[PATCH v2 1/3] PCI/PM: Observe reset delay irrespective of bridge_d3

From: Lukas Wunner <lukas@wunner.de>
To: Bjorn Helgaas <helgaas@kernel.org>, linux-pci@vger.kernel.org
Cc: Keith Busch <kbusch@kernel.org>, Ashok Raj <ashok.raj@intel.com>,
	Sathyanarayanan Kuppuswamy 
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	Ravi Kishore Koppuravuri <ravi.kishore.koppuravuri@intel.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Sheng Bi <windy.bi.enflame@gmail.com>,
	Stanislav Spassov <stanspas@amazon.de>,
	Yang Su <yang.su@linux.alibaba.com>
Subject: [PATCH v2 1/3] PCI/PM: Observe reset delay irrespective of bridge_d3
Date: Sun, 15 Jan 2023 09:20:31 +0100	[thread overview]
Message-ID: <eb37fa345285ec8bacabbf06b020b803f77bdd3d.1673769517.git.lukas@wunner.de> (raw)
In-Reply-To: <cover.1673769517.git.lukas@wunner.de>

If a PCI bridge is suspended to D3cold upon entering system sleep,
resuming it entails a Fundamental Reset per PCIe r6.0 sec 5.8.

The delay prescribed after a Fundamental Reset in PCIe r6.0 sec 6.6.1
is sought to be observed by:

  pci_pm_resume_noirq()
    pci_pm_bridge_power_up_actions()
      pci_bridge_wait_for_secondary_bus()

However, pci_bridge_wait_for_secondary_bus() bails out if the bridge_d3
flag is not set.  That flag indicates whether a bridge is allowed to
suspend to D3cold at *runtime*.

Hence *no* delay is observed on resume from system sleep if runtime
D3cold is forbidden.  That doesn't make any sense, so drop the bridge_d3
check from pci_bridge_wait_for_secondary_bus().

The purpose of the bridge_d3 check was probably to avoid delays if a
bridge remained in D0 during suspend.  However the sole caller of
pci_bridge_wait_for_secondary_bus(), pci_pm_bridge_power_up_actions(),
is only invoked if the previous power state was D3cold.  Hence the
additional bridge_d3 check seems superfluous.

Fixes: ad9001f2f411 ("PCI/PM: Add missing link delays required by the PCIe spec")
Tested-by: Ravi Kishore Koppuravuri <ravi.kishore.koppuravuri@intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: stable@vger.kernel.org # v5.5+
---
Changes v1 -> v2:
 * Add Reviewed-by tags (Mika, Sathyanarayanan)

 drivers/pci/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index fba95486caaf..f43f3e84f634 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4964,7 +4964,7 @@ void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev)
 	if (pci_dev_is_disconnected(dev))
 		return;
 
-	if (!pci_is_bridge(dev) || !dev->bridge_d3)
+	if (!pci_is_bridge(dev))
 		return;
 
 	down_read(&pci_bus_sem);
-- 
2.39.0

