[PATCH] PCI: mediatek-gen3: Avoid PCIe resetting for Airoha EN7581 SoC

[Lorenzo Bianconi]

The PCIe controller available on the EN7581 SoC does not support reset
via the following lines:
- PCIE_MAC_RSTB
- PCIE_PHY_RSTB
- PCIE_BRG_RSTB
- PCIE_PE_RSTB

Introduce the reset callback in order to avoid resetting the PCIe port
for Airoha EN7581 SoC.

Tested-by: Hui Ma <hui.ma at airoha.com>
Signed-off-by: Lorenzo Bianconi <lorenzo at kernel.org>
---
 drivers/pci/controller/pcie-mediatek-gen3.c | 44 ++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 16 deletions(-)

diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
index 5c19abac74e8..9cea67e92d98 100644
--- a/drivers/pci/controller/pcie-mediatek-gen3.c
+++ b/drivers/pci/controller/pcie-mediatek-gen3.c
@@ -128,10 +128,12 @@ struct mtk_gen3_pcie;
 /**
  * struct mtk_gen3_pcie_pdata - differentiate between host generations
  * @power_up: pcie power_up callback
+ * @reset: pcie reset callback
  * @phy_resets: phy reset lines SoC data.
  */
 struct mtk_gen3_pcie_pdata {
 	int (*power_up)(struct mtk_gen3_pcie *pcie);
+	void (*reset)(struct mtk_gen3_pcie *pcie);
 	struct {
 		const char *id[MAX_NUM_PHY_RESETS];
 		int num_resets;
@@ -373,6 +375,28 @@ static void mtk_pcie_enable_msi(struct mtk_gen3_pcie *pcie)
 	writel_relaxed(val, pcie->base + PCIE_INT_ENABLE_REG);
 }
 
+static void mtk_pcie_reset(struct mtk_gen3_pcie *pcie)
+{
+	u32 val;
+
+	/* Assert all reset signals */
+	val = readl_relaxed(pcie->base + PCIE_RST_CTRL_REG);
+	val |= PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB;
+	writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
+
+	/*
+	 * Described in PCIe CEM specification sections 2.2 (PERST# Signal)
+	 * and 2.2.1 (Initial Power-Up (G3 to S0)).
+	 * The deassertion of PERST# should be delayed 100ms (TPVPERL)
+	 * for the power and clock to become stable.
+	 */
+	msleep(100);
+
+	/* De-assert reset signals */
+	val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB);
+	writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
+}
+
 static int mtk_pcie_startup_port(struct mtk_gen3_pcie *pcie)
 {
 	struct resource_entry *entry;
@@ -402,22 +426,9 @@ static int mtk_pcie_startup_port(struct mtk_gen3_pcie *pcie)
 	val |= PCIE_DISABLE_DVFSRC_VLT_REQ;
 	writel_relaxed(val, pcie->base + PCIE_MISC_CTRL_REG);
 
-	/* Assert all reset signals */
-	val = readl_relaxed(pcie->base + PCIE_RST_CTRL_REG);
-	val |= PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB;
-	writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
-
-	/*
-	 * Described in PCIe CEM specification sections 2.2 (PERST# Signal)
-	 * and 2.2.1 (Initial Power-Up (G3 to S0)).
-	 * The deassertion of PERST# should be delayed 100ms (TPVPERL)
-	 * for the power and clock to become stable.
-	 */
-	msleep(100);
-
-	/* De-assert reset signals */
-	val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB);
-	writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
+	/* Reset the PCIe port if requested by the hw */
+	if (pcie->soc->reset)
+		pcie->soc->reset(pcie);
 
 	/* Check if the link is up or not */
 	err = readl_poll_timeout(pcie->base + PCIE_LINK_STATUS_REG, val,
@@ -1207,6 +1218,7 @@ static const struct dev_pm_ops mtk_pcie_pm_ops = {
 
 static const struct mtk_gen3_pcie_pdata mtk_pcie_soc_mt8192 = {
 	.power_up = mtk_pcie_power_up,
+	.reset = mtk_pcie_reset,
 	.phy_resets = {
 		.id[0] = "phy",
 		.num_resets = 1,

---
base-commit: f2024903cb387971abdbc6398a430e735a9b394c
change-id: 20240920-pcie-en7581-rst-fix-8161658c13c4

Best regards,
-- 
Lorenzo Bianconi <lorenzo at kernel.org>