On Tue, Oct 22, 2024 at 10:53:49AM -0500, Bjorn Helgaas wrote: > On Mon, Oct 21, 2024 at 02:49:13PM +0200, Stefan Eichenberger wrote: > > From: Stefan Eichenberger <stefan.eichenberger@xxxxxxxxxxx> > > > > The suspend/resume support is broken on the i.MX6QDL platform. This > > patch resets the link upon resuming to recover functionality. It shares > > most of the sequences with other i.MX devices but does not touch the > > critical registers, which might break PCIe. This patch addresses the > > same issue as the following downstream commit: > > https://github.com/nxp-imx/linux-imx/commit/4e92355e1f79d225ea842511fcfd42b343b32995 > > In comparison this patch will also reset the device if possible because > > the downstream patch alone would still make the ath10k driver crash. > > Without this patch suspend/resume will not work if a PCIe device is > > connected. The kernel will hang on resume and print an error: > > ath10k_pci 0000:01:00.0: Unable to change power state from D3hot to D0, device inaccessible > > 8<--- cut here --- > > Unhandled fault: imprecise external abort (0x1406) at 0x0106f944 > > https://chris.beams.io/posts/git-commit/ > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/maintainer-tip.rst?id=v6.11#n134 > > Add blank lines between paragraphs. Drop the "8<--- cut here" thing. Thanks for the feedback, I will fix this in the next version. > > What does "reset the link" mean? Please use the same terminology as > the PCIe spec when possible. I will try to come up with a better description in the next version. I think this sentence doesn't make sense anymore. > The downstream commit log ("WARNING: this is not the official > workaround; user should take own risk to use it") doesn't exactly > inspire confidence. > > It sounds like this resets *endpoints*? That sounds scary and > unexpected in suspend/resume. Yes, I completely agree with you, but NXP has never come up with an "official" workaround. Our problem is that with the current implementation, suspend/resume is completely broken when a PCIe device is connected. With this proposed patch we at least have a working device after resume. Even for the other i.MX devices, the driver resets the endpoints in the resume function (imx_pcie_resume_noir -> imx_pcie_host_init -> imx_pcie_assert_core_reset), we just do that now for the i.MX6QDL as well. If it is more appropriate to call imx_pcie_assert_core_reset in resume as we do for the other devices, that would be fine with me as well. I was thinking that if we need to reset the device anyway, we could put it into reset on suspend, as this might save some extra power. > > > Signed-off-by: Stefan Eichenberger <stefan.eichenberger@xxxxxxxxxxx> > > --- > > 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..09e3b15f0908a 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)) { > > + /** > > Single asterisks above, here, and below. Thanks, I will fix this in the next version. > > + * 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. > > s/msi/MSI/ Thanks, I will fix this in the next version. > > > + */ > > + 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, Regards, Stefan
