[PATCH-for-9.1 v2 8/8] hw/misc/zynq_slcr: Only propagate clock changes when necessary

[Philippe Mathieu-Daudé]

Pass &bool to zynq_slcr_compute_clocks[_internal](), so we
can pass it to the clock_set() calls which might update it.
Then check it and only call zynq_slcr_propagate_clocks()
and clock_propagate() when necessary.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/misc/zynq_slcr.c | 39 ++++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 13 deletions(-)

diff --git a/hw/misc/zynq_slcr.c b/hw/misc/zynq_slcr.c
index e637798507..ad9c575137 100644
--- a/hw/misc/zynq_slcr.c
+++ b/hw/misc/zynq_slcr.c
@@ -269,7 +269,8 @@ static uint64_t zynq_slcr_compute_clock(const uint64_t 
periods[],
     zynq_slcr_compute_clock((plls), (state)->regs[reg], \
                             reg ## _ ## enable_field ## _SHIFT)
 
-static void zynq_slcr_compute_clocks_internal(ZynqSLCRState *s, uint64_t 
ps_clk)
+static void zynq_slcr_compute_clocks_internal(ZynqSLCRState *s, uint64_t 
ps_clk,
+                                              bool *changed)
 {
     uint64_t io_pll = zynq_slcr_compute_pll(ps_clk, s->regs[R_IO_PLL_CTRL]);
     uint64_t arm_pll = zynq_slcr_compute_pll(ps_clk, s->regs[R_ARM_PLL_CTRL]);
@@ -279,9 +280,9 @@ static void zynq_slcr_compute_clocks_internal(ZynqSLCRState 
*s, uint64_t ps_clk)
 
     /* compute uartX reference clocks */
     clock_set(s->uart0_ref_clk,
-              ZYNQ_COMPUTE_CLK(s, uart_mux, R_UART_CLK_CTRL, CLKACT0), NULL);
+              ZYNQ_COMPUTE_CLK(s, uart_mux, R_UART_CLK_CTRL, CLKACT0), 
changed);
     clock_set(s->uart1_ref_clk,
-              ZYNQ_COMPUTE_CLK(s, uart_mux, R_UART_CLK_CTRL, CLKACT1), NULL);
+              ZYNQ_COMPUTE_CLK(s, uart_mux, R_UART_CLK_CTRL, CLKACT1), 
changed);
 }
 
 /**
@@ -289,7 +290,7 @@ static void zynq_slcr_compute_clocks_internal(ZynqSLCRState 
*s, uint64_t ps_clk)
  * But do not propagate them further. Connected clocks
  * will not receive any updates (See zynq_slcr_compute_clocks())
  */
-static void zynq_slcr_compute_clocks(ZynqSLCRState *s)
+static void zynq_slcr_compute_clocks(ZynqSLCRState *s, bool *changed)
 {
     uint64_t ps_clk = clock_get(s->ps_clk);
 
@@ -298,7 +299,7 @@ static void zynq_slcr_compute_clocks(ZynqSLCRState *s)
         ps_clk = 0;
     }
 
-    zynq_slcr_compute_clocks_internal(s, ps_clk);
+    zynq_slcr_compute_clocks_internal(s, ps_clk, changed);
 }
 
 /**
@@ -315,9 +316,12 @@ static void zynq_slcr_propagate_clocks(ZynqSLCRState *s)
 static void zynq_slcr_ps_clk_callback(void *opaque, ClockEvent event)
 {
     ZynqSLCRState *s = (ZynqSLCRState *) opaque;
+    bool propagate = false;
 
-    zynq_slcr_compute_clocks(s);
-    zynq_slcr_propagate_clocks(s);
+    zynq_slcr_compute_clocks(s, &propagate);
+    if (propagate) {
+        zynq_slcr_propagate_clocks(s);
+    }
 }
 
 static void zynq_slcr_reset_init(Object *obj, ResetType type)
@@ -419,19 +423,25 @@ static void zynq_slcr_reset_init(Object *obj, ResetType 
type)
 static void zynq_slcr_reset_hold(Object *obj)
 {
     ZynqSLCRState *s = ZYNQ_SLCR(obj);
+    bool propagate = false;
 
     /* will disable all output clocks */
-    zynq_slcr_compute_clocks_internal(s, 0);
-    zynq_slcr_propagate_clocks(s);
+    zynq_slcr_compute_clocks_internal(s, 0, &propagate);
+    if (propagate) {
+        zynq_slcr_propagate_clocks(s);
+    }
 }
 
 static void zynq_slcr_reset_exit(Object *obj)
 {
     ZynqSLCRState *s = ZYNQ_SLCR(obj);
+    bool propagate = false;
 
     /* will compute output clocks according to ps_clk and registers */
-    zynq_slcr_compute_clocks_internal(s, clock_get(s->ps_clk));
-    zynq_slcr_propagate_clocks(s);
+    zynq_slcr_compute_clocks_internal(s, clock_get(s->ps_clk), &propagate);
+    if (propagate) {
+        zynq_slcr_propagate_clocks(s);
+    }
 }
 
 static bool zynq_slcr_check_offset(hwaddr offset, bool rnw)
@@ -516,6 +526,7 @@ static void zynq_slcr_write(void *opaque, hwaddr offset,
                           uint64_t val, unsigned size)
 {
     ZynqSLCRState *s = (ZynqSLCRState *)opaque;
+    bool propagate = false;
     offset /= 4;
 
     DB_PRINT("addr: %08" HWADDR_PRIx " data: %08" PRIx64 "\n", offset * 4, 
val);
@@ -569,8 +580,10 @@ static void zynq_slcr_write(void *opaque, hwaddr offset,
     case R_ARM_PLL_CTRL:
     case R_DDR_PLL_CTRL:
     case R_UART_CLK_CTRL:
-        zynq_slcr_compute_clocks(s);
-        zynq_slcr_propagate_clocks(s);
+        zynq_slcr_compute_clocks(s, &propagate);
+        if (propagate) {
+            zynq_slcr_propagate_clocks(s);
+        }
         break;
     }
 }
-- 
2.41.0