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

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Message-ID:
 <AS8PR04MB867638BDCA5F47D478F597808C4EA@AS8PR04MB8676.eurprd04.prod.outlook.com>
Date: Tue, 8 Jul 2025 02:37:00 +0000
From: Hongxing Zhu <hongxing.zhu@....com>
To: "tharvey@...eworks.com" <tharvey@...eworks.com>, Manivannan Sadhasivam
	<mani@...nel.org>
CC: Frank Li <frank.li@....com>, "l.stach@...gutronix.de"
	<l.stach@...gutronix.de>, "lpieralisi@...nel.org" <lpieralisi@...nel.org>,
	"kwilczynski@...nel.org" <kwilczynski@...nel.org>, "robh@...nel.org"
	<robh@...nel.org>, "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"shawnguo@...nel.org" <shawnguo@...nel.org>, "s.hauer@...gutronix.de"
	<s.hauer@...gutronix.de>, "kernel@...gutronix.de" <kernel@...gutronix.de>,
	"festevam@...il.com" <festevam@...il.com>, "linux-pci@...r.kernel.org"
	<linux-pci@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "imx@...ts.linux.dev"
	<imx@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 1/2] PCI: imx6: Remove apps_reset toggle in _core_reset
 functions

> -----Original Message-----
> From: Tim Harvey <tharvey@...eworks.com>
> Sent: 2025年6月24日 1:33
> To: Manivannan Sadhasivam <mani@...nel.org>
> Cc: Hongxing Zhu <hongxing.zhu@....com>; Frank Li <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 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]
> 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
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> [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
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> [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
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