enable cache in SAMD51

ports/atmel-samd/external_flash/qspi_flash.c

@@ -32,6 +32,7 @@
 #include "mpconfigboard.h" // for EXTERNAL_FLASH_QSPI_DUAL
 
 #include "external_flash/common_commands.h"
+#include "peripherals.h"
 #include "shared_dma.h"
 
 #include "atmel_start_pins.h"
@@ -55,6 +56,8 @@ bool spi_flash_command(uint8_t command) {
 }
 
 bool spi_flash_read_command(uint8_t command, uint8_t* response, uint32_t length) {
+    samd_peripherals_disable_and_clear_cache();
+
     QSPI->INSTRCTRL.bit.INSTR = command;
 
     QSPI->INSTRFRAME.reg = QSPI_INSTRFRAME_WIDTH_SINGLE_BIT_SPI |
@@ -63,6 +66,11 @@ bool spi_flash_read_command(uint8_t command, uint8_t* response, uint32_t length)
                            QSPI_INSTRFRAME_INSTREN |
                            QSPI_INSTRFRAME_DATAEN;
 
+    // Dummy read of INSTRFRAME needed to synchronize.
+    // See Instruction Transmission Flow Diagram, figure 37.9, page 995
+    // and Example 4, page 998, section 37.6.8.5.
+    (volatile uint32_t) QSPI->INSTRFRAME.reg;
+
     memcpy(response, (uint8_t *) QSPI_AHB, length);
 
     QSPI->CTRLA.reg = QSPI_CTRLA_ENABLE | QSPI_CTRLA_LASTXFER;
@@ -71,20 +79,28 @@ bool spi_flash_read_command(uint8_t command, uint8_t* response, uint32_t length)
 
     QSPI->INTFLAG.reg = QSPI_INTFLAG_INSTREND;
 
+    samd_peripherals_enable_cache();
+
     return true;
 }
 
 bool spi_flash_write_command(uint8_t command, uint8_t* data, uint32_t length) {
+    samd_peripherals_disable_and_clear_cache();
+
     QSPI->INSTRCTRL.bit.INSTR = command;
 
     QSPI->INSTRFRAME.reg = QSPI_INSTRFRAME_WIDTH_SINGLE_BIT_SPI |
                            QSPI_INSTRFRAME_ADDRLEN_24BITS |
                            QSPI_INSTRFRAME_TFRTYPE_WRITE |
-                           QSPI_INSTRFRAME_INSTREN;
+                           QSPI_INSTRFRAME_INSTREN |
+                           (data != NULL ? QSPI_INSTRFRAME_DATAEN : 0);
+
+    // Dummy read of INSTRFRAME needed to synchronize.
+    // See Instruction Transmission Flow Diagram, figure 37.9, page 995
+    // and Example 4, page 998, section 37.6.8.5.
+    (volatile uint32_t) QSPI->INSTRFRAME.reg;
 
     if (data != NULL) {
-        QSPI->INSTRFRAME.bit.DATAEN = true;
-
         memcpy((uint8_t *) QSPI_AHB, data, length);
     }
 
@@ -94,6 +110,8 @@ bool spi_flash_write_command(uint8_t command, uint8_t* data, uint32_t length) {
 
     QSPI->INTFLAG.reg = QSPI_INTFLAG_INSTREND;
 
+    samd_peripherals_enable_cache();
+
     return true;
 }
 
@@ -117,6 +135,8 @@ bool spi_flash_sector_command(uint8_t command, uint32_t address) {
 }
 
 bool spi_flash_write_data(uint32_t address, uint8_t* data, uint32_t length) {
+    samd_peripherals_disable_and_clear_cache();
+
     QSPI->INSTRCTRL.bit.INSTR = CMD_PAGE_PROGRAM;
     uint32_t mode = QSPI_INSTRFRAME_WIDTH_SINGLE_BIT_SPI;
 
@@ -137,10 +157,14 @@ bool spi_flash_write_data(uint32_t address, uint8_t* data, uint32_t length) {
 
     QSPI->INTFLAG.reg = QSPI_INTFLAG_INSTREND;
 
+    samd_peripherals_enable_cache();
+
     return true;
 }
 
 bool spi_flash_read_data(uint32_t address, uint8_t* data, uint32_t length) {
+    samd_peripherals_disable_and_clear_cache();
+
     #ifdef EXTERNAL_FLASH_QSPI_DUAL
     QSPI->INSTRCTRL.bit.INSTR = CMD_DUAL_READ;
     uint32_t mode = QSPI_INSTRFRAME_WIDTH_DUAL_OUTPUT;
@@ -167,6 +191,8 @@ bool spi_flash_read_data(uint32_t address, uint8_t* data, uint32_t length) {
 
     QSPI->INTFLAG.reg = QSPI_INTFLAG_INSTREND;
 
