[PATCH v2] PCI: j721e: Deassert PERST# after a delay of PCIE_T_PVPERL_MS ms
From: Siddharth Vadapalli <s-vadapalli@ti.com>
Date: 2024-11-04 07:44:58
Also in:
linux-omap, linux-pci, lkml
Subsystem:
pci driver for cadence pcie ip, pci driver for ti dra7xx/j721e, pci native host bridge and endpoint drivers, pci subsystem, the rest · Maintainers:
Vignesh Raghavendra, Lorenzo Pieralisi, Krzysztof Wilczyński, Manivannan Sadhasivam, Bjorn Helgaas, Linus Torvalds
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: f3e25911a430 ("PCI: j721e: Add TI J721E PCIe driver")
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
59b723cd2adb Linux 6.12-rc6
of Mainline Linux.
v1:
https://lore.kernel.org/r/20241022083147.2773123-1-s-vadapalli@ti.com/ (local)
Changes since v1:
- Rebased patch on Linux 6.12-rc6
- Based on Krzysztof's feedback at:
https://lore.kernel.org/r/20241102141914.GA3440781@rocinante/ (local)
PCIE_T_PERST_CLK_US has been replaced with PCIE_T_PVPERL_MS in
j721e_pcie_probe() as well.
- Added Fixes tag corresponding to the above change in the commit
message.
Regards,
Siddharth.
drivers/pci/controller/cadence/pci-j721e.c | 26 ++++++++++------------
1 file changed, 12 insertions(+), 14 deletions(-)
diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
index 284f2e0e4d26..e091c3e55b5c 100644
--- a/drivers/pci/controller/cadence/pci-j721e.c
+++ b/drivers/pci/controller/cadence/pci-j721e.c@@ -572,15 +572,14 @@ static int j721e_pcie_probe(struct platform_device *pdev) pcie->refclk = clk; /* - * 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 (gpiod) { - fsleep(PCIE_T_PERST_CLK_US); + msleep(PCIE_T_PVPERL_MS); gpiod_set_value_cansleep(gpiod, 1); }
@@ -671,15 +670,14 @@ 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); }
--
2.40.1