1 files changed, 30 insertions, 20 deletions

diff --git a/drivers/clk/ingenic/tcu.c b/drivers/clk/ingenic/tcu.c
index 77acfbeb4830..d5544cbc5c48 100644
--- a/drivers/clk/ingenic/tcu.c
+++ b/drivers/clk/ingenic/tcu.c
@@ -31,6 +31,7 @@ struct ingenic_soc_info {
 	unsigned int num_channels;
 	bool has_ost;
 	bool has_tcu_clk;
+	bool allow_missing_tcu_clk;
 };
 
 struct ingenic_tcu_clk_info {
@@ -100,15 +101,11 @@ static bool ingenic_tcu_enable_regs(struct clk_hw *hw)
 	bool enabled = false;
 
 	/*
-	 * If the SoC has no global TCU clock, we must ungate the channel's
-	 * clock to be able to access its registers.
-	 * If we have a TCU clock, it will be enabled automatically as it has
-	 * been attached to the regmap.
+	 * According to the programming manual, a timer channel's registers can
+	 * only be accessed when the channel's stop bit is clear.
 	 */
-	if (!tcu->clk) {
-		enabled = !!ingenic_tcu_is_enabled(hw);
-		regmap_write(tcu->map, TCU_REG_TSCR, BIT(info->gate_bit));
-	}
+	enabled = !!ingenic_tcu_is_enabled(hw);
+	regmap_write(tcu->map, TCU_REG_TSCR, BIT(info->gate_bit));
 
 	return enabled;
 }
@@ -119,8 +116,7 @@ static void ingenic_tcu_disable_regs(struct clk_hw *hw)
 	const struct ingenic_tcu_clk_info *info = tcu_clk->info;
 	struct ingenic_tcu *tcu = tcu_clk->tcu;
 
-	if (!tcu->clk)
-		regmap_write(tcu->map, TCU_REG_TSSR, BIT(info->gate_bit));
+	regmap_write(tcu->map, TCU_REG_TSSR, BIT(info->gate_bit));
 }
 
 static u8 ingenic_tcu_get_parent(struct clk_hw *hw)
@@ -320,7 +316,8 @@ static const struct ingenic_soc_info jz4770_soc_info = {
 static const struct ingenic_soc_info x1000_soc_info = {
 	.num_channels = 8,
 	.has_ost = false, /* X1000 has OST, but it not belong TCU */
-	.has_tcu_clk = false,
+	.has_tcu_clk = true,
+	.allow_missing_tcu_clk = true,
 };
 
 static const struct of_device_id __maybe_unused ingenic_tcu_of_match[] __initconst = {
@@ -355,14 +352,27 @@ static int __init ingenic_tcu_probe(struct device_node *np)
 		tcu->clk = of_clk_get_by_name(np, "tcu");
 		if (IS_ERR(tcu->clk)) {
 			ret = PTR_ERR(tcu->clk);
-			pr_crit("Cannot get TCU clock\n");
-			goto err_free_tcu;
-		}
 
-		ret = clk_prepare_enable(tcu->clk);
-		if (ret) {
-			pr_crit("Unable to enable TCU clock\n");
-			goto err_put_clk;
+			/*
+			 * Old device trees for some SoCs did not include the
+			 * TCU clock because this driver (incorrectly) didn't
+			 * use it. In this case we complain loudly and attempt
+			 * to continue without the clock, which might work if
+			 * booting with workarounds like "clk_ignore_unused".
+			 */
+			if (tcu->soc_info->allow_missing_tcu_clk && ret == -EINVAL) {
+				pr_warn("TCU clock missing from device tree, please update your device tree\n");
+				tcu->clk = NULL;
+			} else {
+				pr_crit("Cannot get TCU clock from device tree\n");
+				goto err_free_tcu;
+			}
+		} else {
+			ret = clk_prepare_enable(tcu->clk);
+			if (ret) {
+				pr_crit("Unable to enable TCU clock\n");
+				goto err_put_clk;
+			}
 		}
 	}
 
@@ -432,10 +442,10 @@ err_unregister_timer_clocks:
 			clk_hw_unregister(tcu->clocks->hws[i]);
 	kfree(tcu->clocks);
 err_clk_disable:
-	if (tcu->soc_info->has_tcu_clk)
+	if (tcu->clk)
 		clk_disable_unprepare(tcu->clk);
 err_put_clk:
-	if (tcu->soc_info->has_tcu_clk)
+	if (tcu->clk)
 		clk_put(tcu->clk);
 err_free_tcu:
 	kfree(tcu);