982%7CUnknown%7CTWFp
> > bGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4z
> > MiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=kp4EqnV
> > lfUsVq4k9UV33LSpiwn%2F2OJlPzu2PApAttNs%3D&reserved=0

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