[PATCH v6 08/12] i3c: dw-i3c-master: Add ACPI core clock frequency quirk

[Akhil R]

Some ACPI-enumerated devices like Tegra410 do not expose the controller
core clock through the clk framework. Unlike device tree, ACPI on Arm does
not model clock providers. The hardware is expected to have its clocks
enabled by firmware before the OS takes over.

Make the core clock optional and allow selected ACPI devices to provide the
core clock rate through the "clock-frequency" _DSD property when the core
clock is absent.

Resolve device quirks before acquiring the core clock so platforms without
the ACPI skip-clock quirk still fail probe immediately when the clock is
missing, before any MMIO access.

Signed-off-by: Akhil R <akhilrajeev@xxxxxxxxxx>
---
 drivers/i3c/master/dw-i3c-master.c | 50 +++++++++++++++++++++++-------
 1 file changed, 38 insertions(+), 12 deletions(-)

diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
index 29030fd9594a..3ec3ab1c13b4 100644
--- a/drivers/i3c/master/dw-i3c-master.c
+++ b/drivers/i3c/master/dw-i3c-master.c
@@ -242,6 +242,7 @@
 /* List of quirks */
 #define AMD_I3C_OD_PP_TIMING		BIT(1)
 #define DW_I3C_DISABLE_RUNTIME_PM_QUIRK	BIT(2)
+#define DW_I3C_ACPI_SKIP_CLK_RST	BIT(3)
 
 struct dw_i3c_cmd {
 	u32 cmd_lo;
@@ -556,13 +557,33 @@ static void dw_i3c_master_set_intr_regs(struct dw_i3c_master *master)
 	writel(IBI_REQ_REJECT_ALL, master->regs + IBI_MR_REQ_REJECT);
 }
 
+static unsigned long dw_i3c_master_get_core_rate(struct dw_i3c_master *master)
+{
+	unsigned int core_rate_prop;
+
+	if (master->core_clk)
+		return clk_get_rate(master->core_clk);
+
+	if (!(master->quirks & DW_I3C_ACPI_SKIP_CLK_RST)) {
+		dev_err(master->dev, "missing core clock\n");
+		return 0;
+	}
+
+	if (device_property_read_u32(master->dev, "clock-frequency", &core_rate_prop)) {
+		dev_err(master->dev, "missing clock-frequency property\n");
+		return 0;
+	}
+
+	return core_rate_prop;
+}
+
 static int dw_i3c_clk_cfg(struct dw_i3c_master *master)
 {
 	unsigned long core_rate, core_period;
 	u32 scl_timing;
 	u8 hcnt, lcnt;
 
-	core_rate = clk_get_rate(master->core_clk);
+	core_rate = dw_i3c_master_get_core_rate(master);
 	if (!core_rate)
 		return -EINVAL;
 
@@ -615,7 +636,7 @@ static int dw_i2c_clk_cfg(struct dw_i3c_master *master)
 	u16 hcnt, lcnt;
 	u32 scl_timing;
 
-	core_rate = clk_get_rate(master->core_clk);
+	core_rate = dw_i3c_master_get_core_rate(master);
 	if (!core_rate)
 		return -EINVAL;
 
@@ -1573,14 +1594,28 @@ int dw_i3c_common_probe(struct dw_i3c_master *master,
 
 	master->dev = &pdev->dev;
 
+	if (has_acpi_companion(&pdev->dev)) {
+		quirks = (unsigned long)device_get_match_data(&pdev->dev);
+	} else if (pdev->dev.of_node) {
+		drvdata = device_get_match_data(&pdev->dev);
+		if (drvdata)
+			quirks = drvdata->flags;
+	}
+	master->quirks = quirks;
+
 	master->regs = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(master->regs))
 		return PTR_ERR(master->regs);
 
-	master->core_clk = devm_clk_get_enabled(&pdev->dev, NULL);
+	master->core_clk = devm_clk_get_optional_enabled(&pdev->dev, NULL);
 	if (IS_ERR(master->core_clk))
 		return PTR_ERR(master->core_clk);
 
+	if (!master->core_clk && !(master->quirks & DW_I3C_ACPI_SKIP_CLK_RST)) {
+		dev_err(&pdev->dev, "missing core clock\n");
+		return -EINVAL;
+	}
+
 	master->pclk = devm_clk_get_optional_enabled(&pdev->dev, "pclk");
 	if (IS_ERR(master->pclk))
 		return PTR_ERR(master->pclk);
@@ -1636,15 +1671,6 @@ int dw_i3c_common_probe(struct dw_i3c_master *master,
 		master->has_ibi_data = true;
 	writel(thld_ctrl, master->regs + QUEUE_THLD_CTRL);
 
-	if (has_acpi_companion(&pdev->dev)) {
-		quirks = (unsigned long)device_get_match_data(&pdev->dev);
-	} else if (pdev->dev.of_node) {
-		drvdata = device_get_match_data(&pdev->dev);
-		if (drvdata)
-			quirks = drvdata->flags;
-	}
-	master->quirks = quirks;
-
 	/* Keep controller enabled by preventing runtime suspend */
 	if (master->quirks & DW_I3C_DISABLE_RUNTIME_PM_QUIRK)
 		pm_runtime_get_noresume(&pdev->dev);
-- 
2.43.0