ARM: at91: spl: Adjust switching to oscillator for SAMA5D2

As said in 29.5.7 section of SAMA5D2 datasheet, before switching to
the crystal oscillator, a check must be carried out to ensure that
the oscillator is present and that its freqency is valid.

Signed-off-by: Wenyou Yang <wenyou.yang@microchip.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/arm/mach-at91/include/mach/at91_pmc.h

@@ -87,6 +87,8 @@ typedef struct at91_pmc {
 
 #define AT91_PMC_MCFR_MAINRDY		0x00010000
 #define AT91_PMC_MCFR_MAINF_MASK	0x0000FFFF
+#define AT91_PMC_MCFR_RCMEAS		0x00100000
+#define AT91_PMC_MCFR_CCSS_XTAL_OSC	0x01000000
 
 #define AT91_PMC_MCKR_CSS_SLOW		0x00000000
 #define AT91_PMC_MCKR_CSS_MAIN		0x00000001

arch/arm/mach-at91/spl_atmel.c

@@ -32,6 +32,20 @@ static void switch_to_main_crystal_osc(void)
 	while (!(readl(&pmc->sr) & AT91_PMC_IXR_MOSCS))
 		;
 
+#if defined(CONFIG_SAMA5D2)
+	/* Enable a measurement of the external oscillator */
+	tmp = readl(&pmc->mcfr);
+	tmp |= AT91_PMC_MCFR_CCSS_XTAL_OSC;
+	tmp |= AT91_PMC_MCFR_RCMEAS;
+	writel(tmp, &pmc->mcfr);
+
+	while (!(readl(&pmc->mcfr) & AT91_PMC_MCFR_MAINRDY))
+		;
+
+	if (!(readl(&pmc->mcfr) & AT91_PMC_MCFR_MAINF_MASK))
+		hang();
+#endif
+
 	tmp = readl(&pmc->mor);
 	tmp &= ~AT91_PMC_MOR_OSCBYPASS;
 	tmp &= ~AT91_PMC_MOR_KEY(0xff);
@@ -47,11 +61,13 @@ static void switch_to_main_crystal_osc(void)
 	while (!(readl(&pmc->sr) & AT91_PMC_IXR_MOSCSELS))
 		;
 
+#if !defined(CONFIG_SAMA5D2)
 	/* Wait until MAINRDY field is set to make sure main clock is stable */
 	while (!(readl(&pmc->mcfr) & AT91_PMC_MAINRDY))
 		;
+#endif
 
-#ifndef CONFIG_SAMA5D4
+#if !defined(CONFIG_SAMA5D4) && !defined(CONFIG_SAMA5D2)
 	tmp = readl(&pmc->mor);
 	tmp &= ~AT91_PMC_MOR_MOSCRCEN;
 	tmp &= ~AT91_PMC_MOR_KEY(0xff);