[PATCH v5 2/5] PCI: qcom: Add .get_ltssm() helper

[Krishna Chaitanya Chundru]

For older targets like sc7280, we see reading DBI after sending PME
turn off message is causing NOC error.

To avoid unsafe DBI accesses, introduce qcom_pcie_get_ltssm() to retrieve
the LTSSM state. For newer platforms, the LTSSM state is read from the
PARF_LTSSM register, while older platforms continue to retrieve it from
ELBI_SYS_STTS.

This helper is used in place of direct DBI-based link state checks in
the D3cold path after sending PME turn-off message, ensuring the LTSSM
state can be queried safely even after DBI access is no longer valid.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru at oss.qualcomm.com>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index af6bf5cce65b..085300c1d1ec 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -71,6 +71,7 @@
 
 /* ELBI registers */
 #define ELBI_SYS_CTRL				0x04
+#define ELBI_SYS_STTS				0x08
 
 /* DBI registers */
 #define AXI_MSTR_RESP_COMP_CTRL0		0x818
@@ -131,6 +132,7 @@
 
 /* PARF_LTSSM register fields */
 #define LTSSM_EN				BIT(8)
+#define PARF_LTSSM_STATE_MASK			GENMASK(5, 0)
 
 /* PARF_NO_SNOOP_OVERRIDE register fields */
 #define WR_NO_SNOOP_OVERRIDE_EN			BIT(1)
@@ -145,6 +147,9 @@
 /* ELBI_SYS_CTRL register fields */
 #define ELBI_SYS_CTRL_LT_ENABLE			BIT(0)
 
+/* ELBI_SYS_STTS register fields */
+#define ELBI_SYS_STTS_LTSSM_STATE_MASK		GENMASK(17, 12)
+
 /* AXI_MSTR_RESP_COMP_CTRL0 register fields */
 #define CFG_REMOTE_RD_REQ_BRIDGE_SIZE_2K	0x4
 #define CFG_REMOTE_RD_REQ_BRIDGE_SIZE_4K	0x5
@@ -245,6 +250,7 @@ struct qcom_pcie_ops {
 	void (*deinit)(struct qcom_pcie *pcie);
 	void (*ltssm_enable)(struct qcom_pcie *pcie);
 	int (*config_sid)(struct qcom_pcie *pcie);
+	enum dw_pcie_ltssm (*get_ltssm)(struct qcom_pcie *pcie);
 };
 
  /**
@@ -428,6 +434,15 @@ static void qcom_pcie_2_1_0_ltssm_enable(struct qcom_pcie *pcie)
 	writel(val, pci->elbi_base + ELBI_SYS_CTRL);
 }
 
+static enum dw_pcie_ltssm qcom_pcie_2_1_0_get_ltssm(struct qcom_pcie *pcie)
+{
+	struct dw_pcie *pci = pcie->pci;
+	u32 val;
+
+	val = readl(pci->elbi_base + ELBI_SYS_STTS);
+	return (enum dw_pcie_ltssm)FIELD_GET(ELBI_SYS_STTS_LTSSM_STATE_MASK, val);
+}
+
 static int qcom_pcie_get_resources_2_1_0(struct qcom_pcie *pcie)
 {
 	struct qcom_pcie_resources_2_1_0 *res = &pcie->res.v2_1_0;
@@ -1260,6 +1275,19 @@ static bool qcom_pcie_link_up(struct dw_pcie *pci)
 	return val & PCI_EXP_LNKSTA_DLLLA;
 }
 
+static enum dw_pcie_ltssm qcom_pcie_get_ltssm(struct dw_pcie *pci)
+{
+	struct qcom_pcie *pcie = to_qcom_pcie(pci);
+	u32 val;
+
+	if (pcie->cfg->ops->ltssm_enable)
+		return pcie->cfg->ops->get_ltssm(pcie);
+
+	val = readl(pcie->parf + PARF_LTSSM);
+
+	return (enum dw_pcie_ltssm)FIELD_GET(PARF_LTSSM_STATE_MASK, val);
+}
+
 static void qcom_pcie_phy_power_off(struct qcom_pcie *pcie)
 {
 	struct qcom_pcie_port *port;
@@ -1385,6 +1413,7 @@ static const struct qcom_pcie_ops ops_2_1_0 = {
 	.post_init = qcom_pcie_post_init_2_1_0,
 	.deinit = qcom_pcie_deinit_2_1_0,
 	.ltssm_enable = qcom_pcie_2_1_0_ltssm_enable,
+	.get_ltssm = qcom_pcie_2_1_0_get_ltssm,
 };
 
 /* Qcom IP rev.: 1.0.0	Synopsys IP rev.: 4.11a */
@@ -1394,6 +1423,7 @@ static const struct qcom_pcie_ops ops_1_0_0 = {
 	.post_init = qcom_pcie_post_init_1_0_0,
 	.deinit = qcom_pcie_deinit_1_0_0,
 	.ltssm_enable = qcom_pcie_2_1_0_ltssm_enable,
+	.get_ltssm = qcom_pcie_2_1_0_get_ltssm,
 };
 
 /* Qcom IP rev.: 2.3.2	Synopsys IP rev.: 4.21a */
@@ -1512,6 +1542,7 @@ static const struct qcom_pcie_cfg cfg_fw_managed = {
 static const struct dw_pcie_ops dw_pcie_ops = {
 	.link_up = qcom_pcie_link_up,
 	.start_link = qcom_pcie_start_link,
+	.get_ltssm = qcom_pcie_get_ltssm,
 };
 
 static int qcom_pcie_icc_init(struct qcom_pcie *pcie)

-- 
2.34.1