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From: Marc Zyngier <maz@kernel.org>
To: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org
Cc: kernel-team@android.com, Alyssa Rosenzweig <alyssa@rosenzweig.io>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Bjorn Helgaas <bhelgaas@google.com>
Subject: [PATCH] PCI: apple: Reset the port for 100ms on probe
Date: Wed, 17 Nov 2021 16:00:53 +0000	[thread overview]
Message-ID: <20211117160053.232158-1-maz@kernel.org> (raw)

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


WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org
Cc: kernel-team@android.com, Alyssa Rosenzweig <alyssa@rosenzweig.io>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Bjorn Helgaas <bhelgaas@google.com>
Subject: [PATCH] PCI: apple: Reset the port for 100ms on probe
Date: Wed, 17 Nov 2021 16:00:53 +0000	[thread overview]
Message-ID: <20211117160053.232158-1-maz@kernel.org> (raw)

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


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             reply	other threads:[~2021-11-17 16:01 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-17 16:00 Marc Zyngier [this message]
2021-11-17 16:00 ` [PATCH] PCI: apple: Reset the port for 100ms on probe Marc Zyngier
2021-11-17 20:12 ` Bjorn Helgaas
2021-11-17 20:12   ` Bjorn Helgaas
2021-11-17 20:28   ` Pali Rohár
2021-11-17 20:28     ` Pali Rohár
2021-11-18 10:01     ` Marc Zyngier
2021-11-18 10:01       ` Marc Zyngier
2021-11-18 10:31       ` Pali Rohár
2021-11-18 10:31         ` Pali Rohár
2021-11-18 12:57         ` Marc Zyngier
2021-11-18 12:57           ` Marc Zyngier
2021-11-20 11:32           ` Pali Rohár
2021-11-20 11:32             ` Pali Rohár
2021-11-18 10:45       ` Marc Zyngier
2021-11-18 10:45         ` Marc Zyngier

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