linux-kernel - [PATCH 4/8] PCI: iproc: Fix PCIe reset logic

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Date:	Tue, 15 Sep 2015 17:39:18 -0700
From:	Ray Jui <rjui@...adcom.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	Hauke Mehrtens <hauke@...ke-m.de>, <linux-pci@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<bcm-kernel-feedback-list@...adcom.com>,
	Ray Jui <rjui@...adcom.com>
Subject: [PATCH 4/8] PCI: iproc: Fix PCIe reset logic

The current iProc PCIe reset logic does not always properly reset the
device. For example, in the case when the perst_b signal is already
de-asserted in the bootloader, the current reset logic fails to trigger
a proper asssert -> de-assert reset sequence. This patch fixes the issue
by always triggering the proper reset sequence

This patch also explicitly selects the desired reset source, i.e.,
perst_b and reduces the wait time after the device comes out of reset
from 250 ms to 100 ms, based on recommendation from the ASIC team

Signed-off-by: Ray Jui <rjui@...adcom.com>
Reviewed-by: Vladimir Dreizin <vdreizin@...adcom.com>
Reviewed-by: Trac Hoang <trhoang@...adcom.com>
Reviewed-by: Scott Branden <sbranden@...adcom.com>
Tested-by: Vladimir Dreizin <vdreizin@...adcom.com>
Tested-by: Darren Edamura <dedamura@...adcom.com>
---
 drivers/pci/host/pcie-iproc.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/host/pcie-iproc.c b/drivers/pci/host/pcie-iproc.c
index 52e7ff2..80e0541 100644
--- a/drivers/pci/host/pcie-iproc.c
+++ b/drivers/pci/host/pcie-iproc.c
@@ -31,6 +31,8 @@
 #include "pcie-iproc.h"
 
 #define CLK_CONTROL_OFFSET           0x000
+#define EP_PERST_SOURCE_SELECT_SHIFT 2
+#define EP_PERST_SOURCE_SELECT       BIT(EP_PERST_SOURCE_SELECT_SHIFT)
 #define EP_MODE_SURVIVE_PERST_SHIFT  1
 #define EP_MODE_SURVIVE_PERST        BIT(EP_MODE_SURVIVE_PERST_SHIFT)
 #define RC_PCIE_RST_OUTPUT_SHIFT     0
@@ -119,15 +121,18 @@ static void iproc_pcie_reset(struct iproc_pcie *pcie)
 	u32 val;
 
 	/*
-	 * Configure the PCIe controller as root complex and send a downstream
-	 * reset
+	 * Select perst_b signal as reset source. Put the device into reset,
+	 * and then bring it out of reset
 	 */
-	val = EP_MODE_SURVIVE_PERST | RC_PCIE_RST_OUTPUT;
+	val = readl(pcie->base + CLK_CONTROL_OFFSET);
+	val &= ~EP_PERST_SOURCE_SELECT & ~EP_MODE_SURVIVE_PERST &
+		~RC_PCIE_RST_OUTPUT;
 	writel(val, pcie->base + CLK_CONTROL_OFFSET);
 	udelay(250);
-	val &= ~EP_MODE_SURVIVE_PERST;
+
+	val |= RC_PCIE_RST_OUTPUT;
 	writel(val, pcie->base + CLK_CONTROL_OFFSET);
-	msleep(250);
+	msleep(100);
 }
 
 static int iproc_pcie_check_link(struct iproc_pcie *pcie, struct pci_bus *bus)
-- 
1.9.1

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