pbio/include/pbdrv/cache.h: Rename EV3-specific macros

This makes it much more clear that this functionality is specific to
how Pybricks sets up the EV3.

Author: ArcaneNibble

lib/pbio/drv/block_device/block_device_ev3.c

@@ -755,8 +755,8 @@ pbio_error_t pbdrv_adc_get_ch(uint8_t ch, uint16_t *value) {
     uint16_t a, b;
     do {
         // Values for the requested channel are received several samples later.
-        a = PBDRV_UNCACHED(channel_data[ch + PBDRV_ADC_EV3_NUM_DELAY_SAMPLES]);
-        b = PBDRV_UNCACHED(channel_data[ch + PBDRV_ADC_EV3_NUM_DELAY_SAMPLES]);
+        a = PBDRV_EV3_UNCACHED(channel_data[ch + PBDRV_ADC_EV3_NUM_DELAY_SAMPLES]);
+        b = PBDRV_EV3_UNCACHED(channel_data[ch + PBDRV_ADC_EV3_NUM_DELAY_SAMPLES]);
     } while (a != b);
 
     // Mask the data to 10 bits

lib/pbio/drv/usb/usb_ev3.c

@@ -284,7 +284,7 @@ static uint32_t cppi_linking_ram[CPPI_DESC_COUNT];
 
 // Fill in the CPPI DMA descriptor to receive a packet
 static void usb_setup_rx_dma_desc(void) {
-    PBDRV_UNCACHED(cppi_descriptors[CPPI_DESC_RX]) = (usb_cppi_hpd_t) {
+    PBDRV_EV3_UNCACHED(cppi_descriptors[CPPI_DESC_RX]) = (usb_cppi_hpd_t) {
         .word0 = {
             .hostPktType = CPPI_HOST_PACKET_DESCRIPTOR_TYPE,
         },
@@ -308,7 +308,7 @@ static void usb_setup_rx_dma_desc(void) {
 
 // Fill in the CPPI DMA descriptor to send a packet
 static void usb_setup_tx_dma_desc(int tx_type, void *buf, uint32_t buf_len) {
-    PBDRV_UNCACHED(cppi_descriptors[tx_type]) = (usb_cppi_hpd_t) {
+    PBDRV_EV3_UNCACHED(cppi_descriptors[tx_type]) = (usb_cppi_hpd_t) {
         .word0 = {
             .hostPktType = CPPI_HOST_PACKET_DESCRIPTOR_TYPE,
             .pktLength = buf_len,
@@ -905,7 +905,7 @@ static pbio_error_t pbdrv_usb_ev3_process_thread(pbio_os_state_t *state, void *c
             // (which is technically allowed by the as-if rule).
             pbdrv_compiler_memory_barrier();
 
-            uint32_t usb_rx_sz = PBDRV_UNCACHED(cppi_descriptors[CPPI_DESC_RX].word0).pktLength;
+            uint32_t usb_rx_sz = PBDRV_EV3_UNCACHED(cppi_descriptors[CPPI_DESC_RX].word0).pktLength;
             pbio_pybricks_error_t result;
             bool usb_send_response = false;
             // Skip empty commands, or commands sent when previous response is still busy

lib/pbio/include/pbdrv/cache.h

@@ -14,11 +14,21 @@ void pbdrv_cache_prepare_before_dma(const void *buf, size_t sz);
 // by DMA peripherals. This invalidates the relevant cache lines.
 void pbdrv_cache_prepare_after_dma(const void *buf, size_t sz);
 
+// The EV3 MMU is configured to additionally map
+// VA 0xDxxxxxxx onto PA 0xCxxxxxxx, covering the DDR RAM region.
+// The 0xD alias is mapped as non-cacheable and non-bufferable
+// and can be used when data needs to be shared with bus-mastering
+// hardware peripherals. The 0xD region is unused in the physical
+// address map and lies at a convenient offset from the 0xC region.
+// The 0xC region, which is the region typically used to access RAM,
+// is cacheable and bufferable.
+#define PBDRV_EV3_UNCACHED_OFFSET   0x10000000
+
 // Accesses a variable via the uncached memory alias
-#define PBDRV_UNCACHED(x)           (*(volatile __typeof__(x) *)((uint32_t)(&(x)) + 0x10000000))
+#define PBDRV_EV3_UNCACHED(x)       (*(volatile __typeof__(x) *)((uintptr_t)(&(x)) + PBDRV_EV3_UNCACHED_OFFSET))
 
 // Gets the address of the uncached memory alias of a variable
-#define PBDRV_UNCACHED_ADDR(x)      ((__typeof__(x) *)((uint32_t)(&(x)) + 0x10000000))
+#define PBDRV_EV3_UNCACHED_ADDR(x)  ((__typeof__(x) *)((uintptr_t)(&(x)) + PBDRV_EV3_UNCACHED_OFFSET))
 
 // Cache line size
 #define PBDRV_CACHE_LINE_SZ         32

lib/pbio/platform/ev3/platform.c

@@ -727,7 +727,7 @@ static void mmu_init(void) {
     // Off-chip main DDR RAM, uncacheable mirror @ 0xD0000000
     for (unsigned int i = 0; i < SYSTEM_RAM_SZ_MB; i++) {
         uint32_t addr_phys = 0xC0000000 + i * MMU_SECTION_SZ;
-        uint32_t addr_virt = 0xD0000000 + i * MMU_SECTION_SZ;
+        uint32_t addr_virt = addr_phys + PBDRV_EV3_UNCACHED_OFFSET;
         l1_page_table[addr_virt >> MMU_SECTION_SHIFT] = MMU_L1_SECTION(addr_phys, 0, 1, 0, 0);
     }