mtd: nand: zynq: Add a config option to use 1st stage bootloader timing

In legacy method, 1st stage bootloader was used to configure the HW
setting such as NAND timing. Hence, adding a config option in Zynq
NAND driver for the compatibility of device that using 1st stage
bootloder instead of U-boot SPL.

This commit is to add config option
CONFIG_NAND_ZYNQ_USE_BOOTLOADER1_TIMINGS that allow NAND driver use
timing values set by the 1st stage bootloader, instead of the hard-coded
values in the Zynq NAND driver.

Signed-off-by: Jeff Westfahl <jeff.westfahl@ni.com>
Signed-off-by: Wilson Lee <wilson.lee@ni.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Keng Soon Cheah <keng.soon.cheah@ni.com>
Cc: Chen Yee Chew <chen.yee.chew@ni.com>
Cc: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Scott Wood <oss@buserror.net>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

drivers/mtd/nand/Kconfig

@@ -165,6 +165,13 @@ config NAND_ZYNQ
 	  This enables Nand driver support for Nand flash controller
 	  found on Zynq SoC.
 
+config NAND_ZYNQ_USE_BOOTLOADER1_TIMINGS
+	bool "Enable use of 1st stage bootloader timing for NAND"
+	depends on NAND_ZYNQ
+	help
+	  This flag prevent U-boot reconfigure NAND flash controller and reuse
+	  the NAND timing from 1st stage bootloader.
+
 comment "Generic NAND options"
 
 # Enhance depends when converting drivers to Kconfig which use this config

drivers/mtd/nand/zynq_nand.c

@@ -35,6 +35,8 @@
 				(0x1 << 4)   |	/* Clear interrupt */ \
 				(0x1 << 6))	/* Disable ECC interrupt */
 
+#ifndef CONFIG_NAND_ZYNQ_USE_BOOTLOADER1_TIMINGS
+
 /* Assuming 50MHz clock (20ns cycle time) and 3V operation */
 #define ZYNQ_NAND_SET_CYCLES	((0x2 << 20) |	/* t_rr from nand_cycles */ \
 				(0x2 << 17)  |	/* t_ar from nand_cycles */ \
@@ -43,6 +45,7 @@
 				(0x2 << 8)   |	/* t_rea from nand_cycles */ \
 				(0x5 << 4)   |	/* t_wc from nand_cycles */ \
 				(0x5 << 0))	/* t_rc from nand_cycles */
+#endif
 
 
 #define ZYNQ_NAND_DIRECT_CMD	((0x4 << 23) |	/* Chip 0 from interface 1 */ \
@@ -245,8 +248,10 @@ static int zynq_nand_init_nand_flash(int option)
 
 	/* disable interrupts */
 	writel(ZYNQ_NAND_CLR_CONFIG, &zynq_nand_smc_base->cfr);
+#ifndef CONFIG_NAND_ZYNQ_USE_BOOTLOADER1_TIMINGS
 	/* Initialize the NAND interface by setting cycles and operation mode */
 	writel(ZYNQ_NAND_SET_CYCLES, &zynq_nand_smc_base->scr);
+#endif
 	if (option & NAND_BUSWIDTH_16)
 		writel(ZYNQ_NAND_SET_OPMODE_16BIT, &zynq_nand_smc_base->sor);
 	else