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Message-ID:
<AS8PR04MB867619F514B354197802B8918C512@AS8PR04MB8676.eurprd04.prod.outlook.com>
Date: Mon, 4 Nov 2024 01:31:17 +0000
From: Hongxing Zhu <hongxing.zhu@....com>
To: Bjorn Helgaas <helgaas@...nel.org>, Stefan Eichenberger
<eichest@...il.com>, Lucas Stach <l.stach@...gutronix.de>
CC: "lpieralisi@...nel.org" <lpieralisi@...nel.org>, "kw@...ux.com"
<kw@...ux.com>, "manivannan.sadhasivam@...aro.org"
<manivannan.sadhasivam@...aro.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>, Francesco Dolcini <francesco.dolcini@...adex.com>,
Frank Li <frank.li@....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>, Stefan Eichenberger
<stefan.eichenberger@...adex.com>
Subject: RE: [PATCH v4] PCI: imx6: Add suspend/resume support for i.MX6QDL
> -----Original Message-----
> From: Bjorn Helgaas <helgaas@...nel.org>
> Sent: 2024年11月2日 3:34
> To: Stefan Eichenberger <eichest@...il.com>; Hongxing Zhu
> <hongxing.zhu@....com>; Lucas Stach <l.stach@...gutronix.de>
> Cc: lpieralisi@...nel.org; kw@...ux.com; manivannan.sadhasivam@...aro.org;
> robh@...nel.org; bhelgaas@...gle.com; shawnguo@...nel.org;
> s.hauer@...gutronix.de; kernel@...gutronix.de; festevam@...il.com;
> Francesco Dolcini <francesco.dolcini@...adex.com>; Frank Li
> <frank.li@....com>; linux-pci@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org; imx@...ts.linux.dev;
> linux-kernel@...r.kernel.org; Stefan Eichenberger
> <stefan.eichenberger@...adex.com>
> Subject: Re: [PATCH v4] PCI: imx6: Add suspend/resume support for i.MX6QDL
>
> On Wed, Oct 30, 2024 at 11:32:45AM +0100, Stefan Eichenberger wrote:
> > From: Stefan Eichenberger <stefan.eichenberger@...adex.com>
> >
> > The suspend/resume functionality is currently broken on the i.MX6QDL
> > platform, as documented in the NXP errata (ERR005723):
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.
> >
> nxp.com%2Fdocs%2Fen%2Ferrata%2FIMX6DQCE.pdf&data=05%7C02%7Chong
> xing.zh
> >
> u%40nxp.com%7C9039460e3cf54773efcd08dcfaac2bc7%7C686ea1d3bc2b4c6f
> a92cd
> >
> 99c5c301635%7C0%7C0%7C638660864604098652%7CUnknown%7CTWFpbGZs
> b3d8eyJWI
> >
> joiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%
> 7C%7
> >
> C%7C&sdata=WACKwvUPlTZJcxjkLe7YI3ZnITtxEj6wULhMndh8zNE%3D&reserv
> ed=0
> >
> > This patch addresses the issue by sharing most of the suspend/resume
> > sequences used by other i.MX devices, while avoiding modifications to
> > critical registers that disrupt the PCIe functionality. It targets the
> > same problem as the following downstream commit:
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith
> >
> ub.com%2Fnxp-imx%2Flinux-imx%2Fcommit%2F4e92355e1f79d225ea842511fc
> fd42
> >
> b343b32995&data=05%7C02%7Chongxing.zhu%40nxp.com%7C9039460e3cf54
> 773efc
> >
> d08dcfaac2bc7%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63866
> 086460
> >
> 4121904%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2lu
> MzIiLC
> >
> JBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=tafoT8ug4EehGXrE
> NzQOb%
> > 2F7rD%2Fra8%2BefnAEiV%2FB8Afc%3D&reserved=0
> >
> > Unlike the downstream commit, this patch also resets the connected
> > PCIe device if possible. Without this reset, certain drivers, such as
> > ath10k or iwlwifi, will crash on resume. The device reset is also done
> > by the driver on other i.MX platforms, making this patch consistent
> > with existing practices.
> >
> > Without this patch, suspend/resume will fail on i.MX6QDL devices if a
> > PCIe device is connected. Upon resuming, the kernel will hang and
> > display an error. Here's an example of the error encountered with the
> > ath10k driver:
> > ath10k_pci 0000:01:00.0: Unable to change power state from D3hot to
> > D0, device inaccessible Unhandled fault: imprecise external abort
> > (0x1406) at 0x0106f944
> >
> > Signed-off-by: Stefan Eichenberger <stefan.eichenberger@...adex.com>
>
> Richard and Lucas, does this look OK to you? Since you're listed as maintainers
> of pci-imx6.c, I'd like to have your ack before merging this.
>
Sorry to reply late.
I'm fine with that.
Thanks.
