linux-kernel - [PATCH v2] PCI: dwc: Clean up some unnecessary codes in dw_pcie_suspend

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Message-Id: <20241115090321.527694-1-hongxing.zhu@nxp.com>
Date: Fri, 15 Nov 2024 17:03:21 +0800
From: Richard Zhu <hongxing.zhu@....com>
To: jingoohan1@...il.com,
	bhelgaas@...gle.com,
	lpieralisi@...nel.org,
	kw@...ux.com,
	manivannan.sadhasivam@...aro.org,
	robh@...nel.org,
	frank.li@....com
Cc: imx@...ts.linux.dev,
	kernel@...gutronix.de,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Richard Zhu <hongxing.zhu@....com>
Subject: [PATCH v2] PCI: dwc: Clean up some unnecessary codes in dw_pcie_suspend_noirq()

Before sending PME_TURN_OFF, don't test the LTSSM stat. Since it's safe
to send PME_TURN_OFF message regardless of whether the link is up or
down. So, there would be no need to test the LTSSM stat before sending
PME_TURN_OFF message.

Only dump the message when ltssm_stat is not in DETECT and POLL.
In the other words, there isn't a notification when no endpoint is
connected at all.

When the endpoint is connected and after PME_TURN_OFF is issued. Just
print out one information instead of an error and exit, if the link
doesn't entry DW_PCIE_LTSSM_L2_IDLE stat. Since the recovery would be
done in the following closely dw_pcie_resume_noirq().

Signed-off-by: Richard Zhu <hongxing.zhu@....com>
---
 .../pci/controller/dwc/pcie-designware-host.c | 37 ++++++++++---------
 drivers/pci/controller/dwc/pcie-designware.h  |  1 +
 2 files changed, 21 insertions(+), 17 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index f7ceeb785fb0..c2053555c44b 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -927,23 +927,26 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
 	if (dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKCTL) & PCI_EXP_LNKCTL_ASPM_L1)
 		return 0;
 
-	if (dw_pcie_get_ltssm(pci) > DW_PCIE_LTSSM_DETECT_ACT) {
-		/* Only send out PME_TURN_OFF when PCIE link is up */
-		if (pci->pp.ops->pme_turn_off)
-			pci->pp.ops->pme_turn_off(&pci->pp);
-		else
-			ret = dw_pcie_pme_turn_off(pci);
-
-		if (ret)
-			return ret;
+	if (pci->pp.ops->pme_turn_off)
+		pci->pp.ops->pme_turn_off(&pci->pp);
+	else
+		ret = dw_pcie_pme_turn_off(pci);
+	if (ret)
+		return ret;
 
-		ret = read_poll_timeout(dw_pcie_get_ltssm, val, val == DW_PCIE_LTSSM_L2_IDLE,
-					PCIE_PME_TO_L2_TIMEOUT_US/10,
-					PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
-		if (ret) {
-			dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
-			return ret;
-		}
+	ret = read_poll_timeout(dw_pcie_get_ltssm, val, val == DW_PCIE_LTSSM_L2_IDLE,
+				PCIE_PME_TO_L2_TIMEOUT_US/10,
+				PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
+	if (ret && (val > DW_PCIE_LTSSM_DETECT_WAIT))
+		/* Only dump message when ltssm_stat isn't in DETECT and POLL */
+		dev_info(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
+	else
+		/*
+		 * Refer to r6.0, sec 5.3.3.2.1, software should wait at least
+		 * 100ns after L2/L3 Ready before turning off refclock and
+		 * main power. It's harmless too when no endpoint connected.
+		 */
+		udelay(1);
 	}
 
 	dw_pcie_stop_link(pci);
@@ -952,7 +955,7 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
 
 	pci->suspended = true;
 
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(dw_pcie_suspend_noirq);
 
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 347ab74ac35a..bf036e66717e 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -330,6 +330,7 @@ enum dw_pcie_ltssm {
 	/* Need to align with PCIE_PORT_DEBUG0 bits 0:5 */
 	DW_PCIE_LTSSM_DETECT_QUIET = 0x0,
 	DW_PCIE_LTSSM_DETECT_ACT = 0x1,
+	DW_PCIE_LTSSM_DETECT_WAIT = 0x6,
 	DW_PCIE_LTSSM_L0 = 0x11,
 	DW_PCIE_LTSSM_L2_IDLE = 0x15,
 
-- 
2.37.1