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@xxxxxx>
---
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@xxxxxx/
Changes since v1:
- Rebased patch on Linux 6.12-rc6
- Based on Krzysztof's feedback at:
https://lore.kernel.org/r/20241102141914.GA3440781@rocinante/
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
