From: Hongxing Zhu <hongxing.zhu@nxp.com> To: Francesco Dolcini <francesco.dolcini@toradex.com> Cc: Lucas Stach <l.stach@pengutronix.de>, "bhelgaas@google.com" <bhelgaas@google.com>, "robh+dt@kernel.org" <robh+dt@kernel.org>, "broonie@kernel.org" <broonie@kernel.org>, "lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>, "jingoohan1@gmail.com" <jingoohan1@gmail.com>, "festevam@gmail.com" <festevam@gmail.com>, "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "kernel@pengutronix.de" <kernel@pengutronix.de>, dl-linux-imx <linux-imx@nxp.com> Subject: RE: [PATCH v9 6/8] PCI: imx6: Disable clocks and regulators after link is down Date: Thu, 9 Jun 2022 08:36:44 +0000 [thread overview] Message-ID: <AS8PR04MB86761E1C2D0C4CBE5E285BA88CA79@AS8PR04MB8676.eurprd04.prod.outlook.com> (raw) In-Reply-To: <20220609075305.GA20630@francesco-nb.int.toradex.com> > -----Original Message----- > From: Francesco Dolcini <francesco.dolcini@toradex.com> > Sent: 2022年6月9日 15:53 > To: Hongxing Zhu <hongxing.zhu@nxp.com> > Cc: Lucas Stach <l.stach@pengutronix.de>; bhelgaas@google.com; > robh+dt@kernel.org; broonie@kernel.org; lorenzo.pieralisi@arm.com; > jingoohan1@gmail.com; festevam@gmail.com; > francesco.dolcini@toradex.com; linux-pci@vger.kernel.org; > linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; > kernel@pengutronix.de; dl-linux-imx <linux-imx@nxp.com> > Subject: Re: [PATCH v9 6/8] PCI: imx6: Disable clocks and regulators after link is > down > > On Thu, Jun 09, 2022 at 06:17:46AM +0000, Hongxing Zhu wrote: > > > -----Original Message----- > > > From: Lucas Stach <l.stach@pengutronix.de> > > > Sent: 2022年6月8日 15:35 > > > To: Hongxing Zhu <hongxing.zhu@nxp.com>; bhelgaas@google.com; > > > robh+dt@kernel.org; broonie@kernel.org; lorenzo.pieralisi@arm.com; > > > jingoohan1@gmail.com; festevam@gmail.com; > > > francesco.dolcini@toradex.com > > > Cc: linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org; > > > linux-kernel@vger.kernel.org; kernel@pengutronix.de; dl-linux-imx > > > <linux-imx@nxp.com> > > > Subject: Re: [PATCH v9 6/8] PCI: imx6: Disable clocks and regulators > > > after link is down > > > > > > Am Freitag, dem 06.05.2022 um 09:47 +0800 schrieb Richard Zhu: > > > > Since i.MX PCIe doesn't support hot-plug, reduce power consumption > > > > as much as possible by disabling clocks and regulators and > > > > returning error when the link is down. > > > > > > > > Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com> > > > > --- > > > > drivers/pci/controller/dwc/pci-imx6.c | 19 +++++++++++++++---- > > > > 1 file changed, 15 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c > > > > b/drivers/pci/controller/dwc/pci-imx6.c > > > > index 3ce3993d5797..d122c12193a6 100644 > > > > --- a/drivers/pci/controller/dwc/pci-imx6.c > > > > +++ b/drivers/pci/controller/dwc/pci-imx6.c > > > > @@ -845,7 +845,9 @@ static int imx6_pcie_start_link(struct dw_pcie > *pci) > > > > /* Start LTSSM. */ > > > > imx6_pcie_ltssm_enable(dev); > > > > > > > > - dw_pcie_wait_for_link(pci); > > > > + ret = dw_pcie_wait_for_link(pci); > > > > + if (ret) > > > > + goto err_out; > > > > > > This adds back error handling that has been intentionally removed in > > > f81f095e8771 ("PCI: imx6: Allow to probe when dw_pcie_wait_for_link() > fails"). > > > While I agree that disabling the clocks and regulators is the right > > > thing to do when we don't manage to get a link, we should still > > > allow the driver to probe, so please add a "ret = 0" to this newly added > non-fatal error paths. > > > > > Thanks for your review comments. > > There would be a long latency if the link is down and probe is > > finished successfully. > > Since the dw_pcie_wait_for_link() would be invoked twice in every > > driver probe and resume