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authorPaul Selkirk <paul@psgd.org>2017-05-02 17:10:02 -0400
committerPaul Selkirk <paul@psgd.org>2017-05-02 17:10:02 -0400
commit1175ff63f2a8c4762692551403862f9f0789aef8 (patch)
treed7d004e639ffa35296b6c91a64711bcc34f63a9b /stm-sdram.c
parent716694ae77259e31526a6d64db867ced5c231ced (diff)
Merge branch 'init_cleanup' into no-rtos
Clean up Makefiles and initialization code.
Diffstat (limited to 'stm-sdram.c')
-rw-r--r--stm-sdram.c500
1 files changed, 216 insertions, 284 deletions
diff --git a/stm-sdram.c b/stm-sdram.c
index 58773e9..3ad17f0 100644
--- a/stm-sdram.c
+++ b/stm-sdram.c
@@ -1,284 +1,216 @@
-/*
- * stm-sdram.c
- * -----------
- * Functions concerning the 2x512 Mbit SDRAM working memory.
- *
- * Copyright (c) 2016, NORDUnet A/S All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
- * - Redistributions of source code must retain the above copyright notice,
- * this list of conditions and the following disclaimer.
- *
- * - Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- *
- * - Neither the name of the NORDUnet nor the names of its contributors may
- * be used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
- * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
- * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
- * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
- * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
- * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
- * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-#include "stm32f4xx_hal.h"
-#include "stm-init.h"
-#include "stm-sdram.h"
-#include "stm-fmc.h"
-#include "stm-led.h"
-
-/* Mode Register Bits */
-#define SDRAM_MODEREG_BURST_LENGTH_1 ((uint16_t)0x0000)
-#define SDRAM_MODEREG_BURST_LENGTH_2 ((uint16_t)0x0001)
-#define SDRAM_MODEREG_BURST_LENGTH_4 ((uint16_t)0x0002)
-#define SDRAM_MODEREG_BURST_LENGTH_8 ((uint16_t)0x0004)
-
-#define SDRAM_MODEREG_BURST_TYPE_SEQUENTIAL ((uint16_t)0x0000)
-#define SDRAM_MODEREG_BURST_TYPE_INTERLEAVED ((uint16_t)0x0008)
-
-#define SDRAM_MODEREG_CAS_LATENCY_2 ((uint16_t)0x0020)
-#define SDRAM_MODEREG_CAS_LATENCY_3 ((uint16_t)0x0030)
-
-#define SDRAM_MODEREG_OPERATING_MODE_STANDARD ((uint16_t)0x0000)
-
-#define SDRAM_MODEREG_WRITEBURST_MODE_PROGRAMMED ((uint16_t)0x0000)
-#define SDRAM_MODEREG_WRITEBURST_MODE_SINGLE ((uint16_t)0x0200)
-
-SDRAM_HandleTypeDef hsdram1;
-SDRAM_HandleTypeDef hsdram2;
-
-static void _sdram_init_gpio(void);
-static HAL_StatusTypeDef _sdram_init_fmc(void);
-static HAL_StatusTypeDef _sdram_init_params(SDRAM_HandleTypeDef *sdram1, SDRAM_HandleTypeDef *sdram2);
-
-
-HAL_StatusTypeDef sdram_init(void)
-{
- HAL_StatusTypeDef status;
- static int initialized = 0;
-
- if (initialized) {
- return HAL_OK;
- }
- initialized = 1;
-
- /* We rely on several things being set up by fmc_init() instead of duplicating all
- * that code here for independent FPGA/SDRAM FMC setup. This means the FPGA<->STM32
- * FMC bus can be used without the SDRAMs initialized, but the SDRAMs can't be
- * initialized withouth the FPGA<->STM32 FMC bus being set up too.
- */
- fmc_init();
-
- // configure FMC
- _sdram_init_gpio();
- status = _sdram_init_fmc();
- if (status != HAL_OK) return status;
-
- // configure SDRAM registers
- status = _sdram_init_params(&hsdram1, &hsdram2);
- if (status != HAL_OK) return status;
-
- return HAL_OK;
-}
-
-static void _sdram_init_gpio(void)
-{
- GPIO_InitTypeDef GPIO_InitStruct;
-
- /* The bulk of the FMC GPIO pins are set up in fmc_init_gpio().
- * This function just needs to enable the additional ones used
- * with the SDRAMs.
