The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 64adde31c8e996a6db6f7a1a4131180e363aa9f2 Mon Sep 17 00:00:00 2001
From: Niklas Cassel niklas.cassel@linaro.org Date: Wed, 29 May 2019 11:43:52 +0200 Subject: [PATCH] PCI: qcom: Ensure that PERST is asserted for at least 100 ms
Currently, there is only a 1 ms sleep after asserting PERST.
Reading the datasheets for different endpoints, some require PERST to be asserted for 10 ms in order for the endpoint to perform a reset, others require it to be asserted for 50 ms.
Several SoCs using this driver uses PCIe Mini Card, where we don't know what endpoint will be plugged in.
The PCI Express Card Electromechanical Specification r2.0, section 2.2, "PERST# Signal" specifies:
"On power up, the deassertion of PERST# is delayed 100 ms (TPVPERL) from the power rails achieving specified operating limits."
Add a sleep of 100 ms before deasserting PERST, in order to ensure that we are compliant with the spec.
Fixes: 82a823833f4e ("PCI: qcom: Add Qualcomm PCIe controller driver") Signed-off-by: Niklas Cassel niklas.cassel@linaro.org Signed-off-by: Lorenzo Pieralisi lorenzo.pieralisi@arm.com Acked-by: Stanimir Varbanov svarbanov@mm-sol.com Cc: stable@vger.kernel.org # 4.5+
diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c index da5dd3639a49..7e581748ee9f 100644 --- a/drivers/pci/controller/dwc/pcie-qcom.c +++ b/drivers/pci/controller/dwc/pcie-qcom.c @@ -178,6 +178,8 @@ static void qcom_ep_reset_assert(struct qcom_pcie *pcie)
static void qcom_ep_reset_deassert(struct qcom_pcie *pcie) { + /* Ensure that PERST has been asserted for at least 100 ms */ + msleep(100); gpiod_set_value_cansleep(pcie->reset, 0); usleep_range(PERST_DELAY_US, PERST_DELAY_US + 500); }