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Subject[RFC PATCH 11/30] PCI: cadence: Add support to drive PERST# line using GPIO
Date
In platforms like TI's J721E EVM, the PERST# line is connected to a
GPIO line and PERST# should be driven high to indicate the clocks are
stable (As per Figure 2-10: Power Up of the PCIe CEM spec 3.0).

Add support to make GPIO drive PERST# line.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
---
drivers/pci/controller/pcie-cadence-host.c | 26 ++++++++++++++++++++++
1 file changed, 26 insertions(+)

diff --git a/drivers/pci/controller/pcie-cadence-host.c b/drivers/pci/controller/pcie-cadence-host.c
index 4ad8f2ece6e2..8b3b9827a8d6 100644
--- a/drivers/pci/controller/pcie-cadence-host.c
+++ b/drivers/pci/controller/pcie-cadence-host.c
@@ -3,6 +3,8 @@
// Cadence PCIe host controller driver.
// Author: Cyrille Pitchen <cyrille.pitchen@free-electrons.com>

+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
#include <linux/kernel.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
@@ -287,6 +289,7 @@ static int cdns_pcie_host_probe(struct platform_device *pdev)
struct pci_host_bridge *bridge;
struct list_head resources;
struct cdns_pcie_rc *rc;
+ struct gpio_desc *gpiod;
struct cdns_pcie *pcie;
struct resource *res;
int ret;
@@ -349,13 +352,36 @@ static int cdns_pcie_host_probe(struct platform_device *pdev)
dev_err(dev, "missing \"mem\"\n");
return -EINVAL;
}
+
pcie->mem_res = res;

+ gpiod = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
+ if (IS_ERR(gpiod)) {
+ ret = PTR_ERR(gpiod);
+ if (ret != -EPROBE_DEFER)
+ dev_err(dev, "Failed to get reset GPIO\n");
+ return ret;
+ }
+
ret = cdns_pcie_init_phy(dev, pcie);
if (ret) {
dev_err(dev, "failed to init phy\n");
return ret;
}
+
+ /*
+ * "Power Sequencing and Reset Signal Timings" table in
+ * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 3.0
+ * indicates PERST# should be deasserted after minimum of 100us
+ * once REFCLK is stable. The REFCLK to the connector in RC
+ * mode is selected while enabling the PHY. So deassert PERST#
+ * after 100 us.
+ */
+ if (gpiod) {
+ usleep_range(100, 200);
+ gpiod_set_value_cansleep(gpiod, 1);
+ }
+
platform_set_drvdata(pdev, pcie);

pm_runtime_enable(dev);
--
2.17.1
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