[v4] PCI: dwc: Clean up some unnecessary codes in dw_pcie_suspend_noirq()

Commit Message

Richard Zhu Nov. 19, 2024, 6:21 a.m. UTC

Before sending PME_TURN_OFF, don't test the LTSSM state. 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 state before sending
PME_TURN_OFF message.

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

Signed-off-by: Richard Zhu <[e-mail]>
---
v4 changes:
- Keep error return when L2 entry is failed and the endpoint is
  connected refer to Krishna' comments. Thanks.
v3 changes:
- Refine the commit message refer to Manivannan's comments.
- Regarding Frank's comments, avoid 10ms wait when no link up.
v2 changes:
- Don't remove L2 poll check.
- Add one 1us delay after L2 entry.
- No error return when L2 entry is timeout
- Don't print message when no link up.
---
 .../pci/controller/dwc/pcie-designware-host.c | 38 +++++++++++--------
 drivers/pci/controller/dwc/pcie-designware.h  |  1 +
 2 files changed, 23 insertions(+), 16 deletions(-)

Patch

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 24e89b66b772..d36e01539ce7 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -927,25 +927,31 @@  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;
 
-	/* Only send out PME_TURN_OFF when PCIE link is up */
-	if (dw_pcie_get_ltssm(pci) > DW_PCIE_LTSSM_DETECT_ACT) {
-		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 ||
+				val <= DW_PCIE_LTSSM_DETECT_WAIT,
+				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_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
+		return ret;
 	}
 
+	/*
+	 * 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);
 	if (pci->pp.ops->deinit)
 		pci->pp.ops->deinit(&pci->pp);
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,