linux-kernel - [PATCH V2 2/2] PCI: designware-ep: Disable PTM capabilities for EP mode

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Message-ID: <20220926111017.12655-3-vidyas@nvidia.com>
Date:   Mon, 26 Sep 2022 16:40:17 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <jingoohan1@...il.com>, <gustavo.pimentel@...opsys.com>,
        <lpieralisi@...nel.org>, <robh@...nel.org>, <kw@...ux.com>,
        <bhelgaas@...gle.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kthota@...dia.com>, <mmaddireddy@...dia.com>, <vidyas@...dia.com>,
        <sagar.tv@...il.com>
Subject: [PATCH V2 2/2] PCI: designware-ep: Disable PTM capabilities for EP mode

Dual mode DesignWare PCIe IP has PTM capability enabled (if supported) even
in the EP mode. The PCIe compliance for the EP mode expects PTM
capabilities (ROOT_CAPABLE, RES_CAPABLE, CLK_GRAN) be disabled.
Hence disable PTM for the EP mode.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
Reviewed-by: Jingoo Han <jingoohan1@...il.com>
---
V2:
* Addressed review comment from Jingoo Han
* Added "Reviewed-by: Jingoo Han <jingoohan1@...il.com>"

 .../pci/controller/dwc/pcie-designware-ep.c    | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 095fb0291ec9..b88b6597194a 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -638,6 +638,7 @@ static int dw_pcie_ep_init_complete(struct dw_pcie_ep *ep)
 	struct dw_pcie_ep_func *ep_func;
 	struct device *dev = pci->dev;
 	struct pci_epc *epc = ep->epc;
+	unsigned int ptm_cap_base;
 	unsigned int offset;
 	unsigned int nbars;
 	u8 hdr_type;
@@ -690,6 +691,7 @@ static int dw_pcie_ep_init_complete(struct dw_pcie_ep *ep)
 	}
 
 	offset = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_REBAR);
+	ptm_cap_base = dw_pcie_ep_find_ext_capability(pci, PCI_EXT_CAP_ID_PTM);
 
 	dw_pcie_dbi_ro_wr_en(pci);
 
@@ -702,6 +704,22 @@ static int dw_pcie_ep_init_complete(struct dw_pcie_ep *ep)
 			dw_pcie_writel_dbi(pci, offset + PCI_REBAR_CAP, 0x0);
 	}
 
+	/*
+	 * PTM responder capability can be disabled only after disabling
+	 * PTM root capability.
+	 */
+	if (ptm_cap_base) {
+		dw_pcie_dbi_ro_wr_en(pci);
+		reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
+		reg &= ~PCI_PTM_CAP_ROOT;
+		dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
+
+		reg = dw_pcie_readl_dbi(pci, ptm_cap_base + PCI_PTM_CAP);
+		reg &= ~(PCI_PTM_CAP_RES | PCI_PTM_GRANULARITY_MASK);
+		dw_pcie_writel_dbi(pci, ptm_cap_base + PCI_PTM_CAP, reg);
+		dw_pcie_dbi_ro_wr_dis(pci);
+	}
+
 	dw_pcie_setup(pci);
 	dw_pcie_dbi_ro_wr_dis(pci);
 
-- 
2.17.1