operation later. Each dw_pcie_wait_for_link() > > would consume about > > 90,000*10 ~ 100,000*10 u-seconds. I'm afraid that such a long latency > > would bring bad user experience. > > > > Here are the logs when probe is allowed when PCIe link is down: > > [ 55.045954][ T1835] imx6q-pcie 5f000000.pcie: PM: calling > imx6_pcie_resume_noirq.742dfa074b40dca7ca925f0c49c905ec.cfi_jt+0x0/0x > 8 @ 1835, parent: bus@5f000000 > > ... > > [ 56.074566][ T1835] imx6q-pcie 5f000000.pcie: Phy link never came up > > [ 57.074816][ T1835] imx6q-pcie 5f000000.pcie: Phy link never came up > > ... > > [ 57.182300][ T1835] imx6q-pcie 5f000000.pcie: PM: > imx6_pcie_resume_noirq.742dfa074b40dca7ca925f0c49c905ec.cfi_jt+0x0/0x > 8 returned 0 after 2136334 usecs > > > > [ 57.182347][ T1835] imx6q-pcie 5f010000.pcie: PM: calling > imx6_pcie_resume_noirq.742dfa074b40dca7ca925f0c49c905ec.cfi_jt+0x0/0x > 8 @ 1835, parent: bus@5f000000 > > ... > > [ 58.210584][ T1835] imx6q-pcie 5f010000.pcie: Phy link never came up > > [ 59.210831][ T1835] imx6q-pcie 5f010000.pcie: Phy link never came up > > ... > > [ 59.318313][ T1835] imx6q-pcie 5f010000.pcie: PM: > imx6_pcie_resume_noirq.742dfa074b40dca7ca925f0c49c905ec.cfi_jt+0x0/0x > 8 returned 0 after 2135949 usecs > > > > So, I'm prefer that it's better to let the probe failed when link is down. > > How do you think about that? > > I think that recently Bjorn mentioned some concern with this approach, and I > agree with him. > I think that the probe of the PCIe root port should not fail if the link is down. > > What is the reason for such a long wait in dw_pcie_wait_for_link()? Is this > slowing down the resume process as a whole? Why called twice? (I'm not > familiar with that part of the code) > Thanks for your concerns. To avoid a corner link down issue, iMX PCIe driver force link up GEN1 speed firstly, then try to link up the highest speed later with one speed exchange. So, the dw_pcie_wait_for_link() would be invoked twice in iMX PCIe driver. Lucas and I try to figure out one method to avoid the long latency when resume back from suspend mode when link is down and probe is succeed. Best Regards Richard Zhu > Francesco
WARNING: multiple messages have this Message-ID (diff)
From: Hongxing Zhu <hongxing.zhu@nxp.com> To: Francesco Dolcini <francesco.dolcini@toradex.com> Cc: Lucas Stach <l.stach@pengutronix.de>, "bhelgaas@google.com" <bhelgaas@google.com>, "robh+dt@kernel.org" <robh+dt@kernel.org>, "broonie@kernel.org" <broonie@kernel.org>, "lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>, "jingoohan1@gmail.com" <jingoohan1@gmail.com>, "festevam@gmail.com" <festevam@gmail.com>, "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "kernel@pengutronix.de" <kernel@pengutronix.de>, dl-linux-imx <linux-imx@nxp.com> Subject: RE: [PATCH v9 6/8] PCI: imx6: Disable clocks and regulators after link is down Date: Thu, 9 Jun 2022 08:36:44 +0000 [thread overview] Message-ID: <AS8PR04MB86761E1C2D0C4CBE5E285BA88CA79@AS8PR04MB8676.eurprd04.prod.outlook.com> (raw) In-Reply-To: <20220609075305.GA20630@francesco-nb.int.toradex.com> > -----Original Message----- > From: Francesco Dolcini <francesco.dolcini@toradex.com> > Sent: 2022年6月9日 15:53 > To: Hongxing Zhu <hongxing.zhu@nxp.com> > Cc: Lucas Stach <l.stach@pengutronix.de>; bhelgaas@google.com; > robh+dt@kernel.org; broonie@kernel.org; lorenzo.pieralisi@arm.com; > jingoohan1@gmail.com; festevam@gmail.com; > francesco.dolcini@toradex.com; linux-pci@vger.kernel.org; > linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; > kernel@pengutronix.de; dl-linux-imx <linux-imx@nxp.com> > Subject: Re: [PATCH v9 6/8] PCI: imx6: Disable clocks and regulators after link is > down > > On Thu, Jun 09, 2022 at 06:17:46AM +0000, Hongxing Zhu wrote: > > > -----Original Message----- > > > From: Lucas Stach <l.stach@pengutronix.de> > > > Sent: 2022年6月8日 15:35 > > > To: Hongxing Zhu <hongxing.zhu@nxp.com>; bhelgaas@google.com; > > > robh+dt@kernel.org; broonie@kernel.org; lorenzo.pieralisi@arm.com; > > > jingoohan1@gmail.com; festevam@gmail.com; > > > francesco.dolcini@toradex.com > > > Cc: linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org; > > > linux-kernel@vger.kernel.org; kernel@pengutronix.de; dl-linux-imx > > > <linux-imx@nxp.com> > > > Subject: Re: [PATCH v9 6/8] PCI: imx6: Disable clocks and regulators > > > after link is down > > > > > > Am Freitag, dem 06.05.2022 um 09:47 +0800 schrieb Richard Zhu: > > > > Since i.MX PCIe doesn't support hot-plug, reduce power consumption > > > > as much as possible by disabling clocks and regulators and > > > > returning error when the link is down. > > > > > > > > Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com> > > > > --- > > > > drivers/pci/controller/dwc/pci-imx6.c | 19 +++++++++++++++---- > > > > 1 file changed, 15 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c > > > > b/drivers/pci/controller/dwc/pci-imx6.c > > > > index 3ce3993d5797..d122c12193a6 100644 > > > > --- a/drivers/pci/controller/dwc/pci-imx6.c > > > > +++ b/drivers/pci/controller/dwc/pci-imx6.c > > > > @@ -845,7 +845,9 @@ static int imx6_pcie_start_link(struct dw_pcie > *pci) > > > > /* Start LTSSM. */ > > > > imx6_pcie_ltssm_enable(dev); > > > > > > > > - dw_pcie_wait_for_link(pci); > > > > + ret = dw_pcie_wait_for_link(pci); > > > > + if (ret) > > > > + goto err_out; > > > > > > This adds back error handling that has been intentionally removed in > > > f81f095e8771 ("PCI: imx6: Allow to probe when dw_pcie_wait_for_link() > fails"). > > > While I agree that disabling the clocks and regulators is the right > > > thing to do when we don't manage to get a link, we should still > > > allow the driver to probe, so please add a "ret = 0" to this newly added > non-fatal error paths. > > > > > Thanks for your review comments. > > There would be a long latency if the link is down and probe is > > finished successfully. > > Since the dw_pcie_wait_for_link() would be invoked twice in every > > driver probe and resume operation later. Each dw_pcie_wait_for_link() > > would consume about > > 90,000*10 ~ 100,000*10 u-seconds. I'm afraid that such a long latency > > would bring bad user experience. > > > > Here are the logs when probe is allowed when PCIe link is down: > > [ 55.045954][ T1835] imx6q-pcie 5f000000.pcie: PM: calling > imx6_pcie_resume_noirq.742dfa074b40dca7ca925f0c49c905ec.cfi_jt+0x0/0x > 8 @ 1835, parent: bus@5f000000 > > ... > > [ 56.074566][ T1835] imx6q-pcie 5f000000.pcie: Phy link never came up > > [ 57.074816][ T1835] imx6q-pcie 5f000000.pcie: Phy link never came up > > ... > > [ 57.182300][ T1835] imx6q-pcie 5f000000.pcie: PM: > imx6_pcie_resume_noirq.742dfa074b40dca7ca925f0c49c905ec.cfi_jt+0x0/0x > 8 returned 0 after 2136334 usecs > > > > [ 57.182347][ T1835] imx6q-pcie 5f010000.pcie: PM: calling > imx6_pcie_resume_noirq.742dfa074b40dca7ca925f0c49c905ec.cfi_jt+0x0/0x > 8 @ 1835, parent: bus@5f000000 > > ... > > [ 58.210584][ T1835] imx6q-pcie 5f010000.pcie: Phy link never came up > > [ 59.210831][ T1835] imx6q-pcie 5f010000.pcie: Phy link never came up > > ... > > [ 59.318313][ T1835] imx6q-pcie 5f010000.pcie: PM: > imx6_pcie_resume_noirq.742dfa074b40dca7ca925f0c49c905ec.cfi_jt+0x0/0x > 8 returned 0 after 2135949 usecs > > > > So, I'm prefer that it's better to let the probe failed when link is down. > > How do you think about that? > > I think that recently Bjorn mentioned some concern with this approach, and I > agree with him. > I think that the probe of the PCIe root port should not fail if the