From ee91cb570d9b12ae8cfcb96f7ea6fb80983b6a0a Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Tue, 23 Nov 2021 18:06:34 +0000 Subject: [PATCH] PCI: apple: Follow the PCIe specifications when resetting the port MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit While the Apple PCIe driver works correctly when directly booted from the firmware, it fails to initialise when the kernel is booted from a bootloader using PCIe such as u-boot. That's because we're missing a proper reset of the port (we only clear the reset, but never assert it). The PCIe spec requirements are two-fold: - PERST# must be asserted before setting up the clocks and stay asserted for at least 100us (Tperst-clk) - Once PERST# is deasserted, the OS must wait for at least 100ms "from the end of a Conventional Reset" before we can start talking to the devices Implementing this results in a booting system. [bhelgaas: #PERST -> PERST#, update spec references to current] Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up") Link: https://lore.kernel.org/r/20211123180636.80558-2-maz@kernel.org Signed-off-by: Marc Zyngier Signed-off-by: Bjorn Helgaas Reviewed-by: Luca Ceresoli Acked-by: Pali Rohár Cc: Alyssa Rosenzweig Cc: Lorenzo Pieralisi --- drivers/pci/controller/pcie-apple.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c index 1bf4d75b61be..c384777b0374 100644 --- a/drivers/pci/controller/pcie-apple.c +++ b/drivers/pci/controller/pcie-apple.c @@ -516,7 +516,7 @@ static int apple_pcie_setup_port(struct apple_pcie *pcie, int ret, i; reset = gpiod_get_from_of_node(np, "reset-gpios", 0, - GPIOD_OUT_LOW, "#PERST"); + GPIOD_OUT_LOW, "PERST#"); if (IS_ERR(reset)) return PTR_ERR(reset); @@ -539,13 +539,23 @@ static int apple_pcie_setup_port(struct apple_pcie *pcie, rmw_set(PORT_APPCLK_EN, port->base + PORT_APPCLK); + /* Assert PERST# before setting up the clock */ + gpiod_set_value(reset, 0); + ret = apple_pcie_setup_refclk(pcie, port); if (ret < 0) return ret; + /* The minimal Tperst-clk value is 100us (PCIe CEM r5.0, 2.9.2) */ + usleep_range(100, 200); + + /* Deassert PERST# */ rmw_set(PORT_PERST_OFF, port->base + PORT_PERST); gpiod_set_value(reset, 1); + /* Wait for 100ms after PERST# deassertion (PCIe r5.0, 6.6.1) */ + msleep(100); + ret = readl_relaxed_poll_timeout(port->base + PORT_STATUS, stat, stat & PORT_STATUS_READY, 100, 250000); if (ret < 0) {