linux-kernel - [PATCH V6 12/16] PCI: tegra194: Enable support for 256 Byte payload

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Date:   Thu, 21 Jul 2022 19:50:48 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <bhelgaas@...gle.com>, <lpieralisi@...nel.org>,
        <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <jingoohan1@...il.com>, <gustavo.pimentel@...opsys.com>
CC:     <kw@...ux.com>, <kishon@...com>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <kthota@...dia.com>,
        <mmaddireddy@...dia.com>, <vidyas@...dia.com>, <sagar.tv@...il.com>
Subject: [PATCH V6 12/16] PCI: tegra194: Enable support for 256 Byte payload

Set 256 byte payload as the default in Device Control Register so as to
allow the PCIe sub-system to enable 256 byte max payload size when a
capable link partner is connected.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
V6:
* New addition in V6 based on Bjorn's review comment

 drivers/pci/controller/dwc/pcie-tegra194.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index 5f1798d37572..f82c70be72ef 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -839,6 +839,7 @@ static int tegra_pcie_dw_host_init(struct pcie_port *pp)
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct tegra_pcie_dw *pcie = to_tegra_pcie(pci);
 	u32 val;
+	u16 val_16;
 
 	pp->bridge->ops = &tegra_pci_ops;
 
@@ -846,6 +847,11 @@ static int tegra_pcie_dw_host_init(struct pcie_port *pp)
 		pcie->pcie_cap_base = dw_pcie_find_capability(&pcie->pci,
 							      PCI_CAP_ID_EXP);
 
+	val_16 = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_DEVCTL);
+	val_16 &= ~PCI_EXP_DEVCTL_PAYLOAD;
+	val_16 |= PCI_EXP_DEVCTL_PAYLOAD_256B;
+	dw_pcie_writew_dbi(pci, pcie->pcie_cap_base + PCI_EXP_DEVCTL, val_16);
+
 	val = dw_pcie_readl_dbi(pci, PCI_IO_BASE);
 	val &= ~(IO_BASE_IO_DECODE | IO_BASE_IO_DECODE_BIT8);
 	dw_pcie_writel_dbi(pci, PCI_IO_BASE, val);
@@ -1632,6 +1638,7 @@ static void pex_ep_event_pex_rst_deassert(struct tegra_pcie_dw *pcie)
 	struct device *dev = pcie->dev;
 	u32 val;
 	int ret;
+	u16 val_16;
 
 	if (pcie->ep_state == EP_STATE_ENABLED)
 		return;
@@ -1749,6 +1756,12 @@ static void pex_ep_event_pex_rst_deassert(struct tegra_pcie_dw *pcie)
 
 	pcie->pcie_cap_base = dw_pcie_find_capability(&pcie->pci,
 						      PCI_CAP_ID_EXP);
+
+	val_16 = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_DEVCTL);
+	val_16 &= ~PCI_EXP_DEVCTL_PAYLOAD;
+	val_16 |= PCI_EXP_DEVCTL_PAYLOAD_256B;
+	dw_pcie_writew_dbi(pci, pcie->pcie_cap_base + PCI_EXP_DEVCTL, val_16);
+
 	clk_set_rate(pcie->core_clk, GEN4_CORE_CLK_FREQ);
 
 	val = (ep->msi_mem_phys & MSIX_ADDR_MATCH_LOW_OFF_MASK);
-- 
2.17.1