- */
- fmc_af_gpio(GPIOB, GPIO_PIN_5 | GPIO_PIN_6);
- fmc_af_gpio(GPIOC, GPIO_PIN_0 | GPIO_PIN_2 | GPIO_PIN_3);
- fmc_af_gpio(GPIOE, GPIO_PIN_0 | GPIO_PIN_1);
- fmc_af_gpio(GPIOF, GPIO_PIN_11);
- fmc_af_gpio(GPIOG, GPIO_PIN_8 | GPIO_PIN_15);
- fmc_af_gpio(GPIOI, GPIO_PIN_4 | GPIO_PIN_5);
-}
-
-static HAL_StatusTypeDef _sdram_init_fmc()
-{
- HAL_StatusTypeDef status;
- FMC_SDRAM_TimingTypeDef SdramTiming;
-
- /*
- * following settings are for -75E speed grade memory chip
- * clocked at only 90 MHz instead of the rated 133 MHz
- *
- * ExitSelfRefreshDelay: 67 ns @ 90 MHz is 6.03 cycles, so in theory
- * 6 can be used here, but let's be on the safe side
- *
- * WriteRecoveryTime: must be >= tRAS - tRCD (5 - 2 = 3 cycles),
- * and >= tRC - tRCD - tRP (8 - 2 - 2 = 4 cycles)
- */
- SdramTiming.LoadToActiveDelay = 2; // tMRD
- SdramTiming.ExitSelfRefreshDelay = 7; // (see above)
- SdramTiming.SelfRefreshTime = 5; // should be >= tRAS (5 cycles)
- SdramTiming.RowCycleDelay = 8; // tRC
- SdramTiming.WriteRecoveryTime = 4; // (see above)
- SdramTiming.RPDelay = 2; // tRP
- SdramTiming.RCDDelay = 2; // tRCD
-
- /*
- * configure the first bank
- */
-
- // memory type
- hsdram1.Instance = FMC_SDRAM_DEVICE;
-
- // bank
- hsdram1.Init.SDBank = FMC_SDRAM_BANK1;
-
- // settings for IS42S32160F
- hsdram1.Init.ColumnBitsNumber = FMC_SDRAM_COLUMN_BITS_NUM_9;
- hsdram1.Init.RowBitsNumber = FMC_SDRAM_ROW_BITS_NUM_13;
- hsdram1.Init.MemoryDataWidth = FMC_SDRAM_MEM_BUS_WIDTH_32;
- hsdram1.Init.InternalBankNumber = FMC_SDRAM_INTERN_BANKS_NUM_4;
- hsdram1.Init.CASLatency = FMC_SDRAM_CAS_LATENCY_2;
-
- // write protection not needed
- hsdram1.Init.WriteProtection = FMC_SDRAM_WRITE_PROTECTION_DISABLE;
-
- // memory clock is 90 MHz (HCLK / 2)
- hsdram1.Init.SDClockPeriod = FMC_SDRAM_CLOCK_PERIOD_2;
-
- // read burst not needed
- hsdram1.Init.ReadBurst = FMC_SDRAM_RBURST_DISABLE;
-
- // additional pipeline stages not neeed
- hsdram1.Init.ReadPipeDelay = FMC_SDRAM_RPIPE_DELAY_0;
-
- // call HAL layer
- status = HAL_SDRAM_Init(&hsdram1, &SdramTiming);
- if (status != HAL_OK) return status;
-
- /*
- * configure the second bank
- */
-
- // memory type
- hsdram2.Instance = FMC_SDRAM_DEVICE;
-
- // bank number
- hsdram2.Init.SDBank = FMC_SDRAM_BANK2;
-
- // settings for IS42S32160F
- hsdram2.Init.ColumnBitsNumber = FMC_SDRAM_COLUMN_BITS_NUM_9;
- hsdram2.Init.RowBitsNumber = FMC_SDRAM_ROW_BITS_NUM_13;
- hsdram2.Init.MemoryDataWidth = FMC_SDRAM_MEM_BUS_WIDTH_32;
- hsdram2.Init.InternalBankNumber = FMC_SDRAM_INTERN_BANKS_NUM_4;
- hsdram2.Init.CASLatency = FMC_SDRAM_CAS_LATENCY_2;
-
- // write protection not needed
- hsdram2.Init.WriteProtection = FMC_SDRAM_WRITE_PROTECTION_DISABLE;
