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

Lorenzo Bianconi
2024-09-20T08:48:08Z

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@airoha.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@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@kernel.org>