stm32f7: sdram: correct sdram configuration as per micron sdram

Actually the sdram memory on stm32f746 discovery board is micron part
MT48LC_4M32_B2B5_6A. This patch does the modification required in the
device tree node & driver for the same.

Also we are passing here all the timing parameters in terms of clock
cycles, so no need to convert time(ns or ms) to cycles.

Signed-off-by: Vikas Manocha <vikas.manocha@st.com>
cc: Christophe KERELLO <christophe.kerello@st.com>

arch/arm/dts/stm32f746-disco.dts

@@ -106,12 +106,15 @@
 	status = "okay";
 
 	mr-nbanks = <1>;
-	/* sdram memory configuration from sdram datasheet IS42S16400J */
+	/* Memory configuration from sdram datasheet MT48LC_4M32_B2B5-6A */
 	bank1: bank@0 {
-	       st,sdram-control = /bits/ 8 <NO_COL_8 NO_ROW_12 MWIDTH_16 BANKS_2
-	       				    CAS_3 RD_BURST_EN RD_PIPE_DL_0>;
-	       st,sdram-timing = /bits/ 8 <TMRD_1 TXSR_60 TRAS_42 TRC_60 TRP_18
-	       				   TRCD_18>;
+	       st,sdram-control = /bits/ 8 <NO_COL_8 NO_ROW_12 MWIDTH_16 BANKS_4
+	       				    CAS_3 SDCLK_2 RD_BURST_EN
+					    RD_PIPE_DL_0>;
+	       st,sdram-timing = /bits/ 8 <TMRD_2 TXSR_6 TRAS_4 TRC_6 TWR_2
+	       				   TRP_2 TRCD_2>;
+		/* refcount = (64msec/total_row_sdram)*freq - 20 */
+	       st,sdram-refcount = < 1542 >;
        };
 };
 

drivers/ram/stm32_sdram.c

@@ -21,6 +21,7 @@ struct stm32_sdram_control {
 	u8 memory_width;
 	u8 no_banks;
 	u8 cas_latency;
+	u8 sdclk;
 	u8 rd_burst;
 	u8 rd_pipe_delay;
 };
@@ -31,51 +32,25 @@ struct stm32_sdram_timing {
 	u8 tras;
 	u8 trc;
 	u8 trp;
+	u8 twr;
 	u8 trcd;
 };
 struct stm32_sdram_params {
 	u8 no_sdram_banks;
 	struct stm32_sdram_control sdram_control;
 	struct stm32_sdram_timing sdram_timing;
+	u32 sdram_ref_count;
 };
-static inline u32 _ns2clk(u32 ns, u32 freq)
-{
-	u32 tmp = freq/1000000;
-	return (tmp * ns) / 1000;
-}
-
-#define NS2CLK(ns) (_ns2clk(ns, freq))
-
-#define SDRAM_TREF	(NS2CLK(64000000 / 8192) - 20)
 
 #define SDRAM_MODE_BL_SHIFT	0
 #define SDRAM_MODE_CAS_SHIFT	4
 #define SDRAM_MODE_BL		0
-#define SDRAM_MODE_CAS		3
-
-#define SDRAM_TRDL	12
 
 int stm32_sdram_init(struct udevice *dev)
 {
-	u32 freq;
-	u32 sdram_twr;
 	struct stm32_sdram_params *params = dev_get_platdata(dev);
 
-	/*
-	 * Get frequency for NS2CLK calculation.
-	 */
-	freq = clock_get(CLOCK_AHB) / CONFIG_SYS_RAM_FREQ_DIV;
-	debug("%s, sdram freq = %d\n", __func__, freq);
-
-	/* Last data in to row precharge, need also comply ineq on page 1648 */
-	sdram_twr = max(
-			max(SDRAM_TRDL, params->sdram_timing.tras
-			    - params->sdram_timing.trcd),
-			params->sdram_timing.trc - params->sdram_timing.trcd
-			- params->sdram_timing.trp
-		       );
-
-	writel(CONFIG_SYS_RAM_FREQ_DIV << FMC_SDCR_SDCLK_SHIFT
+	writel(params->sdram_control.sdclk << FMC_SDCR_SDCLK_SHIFT
 		| params->sdram_control.cas_latency << FMC_SDCR_CAS_SHIFT
 		| params->sdram_control.no_banks << FMC_SDCR_NB_SHIFT
 		| params->sdram_control.memory_width << FMC_SDCR_MWID_SHIFT
@@ -85,13 +60,13 @@ int stm32_sdram_init(struct udevice *dev)
 		| params->sdram_control.rd_burst << FMC_SDCR_RBURST_SHIFT,
 		&STM32_SDRAM_FMC->sdcr1);
 
