Revert "ARM: socfpga: Remove socfpga_sdram_apply_static_cfg()

[Wolfgang Grandegger]

This reverts commit c5f4b805755912a3d2fe20f014b6b6ab0473bd73.

Conflicts:
	arch/arm/mach-socfpga/misc_gen5.c

Without socfpga_sdram_apply_static_cfg(), the system hangs when Linux
calls altvipfb2_start_hw() of the Intel Video and Image Processing(VIP)
Frame Buffer II driver (drivers/video/fbdev/altvipfb2.c), but only
after a power cycle (cold boot). The issue does not show up after a
soft reset (warm boot) and with v2018.11.

Signed-off-by: Wolfgang Grandegger <wg at aries-embedded.de>
CC: Marek Vasut <marex at denx.de>
CC: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>
---
 arch/arm/mach-socfpga/misc_gen5.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/arch/arm/mach-socfpga/misc_gen5.c b/arch/arm/mach-socfpga/misc_gen5.c
index 7209e8d..c1ecd92 100644
--- a/arch/arm/mach-socfpga/misc_gen5.c
+++ b/arch/arm/mach-socfpga/misc_gen5.c
@@ -216,6 +216,35 @@ int arch_early_init_r(void)
 static struct socfpga_sdr_ctrl *sdr_ctrl =
 	(struct socfpga_sdr_ctrl *)SDR_CTRLGRP_ADDRESS;
 
+static void socfpga_sdram_apply_static_cfg(void)
+{
+	const u32 applymask = 0x8;
+	u32 val = readl(&sdr_ctrl->static_cfg) | applymask;
+
+	/*
+	 * SDRAM staticcfg register specific:
+	 * When applying the register setting, the CPU must not access
+	 * SDRAM. Luckily for us, we can abuse i-cache here to help us
+	 * circumvent the SDRAM access issue. The idea is to make sure
+	 * that the code is in one full i-cache line by branching past
+	 * it and back. Once it is in the i-cache, we execute the core
+	 * of the code and apply the register settings.
+	 *
+	 * The code below uses 7 instructions, while the Cortex-A9 has
+	 * 32-byte cachelines, thus the limit is 8 instructions total.
+	 */
+	asm volatile(
+		".align	5			\n"
+		"	b	2f		\n"
+		"1:	str	%0,	[%1]	\n"
+		"	dsb			\n"
+		"	isb			\n"
+		"	b	3f		\n"
+		"2:	b	1b		\n"
+		"3:	nop			\n"
+	: : "r"(val), "r"(&sdr_ctrl->static_cfg) : "memory", "cc");
+}
+
 void do_bridge_reset(int enable, unsigned int mask)
 {
 	int i;
@@ -233,6 +262,7 @@ void do_bridge_reset(int enable, unsigned int mask)
 		writel(iswgrp_handoff[2],
 		       socfpga_get_sysmgr_addr() +
 		       SYSMGR_GEN5_FPGAINFGRP_MODULE);
+		socfpga_sdram_apply_static_cfg();
 		writel(iswgrp_handoff[3], &sdr_ctrl->fpgaport_rst);
 		writel(iswgrp_handoff[0],
 		       socfpga_get_rstmgr_addr() + RSTMGR_GEN5_BRGMODRST);
@@ -245,6 +275,7 @@ void do_bridge_reset(int enable, unsigned int mask)
 		writel(0, socfpga_get_sysmgr_addr() +
 		       SYSMGR_GEN5_FPGAINFGRP_MODULE);
 		writel(0, &sdr_ctrl->fpgaport_rst);
+		socfpga_sdram_apply_static_cfg();
 		writel(0x7, socfpga_get_rstmgr_addr() + RSTMGR_GEN5_BRGMODRST);
 		writel(1, &nic301_regs->remap);
 	}
-- 
1.9.1