linux-kernel - [PATCH 3/4] PCI: qcom: Read back PARF

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Date: Wed, 27 Dec 2023 23:17:21 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Manivannan Sadhasivam <mani@...nel.org>, 
 Bjorn Andersson <andersson@...nel.org>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Krzysztof Wilczyński <kw@...ux.com>, 
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
 Philipp Zabel <p.zabel@...gutronix.de>, 
 Stanimir Varbanov <svarbanov@...sol.com>, 
 Andrew Murray <amurray@...goodpenguin.co.uk>, Vinod Koul <vkoul@...nel.org>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>, 
 linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Konrad Dybcio <konrad.dybcio@...aro.org>
Subject: [PATCH 3/4] PCI: qcom: Read back PARF_LTSSM register

To ensure write completion, read the PARF_LTSSM register after setting
the LTSSM enable bit before polling for "link up".

Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index a02dc197c495..3d77269e70da 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -540,6 +540,7 @@ static void qcom_pcie_2_3_2_ltssm_enable(struct qcom_pcie *pcie)
 	val = readl(pcie->parf + PARF_LTSSM);
 	val |= LTSSM_EN;
 	writel(val, pcie->parf + PARF_LTSSM);
+	readl(pcie->parf + PARF_LTSSM);
 }
 
 static int qcom_pcie_get_resources_2_3_2(struct qcom_pcie *pcie)

-- 
2.43.0