coresight: Avoid enable programming clock duplicately

The programming clock is enabled by AMBA bus driver before a dynamic
probe. As a result, a CoreSight driver may redundantly enable the same
clock.

To avoid this, add a check for device type and skip enabling the
programming clock for AMBA devices. The returned NULL pointer will be
tolerated by the drivers.

Fixes: 73d779a03a76 ("coresight: etm4x: Change etm4_platform_driver driver for MMIO devices")
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Tested-by: James Clark <james.clark@linaro.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20250731-arm_cs_fix_clock_v4-v6-6-1dfe10bb3f6f@arm.com

diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 1e652e157841955864a4bce00b2285efcad327aa..bb49080ec8f96bb23cab2efa23eb026646a3c4f4 100644 (file)
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -481,20 +481,23 @@ static inline bool is_coresight_device(void __iomem *base)
  * Returns:
  *
  * clk   - Clock is found and enabled
- * NULL  - Clock is controlled by firmware (ACPI device only)
+ * NULL  - Clock is controlled by firmware (ACPI device only) or when managed
+ *        by the AMBA bus driver instead
  * ERROR - Clock is found but failed to enable
  */
 static inline struct clk *coresight_get_enable_apb_pclk(struct device *dev)
 {
-       struct clk *pclk;
+       struct clk *pclk = NULL;
 
        /* Firmware controls clocks for an ACPI device. */
        if (has_acpi_companion(dev))
                return NULL;
 
-       pclk = devm_clk_get_optional_enabled(dev, "apb_pclk");
-       if (!pclk)
-               pclk = devm_clk_get_optional_enabled(dev, "apb");
+       if (!dev_is_amba(dev)) {
+               pclk = devm_clk_get_optional_enabled(dev, "apb_pclk");
+               if (!pclk)
+                       pclk = devm_clk_get_optional_enabled(dev, "apb");
+       }
 
        return pclk;
 }