From 127dbec39a5754346ca211460451b11412fe2cb3 Mon Sep 17 00:00:00 2001 From: Pali Rohár Date: Wed, 26 May 2021 17:59:34 +0200 Subject: arm: a37xx: pci: Don't put link into LTSSM Recovery state during probe MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit During our debugging of the Aardvark driver in Linux we have discovered that the PCIE_CORE_LINK_CTRL_STAT_REG register in fact controls standard PCIe Link Control Register for PCIe Root Bridge. This led us to discover that the name of the PCIE_CORE_LINK_TRAINING macro and the corresponding comment by this macro's usage is misleading; this bit in fact controls Retrain Link, which, according to PCIe base spec is defined as: A write of 1b to this bit initiates Link retraining by directing the Physical Layer LTSSM to the Recovery state. If the LTSSM is already in Recovery or Configuration, re-entering Recovery is permitted but not required. Entering Recovery state is normally done from LTSSM L0, L0s and L1 states. But since the pci-aardvark.c driver enables Link Training just a few lines above, the controller is not in L0 ready state yet. So setting aardvark bit PCIE_CORE_LINK_TRAINING does not actually enter Recovery state at this place. Moreover, trying to enter LTSSM Recovery state without other configuration is causing issues for some cards (e.g. Atheros AR9xxx and QCA9xxx). Since Recovery state is not entered, these issues are not triggered. Remove code which tries to enter LTSSM Recovery state completely. Signed-off-by: Pali Rohár Reviewed-by: Marek Behún Reviewed-by: Stefan Roese --- drivers/pci/pci-aardvark.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/drivers/pci/pci-aardvark.c b/drivers/pci/pci-aardvark.c index c43d4f309b..06c567e236 100644 --- a/drivers/pci/pci-aardvark.c +++ b/drivers/pci/pci-aardvark.c @@ -613,11 +613,6 @@ static int pcie_advk_setup_hw(struct pcie_advk *pcie) reg |= PIO_CTRL_ADDR_WIN_DISABLE; advk_writel(pcie, reg, PIO_CTRL); - /* Start link training */ - reg = advk_readl(pcie, PCIE_CORE_LINK_CTRL_STAT_REG); - reg |= PCIE_CORE_LINK_TRAINING; - advk_writel(pcie, reg, PCIE_CORE_LINK_CTRL_STAT_REG); - /* Wait for PCIe link up */ if (pcie_advk_wait_for_link(pcie)) return -ENXIO; -- cgit