-
- // memory clock is 90 MHz (HCLK / 2)
- hsdram2.Init.SDClockPeriod = FMC_SDRAM_CLOCK_PERIOD_2;
-
- // read burst not needed
- hsdram2.Init.ReadBurst = FMC_SDRAM_RBURST_DISABLE;
-
- // additional pipeline stages not neeed
- hsdram2.Init.ReadPipeDelay = FMC_SDRAM_RPIPE_DELAY_0;
-
- // call HAL layer
- return HAL_SDRAM_Init(&hsdram2, &SdramTiming);
-}
-
-static HAL_StatusTypeDef _sdram_init_params(SDRAM_HandleTypeDef *sdram1, SDRAM_HandleTypeDef *sdram2)
-{
- HAL_StatusTypeDef ok; // status
- FMC_SDRAM_CommandTypeDef cmd; // command
-
- /*
- * enable clocking
- */
- cmd.CommandMode = FMC_SDRAM_CMD_CLK_ENABLE;
- cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1_2;
- cmd.AutoRefreshNumber = 1;
- cmd.ModeRegisterDefinition = 0;
-
- HAL_Delay(1);
- ok = HAL_SDRAM_SendCommand(sdram1, &cmd, 1);
- if (ok != HAL_OK) return ok;
-
- /*
- * precharge all banks
- */
- cmd.CommandMode = FMC_SDRAM_CMD_PALL;
- cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1_2;
- cmd.AutoRefreshNumber = 1;
- cmd.ModeRegisterDefinition = 0;
-
- HAL_Delay(1);
- ok = HAL_SDRAM_SendCommand(sdram1, &cmd, 1);
- if (ok != HAL_OK) return ok;
-
-
- /*
- * send two auto-refresh commands in a row
- */
- cmd.CommandMode = FMC_SDRAM_CMD_AUTOREFRESH_MODE;
- cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1_2;
- cmd.AutoRefreshNumber = 1;
- cmd.ModeRegisterDefinition = 0;
-
- ok = HAL_SDRAM_SendCommand(sdram1, &cmd, 1);
- if (ok != HAL_OK) return ok;
-
- ok = HAL_SDRAM_SendCommand(sdram1, &cmd, 1);
- if (ok != HAL_OK) return ok;
-
-
- /*
- * load mode register
- */
- cmd.CommandMode = FMC_SDRAM_CMD_LOAD_MODE;
- cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1_2;
- cmd.AutoRefreshNumber = 1;
- cmd.ModeRegisterDefinition =
- SDRAM_MODEREG_BURST_LENGTH_1 |
- SDRAM_MODEREG_BURST_TYPE_SEQUENTIAL |
- SDRAM_MODEREG_CAS_LATENCY_2 |
- SDRAM_MODEREG_OPERATING_MODE_STANDARD |
- SDRAM_MODEREG_WRITEBURST_MODE_SINGLE ;
-
- ok = HAL_SDRAM_SendCommand(sdram1, &cmd, 1);
- if (ok != HAL_OK) return ok;
-
-
- /*
- * set number of consequtive auto-refresh commands
- * and program refresh rate
- *
- * RefreshRate = 64 ms / 8192 cyc = 7.8125 us/cyc
- *
- * RefreshCycles = 7.8125 us * 90 MHz = 703
- *
- * According to the formula on p.1665 of the reference manual,
- * we also need to subtract 20 from the value, so the target
- * refresh rate is 703 - 20 = 683.
- */
-
- ok = HAL_SDRAM_SetAutoRefreshNumber(sdram1, 8);
- if (ok != HAL_OK) return ok;
-
- HAL_SDRAM_ProgramRefreshRate(sdram1, 683);
- if (ok != HAL_OK) return ok;
-
- /*
- * done
- */
- return HAL_OK;
-}
+/*
+ * stm-sdram.c
+ * -----------
+ * Functions concerning the 2x512 Mbit SDRAM working memory.
