Re: [PATCH] PCI: apple: Reset the port for 100ms on probe
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2021-11-17 20:12:48
Also in:
linux-pci, lkml
[+cc Pali] On Wed, Nov 17, 2021 at 04:00:53PM +0000, Marc Zyngier wrote:
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).
s/beacuse/because/
Bring the port back to life by wiggling the #PERST pin for 100ms (as per the spec).
I cc'd Pali because I think he's interested in consolidating or somehow rationalizing delays like this. If we have a specific spec reference here, I think it would help that effort. I *think* it's PCIe r5.0, sec 6.6.1, which mentions the 100ms along with some additional constraints, like waiting 100ms after Link training completes for ports that support > 5.0 GT/s, whether Readiness Notifications are used, and CRS Software Visiblity.
quoted hunk ↗ jump to hunk
Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up") Signed-off-by: Marc Zyngier <maz@kernel.org> Cc: Alyssa Rosenzweig <redacted> Cc: Lorenzo Pieralisi <redacted> 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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