linux-kernel - [PATCH v6 2/4] PCI: dwc: Always cache the maximum link speed value in dw_pcie::max_link

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Message-Id: <20240904-pci-qcom-gen4-stability-v6-2-ec39f7ae3f62@linaro.org>
Date: Wed, 04 Sep 2024 12:41:58 +0530
From: Manivannan Sadhasivam via B4 Relay <devnull+manivannan.sadhasivam.linaro.org@...nel.org>
To: Richard Zhu <hongxing.zhu@....com>, 
 Lucas Stach <l.stach@...gutronix.de>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Krzysztof Wilczyński <kw@...ux.com>, 
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, Jingoo Han <jingoohan1@...il.com>, 
 Chuanhua Lei <lchuanhua@...linear.com>, 
 Marek Vasut <marek.vasut+renesas@...il.com>, 
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Cc: linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 imx@...ts.linux.dev, linux-kernel@...r.kernel.org, 
 linux-renesas-soc@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
 abel.vesa@...aro.org, johan+linaro@...nel.org, 
 Shashank Babu Chinta Venkata <quic_schintav@...cinc.com>, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH v6 2/4] PCI: dwc: Always cache the maximum link speed value
 in dw_pcie::max_link_speed

From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Currently, dw_pcie::max_link_speed has a valid value only if the controller
driver restricts the maximum link speed in the driver or if the platform
does so in the devicetree using the 'max-link-speed' property.

But having the maximum supported link speed of the platform would be
helpful for the vendor drivers to configure any link specific settings.
So in the case of non-valid value in dw_pcie::max_link_speed, just cache
the hardware default value from Link Capability register.

While at it, let's also remove the 'max_link_speed' argument to the
dw_pcie_link_set_max_speed() function since the value can be retrieved
within the function.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/pci/controller/dwc/pcie-designware.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 86c49ba097c6..0704853daa85 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -687,16 +687,27 @@ void dw_pcie_upconfig_setup(struct dw_pcie *pci)
 }
 EXPORT_SYMBOL_GPL(dw_pcie_upconfig_setup);
 
-static void dw_pcie_link_set_max_speed(struct dw_pcie *pci, u32 max_link_speed)
+static void dw_pcie_link_set_max_speed(struct dw_pcie *pci)
 {
 	u32 cap, ctrl2, link_speed;
 	u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
 
 	cap = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
+
+	/*
+	 * Even if the platform doesn't want to limit the maximum link speed,
+	 * just cache the hardware default value so that the vendor drivers can
+	 * use it to do any link specific configuration.
+	 */
+	if (pci->max_link_speed < 0) {
+		pci->max_link_speed = FIELD_GET(PCI_EXP_LNKCAP_SLS, cap);
+		return;
+	}
+
 	ctrl2 = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCTL2);
 	ctrl2 &= ~PCI_EXP_LNKCTL2_TLS;
 
-	switch (pcie_link_speed[max_link_speed]) {
+	switch (pcie_link_speed[pci->max_link_speed]) {
 	case PCIE_SPEED_2_5GT:
 		link_speed = PCI_EXP_LNKCTL2_TLS_2_5GT;
 		break;
@@ -1058,8 +1069,7 @@ void dw_pcie_setup(struct dw_pcie *pci)
 {
 	u32 val;
 
-	if (pci->max_link_speed > 0)
-		dw_pcie_link_set_max_speed(pci, pci->max_link_speed);
+	dw_pcie_link_set_max_speed(pci);
 
 	/* Configure Gen1 N_FTS */
 	if (pci->n_fts[0]) {

-- 
2.25.1