link is down. > > What is the reason for such a long wait in dw_pcie_wait_for_link()? Is this > slowing down the resume process as a whole? Why called twice? (I'm not > familiar with that part of the code) > Thanks for your concerns. To avoid a corner link down issue, iMX PCIe driver force link up GEN1 speed firstly, then try to link up the highest speed later with one speed exchange. So, the dw_pcie_wait_for_link() would be invoked twice in iMX PCIe driver. Lucas and I try to figure out one method to avoid the long latency when resume back from suspend mode when link is down and probe is succeed. Best Regards Richard Zhu > Francesco _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-06-09 8:36 UTC|newest] Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-05-06 1:47 [PATCH v9 0/8] PCI: imx6: refine codes and add compliance tests mode support Richard Zhu 2022-05-06 1:47 ` Richard Zhu 2022-05-06 1:47 ` [PATCH v9 1/8] PCI: imx6: Encapsulate the clock enable into one standalone function Richard Zhu 2022-05-06 1:47 ` Richard Zhu 2022-06-08 18:51 ` Bjorn Helgaas 2022-06-08 18:51 ` Bjorn Helgaas 2022-06-09 6:18 ` Hongxing Zhu 2022-06-09 6:18 ` Hongxing Zhu 2022-05-06 1:47 ` [PATCH v9 2/8] PCI: imx6: Add the error propagation from host_init Richard Zhu 2022-05-06 1:47 ` Richard Zhu 2022-06-08 18:53 ` Bjorn Helgaas 2022-06-08 18:53 ` Bjorn Helgaas 2022-06-09 6:19 ` Hongxing Zhu 2022-06-09 6:19 ` Hongxing Zhu 2022-05-06 1:47 ` [PATCH v9 3/8] PCI: imx6: Move imx6_pcie_clk_disable() earlier Richard Zhu 2022-05-06 1:47 ` Richard Zhu 2022-06-08 7:14 ` Lucas Stach 2022-06-08 7:14 ` Lucas Stach 2022-05-06 1:47 ` [PATCH v9 4/8] PCI: imx6: Disable iMX6QDL PCIe REF clock when disable PCIe clocks Richard Zhu 2022-05-06 1:47 ` Richard Zhu 2022-06-08 7:18 ` Lucas Stach 2022-06-08 7:18 ` Lucas Stach 2022-05-06 1:47 ` [PATCH v9 5/8] PCI: imx6: Refine the regulator usage Richard Zhu 2022-05-06 1:47 ` Richard Zhu 2022-06-08 7:26 ` Lucas Stach 2022-06-08 7:26 ` Lucas Stach 2022-06-09 6:17 ` Hongxing Zhu 2022-06-09 6:17 ` Hongxing Zhu 2022-06-09 7:47 ` Lucas Stach 2022-06-09 7:47 ` Lucas Stach 2022-06-09 7:54 ` Hongxing Zhu 2022-06-09 7:54 ` Hongxing Zhu 2022-06-08 18:54 ` Bjorn Helgaas 2022-06-08 18:54 ` Bjorn Helgaas 2022-06-09 6:19 ` Hongxing Zhu 2022-06-09 6:19 ` Hongxing Zhu 2022-06-09 17:20 ` Bjorn Helgaas 2022-06-09 17:20 ` Bjorn Helgaas 2022-06-10 7:09 ` Hongxing Zhu 2022-06-10 7:09 ` Hongxing Zhu 2022-05-06 1:47 ` [PATCH v9 6/8] PCI: imx6: Disable clocks and regulators after link is down Richard Zhu 2022-05-06 1:47 ` Richard Zhu 2022-06-08 7:35 ` Lucas Stach 2022-06-08 7:35 ` Lucas Stach 2022-06-09 6:17 ` Hongxing Zhu 2022-06-09 6:17 ` Hongxing Zhu 2022-06-09 7:53 ` Francesco Dolcini 2022-06-09 7:53 ` Francesco Dolcini 2022-06-09 8:36 ` Hongxing Zhu [this message] 2022-06-09 8:36 ` Hongxing Zhu 2022-06-09 7:55 ` Lucas Stach 2022-06-09 7:55 ` Lucas Stach 2022-06-09 8:30 ` Hongxing Zhu 2022-06-09 8:30 ` Hongxing Zhu 2022-05-06 1:47 ` [PATCH v9 7/8] PCI: imx6: Move the phy driver callbacks to the proper places Richard Zhu 2022-05-06 1:47 ` Richard Zhu 2022-06-08 7:44 ` Lucas Stach 2022-06-08 7:44 ` Lucas Stach 2022-06-09 6:18 ` Hongxing Zhu 2022-06-09 6:18 ` Hongxing Zhu 2022-06-08 18:57 ` Bjorn Helgaas 2022-06-08 18:57 ` Bjorn Helgaas 2022-06-09 6:20 ` Hongxing Zhu 2022-06-09 6:20 ` Hongxing Zhu 2022-06-09 16:25 ` Bjorn Helgaas 2022-06-09 16:25 ` Bjorn Helgaas 2022-06-10 6:51 ` Hongxing Zhu 2022-06-10 6:51 ` Hongxing Zhu 2022-05-06 1:47 ` [PATCH v9 8/8] PCI: imx6: Add compliance tests mode support Richard Zhu 2022-05-06 1:47 ` Richard Zhu 2022-06-08 7:48 ` Lucas Stach 2022-06-08 7:48 ` Lucas Stach 2022-06-09 6:18 ` Hongxing Zhu 2022-06-09 6:18 ` Hongxing Zhu
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