Acked-by: Richard Zhu <hongxing.zhu@....com>
Best Regards
Richard Zhu
> > ---
> > Changes in v4:
> > - Improve commit message (Bjorn)
> > - Fix style issue on comments (Bjorn)
> > - s/msi/MSI (Bjorn)
> >
> > Changes in v3:
> > - Added a new flag to the driver data to indicate that the suspend/resume
> > is broken on the i.MX6QDL platform. (Frank)
> > - Fix comments to be more relevant (Mani)
> > - Use imx_pcie_assert_core_reset in suspend (Mani)
> >
> > drivers/pci/controller/dwc/pci-imx6.c | 57
> > +++++++++++++++++++++------
> > 1 file changed, 46 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > b/drivers/pci/controller/dwc/pci-imx6.c
> > index 808d1f1054173..c8d5c90aa4d45 100644
> > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > @@ -82,6 +82,11 @@ enum imx_pcie_variants {
> > #define IMX_PCIE_FLAG_HAS_SERDES BIT(6)
> > #define IMX_PCIE_FLAG_SUPPORT_64BIT BIT(7)
> > #define IMX_PCIE_FLAG_CPU_ADDR_FIXUP BIT(8)
> > +/*
> > + * Because of ERR005723 (PCIe does not support L2 power down) we need
> > +to
> > + * workaround suspend resume on some devices which are affected by this
> errata.
> > + */
> > +#define IMX_PCIE_FLAG_BROKEN_SUSPEND BIT(9)
> >
> > #define imx_check_flag(pci, val) (pci->drvdata->flags & val)
> >
> > @@ -1237,9 +1242,19 @@ static int imx_pcie_suspend_noirq(struct device
> *dev)
> > return 0;
> >
> > imx_pcie_msi_save_restore(imx_pcie, true);
> > - imx_pcie_pm_turnoff(imx_pcie);
> > - imx_pcie_stop_link(imx_pcie->pci);
> > - imx_pcie_host_exit(pp);
> > + if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_BROKEN_SUSPEND)) {
> > + /*
> > + * The minimum for a workaround would be to set PERST# and to
> > + * set the PCIE_TEST_PD flag. However, we can also disable the
> > + * clock which saves some power.
> > + */
> > + imx_pcie_assert_core_reset(imx_pcie);
> > + imx_pcie->drvdata->enable_ref_clk(imx_pcie, false);
> > + } else {
> > + imx_pcie_pm_turnoff(imx_pcie);
> > + imx_pcie_stop_link(imx_pcie->pci);
> > + imx_pcie_host_exit(pp);
> > + }
> >
> > return 0;
> > }
> > @@ -1253,14 +1268,32 @@ static int imx_pcie_resume_noirq(struct device
> *dev)
> > if (!(imx_pcie->drvdata->flags & IMX_PCIE_FLAG_SUPPORTS_SUSPEND))
> > return 0;
> >
> > - ret = imx_pcie_host_init(pp);
> > - if (ret)
> > - return ret;
> > - imx_pcie_msi_save_restore(imx_pcie, false);
> > - dw_pcie_setup_rc(pp);
> > + if (imx_check_flag(imx_pcie, IMX_PCIE_FLAG_BROKEN_SUSPEND)) {
> > + ret = imx_pcie->drvdata->enable_ref_clk(imx_pcie, true);
> > + if (ret)
> > + return ret;
> > + ret = imx_pcie_deassert_core_reset(imx_pcie);
> > + if (ret)
> > + return ret;
> > + /*
> > + * Using PCIE_TEST_PD seems to disable MSI and powers down the
> > + * root complex. This is why we have to setup the rc again and
> > + * why we have to restore the MSI register.
> > + */
> > + ret = dw_pcie_setup_rc(&imx_pcie->pci->pp);
> > + if (ret)
> > + return ret;
> > + imx_pcie_msi_save_restore(imx_pcie, false);
> > + } else {
> > + ret = imx_pcie_host_init(pp);
> > + if (ret)
> > + return ret;
> > + imx_pcie_msi_save_restore(imx_pcie, false);
> > + dw_pcie_setup_rc(pp);
> >
> > - if (imx_pcie->link_is_up)
> > - imx_pcie_start_link(imx_pcie->pci);
> > + if (imx_pcie->link_is_up)
> > + imx_pcie_start_link(imx_pcie->pci);
> > + }
> >
> > return 0;
> > }
> > @@ -1485,7 +1518,9 @@ static const struct imx_pcie_drvdata drvdata[] = {
> > [IMX6Q] = {
> > .variant = IMX6Q,
> > .flags = IMX_PCIE_FLAG_IMX_PHY |
> > - IMX_PCIE_FLAG_IMX_SPEED_CHANGE,
> > + IMX_PCIE_FLAG_IMX_SPEED_CHANGE |
> > + IMX_PCIE_FLAG_BROKEN_SUSPEND |
> > + IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
> > .dbi_length = 0x200,
> > .gpr = "fsl,imx6q-iomuxc-gpr",
> > .clk_names = imx6q_clks,
> > --
> > 2.43.0
> >
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