+ *
+ * Copyright (c) 2016, NORDUnet A/S All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * - Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of the NORDUnet nor the names of its contributors may
+ * be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#include "stm-init.h"
+#include "stm-sdram.h"
+#include "stm-fmc.h"
+#include "stm-led.h"
+
+/* Mode Register Bits */
+#define SDRAM_MODEREG_BURST_LENGTH_1 ((uint16_t)0x0000)
+#define SDRAM_MODEREG_BURST_LENGTH_2 ((uint16_t)0x0001)
+#define SDRAM_MODEREG_BURST_LENGTH_4 ((uint16_t)0x0002)
+#define SDRAM_MODEREG_BURST_LENGTH_8 ((uint16_t)0x0004)
+
+#define SDRAM_MODEREG_BURST_TYPE_SEQUENTIAL ((uint16_t)0x0000)
+#define SDRAM_MODEREG_BURST_TYPE_INTERLEAVED ((uint16_t)0x0008)
+
+#define SDRAM_MODEREG_CAS_LATENCY_2 ((uint16_t)0x0020)
+#define SDRAM_MODEREG_CAS_LATENCY_3 ((uint16_t)0x0030)
+
+#define SDRAM_MODEREG_OPERATING_MODE_STANDARD ((uint16_t)0x0000)
+
+#define SDRAM_MODEREG_WRITEBURST_MODE_PROGRAMMED ((uint16_t)0x0000)
+#define SDRAM_MODEREG_WRITEBURST_MODE_SINGLE ((uint16_t)0x0200)
+
+static SDRAM_HandleTypeDef hsdram1;
+static SDRAM_HandleTypeDef hsdram2;
+
+static void _sdram_init_gpio(void);
+static void _sdram_init_fmc(void);
+static void _sdram_init_params(void);
+
+void sdram_init(void)
+{
+ static int initialized = 0;
+ if (initialized) return;
+ initialized = 1;
+
+ /* We rely on several things being set up by fmc_init() instead of duplicating all
+ * that code here for independent FPGA/SDRAM FMC setup. This means the FPGA<->STM32
+ * FMC bus can be used without the SDRAMs initialized, but the SDRAMs can't be
+ * initialized withouth the FPGA<->STM32 FMC bus being set up too.
+ */
+ fmc_init();
+
+ /* configure FMC */
+ _sdram_init_gpio();
+ _sdram_init_fmc();
+
+ /* configure SDRAM registers */
+ _sdram_init_params();
+}
+
+static void _sdram_init_gpio(void)
+{
+ GPIO_InitTypeDef GPIO_InitStruct;
+
+ /* The bulk of the FMC GPIO pins are set up in fmc_init_gpio().
+ * This function just needs to enable the additional ones used
+ * with the SDRAMs.
+ */
+ fmc_af_gpio(GPIOB, GPIO_PIN_5 | GPIO_PIN_6);
+ fmc_af_gpio(GPIOC, GPIO_PIN_0 | GPIO_PIN_2 | GPIO_PIN_3);
+ fmc_af_gpio(GPIOE, GPIO_PIN_0 | GPIO_PIN_1);
+ fmc_af_gpio(GPIOF, GPIO_PIN_11);
+ fmc_af_gpio(GPIOG, GPIO_PIN_8 | GPIO_PIN_15);
+ fmc_af_gpio(GPIOI, GPIO_PIN_4 | GPIO_PIN_5);
+}
+
+static void _sdram_config_bank(SDRAM_HandleTypeDef *hsdram, uint32_t SDBank, FMC_SDRAM_TimingTypeDef *SdramTiming)
+{
+ /* memory type */
+ hsdram->Instance = FMC_SDRAM_DEVICE;
+
+ /* bank */
+ hsdram->Init.SDBank = SDBank;
+
+ /* settings for IS42S32160F */
+ hsdram->Init.ColumnBitsNumber = FMC_SDRAM_COLUMN_BITS_NUM_9;
+ hsdram->Init.RowBitsNumber = FMC_SDRAM_ROW_BITS_NUM_13;
+ hsdram->Init.MemoryDataWidth = FMC_SDRAM_MEM_BUS_WIDTH_32;
+ hsdram->Init.InternalBankNumber = FMC_SDRAM_INTERN_BANKS_NUM_4;
+ hsdram->Init.CASLatency = FMC_SDRAM_CAS_LATENCY_2;
+
+ /* write protection not needed */
+ hsdram->Init.WriteProtection = FMC_SDRAM_WRITE_PROTECTION_DISABLE;
+
+ /* memory clock is 90 MHz (HCLK / 2) */
