[PATCH] PCI: apple: Reset the port for 100ms on probe

Marc Zyngier
2021-11-17T16:01:04Z

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 beacuse we're missing a proper reset of the port (we only
clear the reset, but never assert it).

Bring the port back to life by wiggling the #PERST pin for 100ms
(as per the spec).

Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up")
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
---
drivers/pci/controller/pcie-apple.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c
index 1bf4d75b61be..bbea5f6e0a68 100644
--- a/drivers/pci/controller/pcie-apple.c
+++ b/drivers/pci/controller/pcie-apple.c
@@ -543,6 +543,9 @@ static int apple_pcie_setup_port(struct apple_pcie *pcie,
if (ret < 0)
return ret;

+ /* Hold #PERST for 100ms as per the spec */
+ gpiod_set_value(reset, 0);
+ msleep(100);
rmw_set(PORT_PERST_OFF, port->base + PORT_PERST);
gpiod_set_value(reset, 1);

--
2.30.2