PCI: iproc: Add 500ms delay during device shutdown

During soft reset (e.g., "reboot" from Linux) on some iProc-based SOCs, the
LCPLL clock and PERST both go off simultaneously.  This seems in accordance
with the PCIe Card Electromechanical spec, r2.0, sec 2.2.3, which says the
clock goes inactive after PERST# goes active, but doesn't specify how long
the clock should be valid after PERST#.

However, we have observed that with the iProc Stingray, some Intel NVMe
endpoints, e.g., the P3700 400GB series, are not detected correctly upon
the next boot sequence unless the clock remains valid for some time after
PERST# is asserted.

Delay 500ms after asserting PERST# before performing a reboot.  The 500ms
is experimentally determined.

Signed-off-by: Oza Pawandeep <oza.oza@broadcom.com>
[bhelgaas: changelog, add spec reference, fold in iproc_pcie_shutdown()
export from Arnd Bergmann <arnd@arndb.de>]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>

1 files changed, 24 insertions, 15 deletions

diff --git a/drivers/pci/host/pcie-iproc.c b/drivers/pci/host/pcie-iproc.c
index 9a006cbc3021..fe2e5aaaff55 100644
--- a/drivers/pci/host/pcie-iproc.c
+++ b/drivers/pci/host/pcie-iproc.c
@@ -671,7 +671,7 @@ static struct pci_ops iproc_pcie_ops = {
 	.write = iproc_pcie_config_write32,
 };
 
-static void iproc_pcie_reset(struct iproc_pcie *pcie)
+static void iproc_pcie_perst_ctrl(struct iproc_pcie *pcie, bool assert)
 {
 	u32 val;
 
@@ -683,20 +683,28 @@ static void iproc_pcie_reset(struct iproc_pcie *pcie)
 	if (pcie->ep_is_internal)
 		return;
 
-	/*
-	 * Select perst_b signal as reset source. Put the device into reset,
-	 * and then bring it out of reset
-	 */
-	val = iproc_pcie_read_reg(pcie, IPROC_PCIE_CLK_CTRL);
-	val &= ~EP_PERST_SOURCE_SELECT & ~EP_MODE_SURVIVE_PERST &
-		~RC_PCIE_RST_OUTPUT;
-	iproc_pcie_write_reg(pcie, IPROC_PCIE_CLK_CTRL, val);
-	udelay(250);
-
-	val |= RC_PCIE_RST_OUTPUT;
-	iproc_pcie_write_reg(pcie, IPROC_PCIE_CLK_CTRL, val);
-	msleep(100);
+	if (assert) {
+		val = iproc_pcie_read_reg(pcie, IPROC_PCIE_CLK_CTRL);
+		val &= ~EP_PERST_SOURCE_SELECT & ~EP_MODE_SURVIVE_PERST &
+			~RC_PCIE_RST_OUTPUT;
+		iproc_pcie_write_reg(pcie, IPROC_PCIE_CLK_CTRL, val);
+		udelay(250);
+	} else {
+		val = iproc_pcie_read_reg(pcie, IPROC_PCIE_CLK_CTRL);
+		val |= RC_PCIE_RST_OUTPUT;
+		iproc_pcie_write_reg(pcie, IPROC_PCIE_CLK_CTRL, val);
+		msleep(100);
+	}
+}
+
+int iproc_pcie_shutdown(struct iproc_pcie *pcie)
+{
+	iproc_pcie_perst_ctrl(pcie, true);
+	msleep(500);
+
+	return 0;
 }
+EXPORT_SYMBOL_GPL(iproc_pcie_shutdown);
 
 static int iproc_pcie_check_link(struct iproc_pcie *pcie)
 {
@@ -1379,7 +1387,8 @@ int iproc_pcie_setup(struct iproc_pcie *pcie, struct list_head *res)
 		goto err_exit_phy;
 	}
 
-	iproc_pcie_reset(pcie);
+	iproc_pcie_perst_ctrl(pcie, true);
+	iproc_pcie_perst_ctrl(pcie, false);
 
 	if (pcie->need_ob_cfg) {
 		ret = iproc_pcie_map_ranges(pcie, res);