+ hsdram->Init.SDClockPeriod = FMC_SDRAM_CLOCK_PERIOD_2;
+
+ /* read burst not needed */
+ hsdram->Init.ReadBurst = FMC_SDRAM_RBURST_DISABLE;
+
+ /* additional pipeline stages not neeed */
+ hsdram->Init.ReadPipeDelay = FMC_SDRAM_RPIPE_DELAY_0;
+
+ /* call HAL layer */
+ HAL_SDRAM_Init(hsdram, SdramTiming);
+}
+
+static void _sdram_init_fmc(void)
+{
+ FMC_SDRAM_TimingTypeDef SdramTiming;
+
+ /*
+ * following settings are for -75E speed grade memory chip
+ * clocked at only 90 MHz instead of the rated 133 MHz
+ *
+ * ExitSelfRefreshDelay: 67 ns @ 90 MHz is 6.03 cycles, so in theory
+ * 6 can be used here, but let's be on the safe side
+ *
+ * WriteRecoveryTime: must be >= tRAS - tRCD (5 - 2 = 3 cycles),
+ * and >= tRC - tRCD - tRP (8 - 2 - 2 = 4 cycles)
+ */
+ SdramTiming.LoadToActiveDelay = 2; // tMRD
+ SdramTiming.ExitSelfRefreshDelay = 7; // (see above)
+ SdramTiming.SelfRefreshTime = 5; // should be >= tRAS (5 cycles)
+ SdramTiming.RowCycleDelay = 8; // tRC
+ SdramTiming.WriteRecoveryTime = 4; // (see above)
+ SdramTiming.RPDelay = 2; // tRP
+ SdramTiming.RCDDelay = 2; // tRCD
+
+ /* configure the first bank */
+ _sdram_config_bank(&hsdram1, FMC_SDRAM_BANK1, &SdramTiming);
+
+ /* configure the second bank */
+ _sdram_config_bank(&hsdram2, FMC_SDRAM_BANK2, &SdramTiming);
+}
+
+static void _sdram_init_params(void)
+{
+ FMC_SDRAM_CommandTypeDef cmd;
+
+ /* enable clocking */
+ cmd.CommandMode = FMC_SDRAM_CMD_CLK_ENABLE;
+ cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1_2;
+ cmd.AutoRefreshNumber = 1;
+ cmd.ModeRegisterDefinition = 0;
+ HAL_Delay(1);
+ HAL_SDRAM_SendCommand(&hsdram1, &cmd, 1);
+
+ /* precharge all banks */
+ cmd.CommandMode = FMC_SDRAM_CMD_PALL;
+ cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1_2;
+ cmd.AutoRefreshNumber = 1;
+ cmd.ModeRegisterDefinition = 0;
+ HAL_Delay(1);
+ HAL_SDRAM_SendCommand(&hsdram1, &cmd, 1);
+
+ /* send two auto-refresh commands in a row */
+ cmd.CommandMode = FMC_SDRAM_CMD_AUTOREFRESH_MODE;
+ cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1_2;
+ cmd.AutoRefreshNumber = 1;
+ cmd.ModeRegisterDefinition = 0;
+ HAL_SDRAM_SendCommand(&hsdram1, &cmd, 1);
+ HAL_SDRAM_SendCommand(&hsdram1, &cmd, 1);
+
+ /* load mode register */
+ cmd.CommandMode = FMC_SDRAM_CMD_LOAD_MODE;
+ cmd.CommandTarget = FMC_SDRAM_CMD_TARGET_BANK1_2;
+ cmd.AutoRefreshNumber = 1;
+ cmd.ModeRegisterDefinition =
+ SDRAM_MODEREG_BURST_LENGTH_1 |
+ SDRAM_MODEREG_BURST_TYPE_SEQUENTIAL |
+ SDRAM_MODEREG_CAS_LATENCY_2 |
+ SDRAM_MODEREG_OPERATING_MODE_STANDARD |
+ SDRAM_MODEREG_WRITEBURST_MODE_SINGLE ;
+ HAL_SDRAM_SendCommand(&hsdram1, &cmd, 1);
+
+ /*
+ * set number of consequtive auto-refresh commands
+ * and program refresh rate
+ *
+ * RefreshRate = 64 ms / 8192 cyc = 7.8125 us/cyc
+ *
+ * RefreshCycles = 7.8125 us * 90 MHz = 703
+ *
+ * According to the formula on p.1665 of the reference manual,
+ * we also need to subtract 20 from the value, so the target
+ * refresh rate is 703 - 20 = 683.
+ */
+
+ HAL_SDRAM_SetAutoRefreshNumber(&hsdram1, 8);
+
+ HAL_SDRAM_ProgramRefreshRate(&hsdram1, 683);
+}