+    samd_peripherals_enable_cache();
+
     return true;
 }
 
@@ -183,7 +209,7 @@ void spi_flash_init(void) {
     // QSPI->BAUD.bit.BAUD = 32;
     // Super fast, may be unreliable when Saleae is connected to high speed lines.
     QSPI->BAUD.bit.BAUD = 2;
-    QSPI->CTRLB.reg = QSPI_CTRLB_MODE_MEMORY |
+    QSPI->CTRLB.reg = QSPI_CTRLB_MODE_MEMORY |        // Serial memory mode (map to QSPI_AHB)
                       QSPI_CTRLB_DATALEN_8BITS |
                       QSPI_CTRLB_CSMODE_LASTXFER;
 

ports/atmel-samd/samd51_peripherals.c

@@ -163,3 +163,15 @@ void samd_peripherals_adc_setup(struct adc_sync_descriptor *adc, Adc *instance)
     hri_adc_write_CALIB_BIASR2R_bf(instance, biasr2r);
     hri_adc_write_CALIB_BIASCOMP_bf(instance, biascomp);
 }
+
+// Turn off cache and invalidate all data in it.
+void samd_peripherals_disable_and_clear_cache(void) {
+    CMCC->CTRL.bit.CEN = 0;
+    while (CMCC->SR.bit.CSTS) {}
+    CMCC->MAINT0.bit.INVALL = 1;
+}
+
+// Enable cache
+void samd_peripherals_enable_cache(void) {
+    CMCC->CTRL.bit.CEN = 1;
+}

ports/atmel-samd/samd51_peripherals.h

@@ -35,4 +35,7 @@ uint8_t samd_peripherals_get_spi_dopo(uint8_t clock_pad, uint8_t mosi_pad);
 bool samd_peripherals_valid_spi_clock_pad(uint8_t clock_pad);
 void samd_peripherals_adc_setup(struct adc_sync_descriptor *adc, Adc *instance);
 
+void samd_peripherals_disable_and_clear_cache(void);
+void samd_peripherals_enable_cache(void);
+
 #endif  // MICROPY_INCLUDED_ATMEL_SAMD_SAMD51_PERIPHERALS_H

ports/atmel-samd/supervisor/port.c

@@ -57,6 +57,7 @@
 #include "shared-bindings/rtc/__init__.h"
 #include "clocks.h"
 #include "events.h"
+#include "peripherals.h"
 #include "shared_dma.h"
 #include "tick.h"
 
@@ -105,9 +106,47 @@ safe_mode_t port_init(void) {
     SUPC->BOD33.bit.ENABLE = 0;
     SUPC->BOD33.bit.LEVEL = 200;  // 2.7V: 1.5V + LEVEL * 6mV.
     SUPC->BOD33.bit.ENABLE = 1;
+
+    // MPU (Memory Protection Unit) setup.
+    // We hoped we could make the QSPI region be non-cachable with the MPU,
+    // but the CMCC doesn't seem to pay attention to the MPU settings.
+    // Leaving this code here disabled,
+    // because it was hard enough to figure out, and maybe there's
+    // a mistake that could make it work in the future.
+#if 0
+    // Designate QSPI memory mapped region as not cachable.
+
+    // Turn off MPU in case it is on.
+    MPU->CTRL = 0;
+    // Configure region 0.
+    MPU->RNR = 0;
+    // Region base: start of QSPI mapping area.
+    // QSPI region runs from 0x04000000 up to and not including 0x05000000: 16 megabytes
+    MPU->RBAR = QSPI_AHB;
+    MPU->RASR =
+        0b011 << MPU_RASR_AP_Pos |     // full read/write access for privileged and user mode
+        0b000 << MPU_RASR_TEX_Pos |    // caching not allowed, strongly ordered
+        1 << MPU_RASR_S_Pos |          // sharable
+        0 << MPU_RASR_C_Pos |          // not cachable
+        0 << MPU_RASR_B_Pos |          // not bufferable
+        0b10111 << MPU_RASR_SIZE_Pos | // 16MB region size
+        1 << MPU_RASR_ENABLE_Pos       // enable this region
+        ;
+    // Turn off regions 1-7.
+    for (uint32_t i = 1; i < 8; i ++) {
+        MPU->RNR = i;
+        MPU->RBAR = 0;
+        MPU->RASR = 0;
+    }
+
+    // Turn on MPU. Turn on PRIVDEFENA, which defines a default memory
+    // map for all privileged access, so we don't have to set up other regions
+    // besides QSPI.
+    MPU->CTRL = MPU_CTRL_PRIVDEFENA_Msk | MPU_CTRL_ENABLE_Msk;
 #endif
 
-
+    samd_peripherals_enable_cache();
+#endif
 
 // On power on start or external reset, set _ezero to the canary word. If it
 // gets killed, we boot in safe mode. _ezero is the boundary between statically