| Message ID | 20241022083147.2773123-1-s-vadapalli@ti.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | PCI: j721e: Deassert PERST# after a delay of PCIE_T_PVPERL_MS ms | expand |
Hello, > According to Section 2.2 of the PCI Express Card Electromechanical > Specification (Revision 5.1), in order to ensure that the power and the > reference clock are stable, PERST# has to be deasserted after a delay of > 100 milliseconds (TPVPERL). Currently, it is being assumed that the power > is already stable, which is not necessarily true. Hence, change the delay > to PCIE_T_PVPERL_MS to guarantee that power and reference clock are stable. [...] > This patch is based on commit > c2ee9f594da8 KVM: selftests: Fix build on on non-x86 architectures > of Mainline Linux. Why KVM? Do you have the link to this commit handy? [...] > if (pcie->reset_gpio) { > - fsleep(PCIE_T_PERST_CLK_US); > + msleep(PCIE_T_PVPERL_MS); fsleep() with the same macro and for the same reason is also used in the j721e_pcie_probe() callback. I think, we would want both changed. Krzysztof
On Sat, Nov 02, 2024 at 11:19:14PM +0900, Krzysztof Wilczyński wrote: > Hello, > > > According to Section 2.2 of the PCI Express Card Electromechanical > > Specification (Revision 5.1), in order to ensure that the power and the > > reference clock are stable, PERST# has to be deasserted after a delay of > > 100 milliseconds (TPVPERL). Currently, it is being assumed that the power > > is already stable, which is not necessarily true. Hence, change the delay > > to PCIE_T_PVPERL_MS to guarantee that power and reference clock are stable. > [...] > > This patch is based on commit > > c2ee9f594da8 KVM: selftests: Fix build on on non-x86 architectures > > of Mainline Linux. > > Why KVM? Do you have the link to this commit handy? Since this is a fix, I had based the patch on the latest Mainline Linux with the head corresponding to the aforementioned commit. Link: https://github.com/torvalds/linux/commit/c2ee9f594da8 > > [...] > > if (pcie->reset_gpio) { > > - fsleep(PCIE_T_PERST_CLK_US); > > + msleep(PCIE_T_PVPERL_MS); > > fsleep() with the same macro and for the same reason is also used in the > j721e_pcie_probe() callback. I think, we would want both changed. Thank you for pointing this out. I will update it in the v2 patch. Regards, Siddharth.
diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c index 284f2e0e4d26..e464cfc2c332 100644 --- a/drivers/pci/controller/cadence/pci-j721e.c +++ b/drivers/pci/controller/cadence/pci-j721e.c @@ -671,15 +671,14 @@ static int j721e_pcie_resume_noirq(struct device *dev) return ret; /* - * The "Power Sequencing and Reset Signal Timings" table of the - * PCI Express Card Electromechanical Specification, Revision - * 5.1, Section 2.9.2, Symbol "T_PERST-CLK", indicates PERST# - * should be deasserted after minimum of 100us once REFCLK is - * stable. The REFCLK to the connector in RC mode is selected - * while enabling the PHY. So deassert PERST# after 100 us. + * Section 2.2 of the PCI Express Card Electromechanical + * Specification (Revision 5.1) mandates that the deassertion + * of the PERST# signal should be delayed by 100 ms (TPVPERL). + * This shall ensure that the power and the reference clock + * are stable. */ if (pcie->reset_gpio) { - fsleep(PCIE_T_PERST_CLK_US); + msleep(PCIE_T_PVPERL_MS); gpiod_set_value_cansleep(pcie->reset_gpio, 1); }
According to Section 2.2 of the PCI Express Card Electromechanical Specification (Revision 5.1), in order to ensure that the power and the reference clock are stable, PERST# has to be deasserted after a delay of 100 milliseconds (TPVPERL). Currently, it is being assumed that the power is already stable, which is not necessarily true. Hence, change the delay to PCIE_T_PVPERL_MS to guarantee that power and reference clock are stable. Fixes: f96b69713733 ("PCI: j721e: Use T_PERST_CLK_US macro") Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com> --- Hello, This patch is based on commit c2ee9f594da8 KVM: selftests: Fix build on on non-x86 architectures of Mainline Linux. Regards, Siddharth. drivers/pci/controller/cadence/pci-j721e.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)