-	writel(NS2CLK(params->sdram_timing.trcd) << FMC_SDTR_TRCD_SHIFT
-		| NS2CLK(params->sdram_timing.trp) << FMC_SDTR_TRP_SHIFT
-		| NS2CLK(sdram_twr) << FMC_SDTR_TWR_SHIFT
-		| NS2CLK(params->sdram_timing.trc) << FMC_SDTR_TRC_SHIFT
-		| NS2CLK(params->sdram_timing.tras) << FMC_SDTR_TRAS_SHIFT
-		| NS2CLK(params->sdram_timing.txsr) << FMC_SDTR_TXSR_SHIFT
-		| NS2CLK(params->sdram_timing.tmrd) << FMC_SDTR_TMRD_SHIFT,
+	writel(params->sdram_timing.trcd << FMC_SDTR_TRCD_SHIFT
+		| params->sdram_timing.trp << FMC_SDTR_TRP_SHIFT
+		| params->sdram_timing.twr << FMC_SDTR_TWR_SHIFT
+		| params->sdram_timing.trc << FMC_SDTR_TRC_SHIFT
+		| params->sdram_timing.tras << FMC_SDTR_TRAS_SHIFT
+		| params->sdram_timing.txsr << FMC_SDTR_TXSR_SHIFT
+		| params->sdram_timing.tmrd << FMC_SDTR_TMRD_SHIFT,
 		&STM32_SDRAM_FMC->sdtr1);
 
 	writel(FMC_SDCMR_BANK_1 | FMC_SDCMR_MODE_START_CLOCK,
@@ -110,7 +85,7 @@ int stm32_sdram_init(struct udevice *dev)
 	FMC_BUSY_WAIT();
 
 	writel(FMC_SDCMR_BANK_1 | (SDRAM_MODE_BL << SDRAM_MODE_BL_SHIFT
-	       | SDRAM_MODE_CAS << SDRAM_MODE_CAS_SHIFT)
+	       | params->sdram_control.cas_latency << SDRAM_MODE_CAS_SHIFT)
 	       << FMC_SDCMR_MODE_REGISTER_SHIFT | FMC_SDCMR_MODE_WRITE_MODE,
 	       &STM32_SDRAM_FMC->sdcmr);
 	udelay(100);
@@ -121,7 +96,7 @@ int stm32_sdram_init(struct udevice *dev)
 	FMC_BUSY_WAIT();
 
 	/* Refresh timer */
-	writel(SDRAM_TREF, &STM32_SDRAM_FMC->sdrtr);
+	writel((params->sdram_ref_count) << 1, &STM32_SDRAM_FMC->sdrtr);
 
 	return 0;
 }
@@ -142,12 +117,14 @@ static int stm32_fmc_ofdata_to_platdata(struct udevice *dev)
 					    sizeof(params->sdram_control));
 		if (ret)
 			return ret;
-
 		ret = fdtdec_get_byte_array(blob, node, "st,sdram-timing",
 					    (u8 *)&params->sdram_timing,
 					    sizeof(params->sdram_timing));
 		if (ret)
 			return ret;
+
+		params->sdram_ref_count = fdtdec_get_int(blob, node,
+						"st,sdram-refcount", 8196);
 	}
 
 	return 0;

include/configs/stm32f746-disco.h

@@ -16,7 +16,6 @@
  * Configuration of the external SDRAM memory
  */
 #define CONFIG_NR_DRAM_BANKS		1
-#define CONFIG_SYS_RAM_FREQ_DIV         2
 #define CONFIG_SYS_LOAD_ADDR		0xC0400000
 #define CONFIG_LOADADDR			0xC0400000
 

include/dt-bindings/memory/stm32-sdram.h

@@ -18,17 +18,20 @@
 #define CAS_1		0x1
 #define CAS_2		0x2
 #define CAS_3		0x3
+#define SDCLK_2		0x2
 #define RD_BURST_EN	0x1
 #define RD_BURST_DIS	0x0
 #define RD_PIPE_DL_0	0x0
 #define RD_PIPE_DL_1	0x1
 #define RD_PIPE_DL_2	0x2
 
-#define TMRD_1		0x1
-#define TXSR_60		60
-#define TRAS_42		42
-#define TRC_60		60
-#define TRP_18		18
-#define TRCD_18		18
+/* Timing = value +1 cycles */
+#define TMRD_2		(2 - 1)
+#define TXSR_6		(6 - 1)
+#define TRAS_4		(4 - 1)
+#define TRC_6		(6 - 1)
+#define TWR_2		(2 - 1)
+#define TRP_2		(2 - 1)
+#define TRCD_2		(2 - 1)
 
 #endif