net: stmmac: use readl_poll_timeout() function in init_systime()

The init_systime() function use an open coded of readl_poll_timeout().
Replace the open coded handling with the proper function.
Signed-off-by: Dejin Zheng <zhengdejin5@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c

@@ -10,6 +10,7 @@
 *******************************************************************************/
 
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/delay.h>
 #include "common.h"
 #include "stmmac_ptp.h"
@@ -53,7 +54,6 @@ static void config_sub_second_increment(void __iomem *ioaddr,
 
 static int init_systime(void __iomem *ioaddr, u32 sec, u32 nsec)
 {
-	int limit;
 	u32 value;
 
 	writel(sec, ioaddr + PTP_STSUR);
@@ -64,16 +64,9 @@ static int init_systime(void __iomem *ioaddr, u32 sec, u32 nsec)
 	writel(value, ioaddr + PTP_TCR);
 
 	/* wait for present system time initialize to complete */
-	limit = 10;
-	while (limit--) {
-		if (!(readl(ioaddr + PTP_TCR) & PTP_TCR_TSINIT))
-			break;
-		mdelay(10);
-	}
-	if (limit < 0)
-		return -EBUSY;
-
-	return 0;
+	return readl_poll_timeout(ioaddr + PTP_TCR, value,
+				 !(value & PTP_TCR_TSINIT),
+				 10000, 100000);
 }
 
 static int config_addend(void __iomem *ioaddr, u32 addend)