ARM: at91: pm: avoid soft resetting AC DLL

[ Upstream commit cef8cdc0d0 ]

Do not soft reset AC DLL as controller is buggy and this operation my
introduce glitches in the controller leading to undefined behavior.

Fixes: f0bbf17958 ("ARM: at91: pm: add self-refresh support for sama7g5")
Depends-on: a02875c4cb ("ARM: at91: pm: fix self-refresh for sama7g5")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20221026124114.985876-2-claudiu.beznea@microchip.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/arm/mach-at91/pm_suspend.S

@@ -169,10 +169,15 @@ sr_ena_2:
 	cmp	tmp1, #UDDRC_STAT_SELFREF_TYPE_SW
 	bne	sr_ena_2
 
-	/* Put DDR PHY's DLL in bypass mode for non-backup modes. */
+	/* Disable DX DLLs for non-backup modes. */
 	cmp	r7, #AT91_PM_BACKUP
 	beq	sr_ena_3
 
+	/* Do not soft reset the AC DLL. */
+	ldr	tmp1, [r3, DDR3PHY_ACDLLCR]
+	bic	tmp1, tmp1, DDR3PHY_ACDLLCR_DLLSRST
+	str	tmp1, [r3, DDR3PHY_ACDLLCR]
+
 	/* Disable DX DLLs. */
 	ldr	tmp1, [r3, #DDR3PHY_DX0DLLCR]
 	orr	tmp1, tmp1, #DDR3PHY_DXDLLCR_DLLDIS

include/soc/at91/sama7-ddr.h

@@ -26,7 +26,10 @@
 #define	DDR3PHY_PGSR				(0x0C)		/* DDR3PHY PHY General Status Register */
 #define		DDR3PHY_PGSR_IDONE		(1 << 0)	/* Initialization Done */
 
-#define DDR3PHY_ACIOCR				(0x24)		/*  DDR3PHY AC I/O Configuration Register */
+#define	DDR3PHY_ACDLLCR				(0x14)		/* DDR3PHY AC DLL Control Register */
+#define		DDR3PHY_ACDLLCR_DLLSRST		(1 << 30)	/* DLL Soft Reset */
+
+#define DDR3PHY_ACIOCR				(0x24)		/* DDR3PHY AC I/O Configuration Register */
 #define		DDR3PHY_ACIOCR_CSPDD_CS0	(1 << 18)	/* CS#[0] Power Down Driver */
 #define		DDR3PHY_ACIOCR_CKPDD_CK0	(1 << 8)	/* CK[0] Power Down Driver */
 #define		DDR3PHY_ACIORC_ACPDD		(1 << 3)	/* AC Power Down Driver */