ARM: at91: pm: disable RC oscillator in ULP0

Disable RC oscillator in ULP0 as datasheet specifies.
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>

arch/arm/mach-at91/pm_suspend.S

@@ -178,11 +178,46 @@ ENDPROC(at91_backup_mode)
 	orr	tmp1, tmp1, #AT91_PMC_KEY
 	str	tmp1, [pmc, #AT91_CKGR_MOR]
 
+	/* Save RC oscillator state */
+	ldr	tmp1, [pmc, #AT91_PMC_SR]
+	str	tmp1, .saved_osc_status
+	tst	tmp1, #AT91_PMC_MOSCRCS
+	bne	1f
+
+	/* Turn off RC oscillator */
+	ldr	tmp1, [pmc, #AT91_CKGR_MOR]
+	bic	tmp1, tmp1, #AT91_PMC_MOSCRCEN
+	bic	tmp1, tmp1, #AT91_PMC_KEY_MASK
+	orr	tmp1, tmp1, #AT91_PMC_KEY
+	str	tmp1, [pmc, #AT91_CKGR_MOR]
+
+	/* Wait main RC disabled done */
+2:	ldr	tmp1, [pmc, #AT91_PMC_SR]
+	tst	tmp1, #AT91_PMC_MOSCRCS
+	bne	2b
+
 	/* Wait for interrupt */
-	at91_cpu_idle
+1:	at91_cpu_idle
 
-	/* Turn on the crystal oscillator */
+	/* Restore RC oscillator state */
+	ldr	tmp1, .saved_osc_status
+	tst	tmp1, #AT91_PMC_MOSCRCS
+	beq	4f
+
+	/* Turn on RC oscillator */
 	ldr	tmp1, [pmc, #AT91_CKGR_MOR]
+	orr	tmp1, tmp1, #AT91_PMC_MOSCRCEN
+	bic	tmp1, tmp1, #AT91_PMC_KEY_MASK
+	orr	tmp1, tmp1, #AT91_PMC_KEY
+	str	tmp1, [pmc, #AT91_CKGR_MOR]
+
+	/* Wait main RC stabilization */
+3:	ldr	tmp1, [pmc, #AT91_PMC_SR]
+	tst	tmp1, #AT91_PMC_MOSCRCS
+	beq	3b
+
+	/* Turn on the crystal oscillator */
+4:	ldr	tmp1, [pmc, #AT91_CKGR_MOR]
 	orr	tmp1, tmp1, #AT91_PMC_MOSCEN
 	orr	tmp1, tmp1, #AT91_PMC_KEY
 	str	tmp1, [pmc, #AT91_CKGR_MOR]