[PATCH v4 2/2] PCI: mediatek-gen3: Add support for restricting link width

AngeloGioacchino Del Regno
2024-11-04T11:50:14Z

Add support for restricting the port's link width by specifying
the num-lanes devicetree property in the PCIe node.

The setting is done in the GEN_SETTINGS register (in the driver
named as PCIE_SETTING_REG), where each set bit in [11:8] activates
a set of lanes (from bits 11 to 8 respectively, x16/x8/x4/x2).

Reviewed-by: Fei Shao <fshao@chromium.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
drivers/pci/controller/pcie-mediatek-gen3.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
index c27beef75079..fa7f36a0284d 100644
--- a/drivers/pci/controller/pcie-mediatek-gen3.c
+++ b/drivers/pci/controller/pcie-mediatek-gen3.c
@@ -32,6 +32,7 @@
#define PCIE_BASE_CFG_SPEED GENMASK(15, 8)

#define PCIE_SETTING_REG 0x80
+#define PCIE_SETTING_LINK_WIDTH GENMASK(11, 8)
#define PCIE_SETTING_GEN_SUPPORT GENMASK(14, 12)
#define PCIE_PCI_IDS_1 0x9c
#define PCI_CLASS(class) (class << 8)
@@ -168,6 +169,7 @@ struct mtk_msi_set {
* @clks: PCIe clocks
* @num_clks: PCIe clocks count for this port
* @max_link_speed: Maximum link speed (PCIe Gen) for this port
+ * @num_lanes: Number of PCIe lanes for this port
* @irq: PCIe controller interrupt number
* @saved_irq_state: IRQ enable state saved at suspend time
* @irq_lock: lock protecting IRQ register access
@@ -189,6 +191,7 @@ struct mtk_gen3_pcie {
struct clk_bulk_data *clks;
int num_clks;
u8 max_link_speed;
+ u8 num_lanes;

int irq;
u32 saved_irq_state;
@@ -401,6 +404,14 @@ static int mtk_pcie_startup_port(struct mtk_gen3_pcie *pcie)
val |= FIELD_PREP(PCIE_SETTING_GEN_SUPPORT,
GENMASK(pcie->max_link_speed - 2, 0));
}
+ if (pcie->num_lanes) {
+ val &= ~PCIE_SETTING_LINK_WIDTH;
+
+ /* Zero means one lane, each bit activates x2/x4/x8/x16 */
+ if (pcie->num_lanes > 1)
+ val |= FIELD_PREP(PCIE_SETTING_LINK_WIDTH,
+ GENMASK(fls(pcie->num_lanes >> 2), 0));
+ };
writel_relaxed(val, pcie->base + PCIE_SETTING_REG);

/* Set Link Control 2 (LNKCTL2) speed restriction, if any */
@@ -838,6 +849,7 @@ static int mtk_pcie_parse_port(struct mtk_gen3_pcie *pcie)
struct device *dev = pcie->dev;
struct platform_device *pdev = to_platform_device(dev);
struct resource *regs;
+ u32 num_lanes;

regs = platform_get_resource_byname(pdev, IORESOURCE_MEM, "pcie-mac");
if (!regs)
@@ -883,6 +895,14 @@ static int mtk_pcie_parse_port(struct mtk_gen3_pcie *pcie)
return pcie->num_clks;
}

+ ret = of_property_read_u32(dev->of_node, "num-lanes", &num_lanes);
+ if (ret == 0) {
+ if (num_lanes == 0 || num_lanes > 16 || (num_lanes != 1 && num_lanes % 2))
+ dev_warn(dev, "Invalid num-lanes, using controller defaults\n");
+ else
+ pcie->num_lanes = num_lanes;
+ }
+
return 0;
}

--
2.46.1