linux-kernel - [PATCH v2 2/3] PCI: qcom: Read back PARF

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Message-Id: <20240210-topic-8280_pcie-v2-2-1cef4b606883@linaro.org>
Date: Sat, 10 Feb 2024 18:10:06 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Bjorn Andersson <andersson@...nel.org>, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.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>
Cc: linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Johan Hovold <johan+linaro@...nel.org>, 
 Konrad Dybcio <konrad.dybcio@...aro.org>
Subject: [PATCH v2 2/3] 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".

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
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 cbde9effa352..6a469ed213ce 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -539,6 +539,7 @@ 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)

-- 
2.40.1