[upstream backport] RMT High-priority Interrupt driver - solves flickering problems on esp32, esp32-S2 and esp32-S3

lib/NeoESP32RmtHI/library.json

@@ -0,0 +1,12 @@
+{
+  "name": "NeoESP32RmtHI",
+  "build": { "libArchive": false },
+  "platforms": ["espressif32"],
+  "dependencies": [
+    {
+      "owner": "makuna",      
+      "name": "NeoPixelBus",
+      "version": "^2.7.9"
+    }
+  ]
+}  

lib/NeoESP32RmtHI/src/NeoEsp32RmtHI.S

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+/* RMT ISR shim
+ * Bridges from a high-level interrupt to the C++ code.
+ *
+ * This code is largely derived from Espressif's 'hli_vector.S' Bluetooth ISR.
+ *
+ */
+
+#if defined(__XTENSA__) && defined(ESP32) && !defined(CONFIG_BTDM_CTRL_HLI)
+#if !defined(WLED_USE_SHARED_RMT)  && !defined(__riscv) && defined(ARDUINO_ARCH_ESP32) && (ESP_IDF_VERSION_MAJOR >= 4) // WLEDMM don't compile this file on unsupported platforms
+
+#include <freertos/xtensa_context.h>
+#include "sdkconfig.h"
+#include "soc/soc.h"
+
+/* If the Bluetooth driver has hooked the high-priority interrupt, we piggyback on it and don't need this. */
+#ifndef CONFIG_BTDM_CTRL_HLI
+
+/*
+   Select interrupt based on system check level
+   - Base ESP32: could be 4 or 5, depends on platform config
+   - S2: 5
+   - S3: 5
+*/
+
+#if CONFIG_ESP_SYSTEM_CHECK_INT_LEVEL_5
+/* Use level 4 */
+#define RFI_X               4
+#define xt_highintx         xt_highint4
+#else /* !CONFIG_ESP_SYSTEM_CHECK_INT_LEVEL_5 */
+/* Use level 5 */
+#define RFI_X               5
+#define xt_highintx         xt_highint5
+#endif /* CONFIG_ESP_SYSTEM_CHECK_INT_LEVEL_5 */
+
+// Register map, based on interrupt level
+#define EPC_X               (EPC + RFI_X)
+#define EXCSAVE_X           (EXCSAVE + RFI_X)
+
+// The sp mnemonic is used all over in ESP's assembly, though I'm not sure where it's expected to be defined?
+#define sp a1
+
+/* Interrupt stack size, for C code. */
+#define RMT_INTR_STACK_SIZE  512
+
+/* Save area for the CPU state:
+ * - 64 words for the general purpose registers
+ * - 7 words for some of the special registers:
+ *   - WINDOWBASE, WINDOWSTART — only WINDOWSTART is truly needed
+ *   - SAR, LBEG, LEND, LCOUNT — since the C code might use these
+ *   - EPC1 — since the C code might cause window overflow exceptions
+ * This is not laid out as standard exception frame structure
+ * for simplicity of the save/restore code.
+ */
+#define REG_FILE_SIZE         (64 * 4)
+#define SPECREG_OFFSET        REG_FILE_SIZE
+#define SPECREG_SIZE          (7 * 4)
+#define REG_SAVE_AREA_SIZE    (SPECREG_OFFSET + SPECREG_SIZE)
+
+    .data
+_rmt_intr_stack:
+    .space      RMT_INTR_STACK_SIZE
+_rmt_save_ctx:
+    .space      REG_SAVE_AREA_SIZE
+
+    .section .iram1,"ax"
+    .global     xt_highintx
+    .type       xt_highintx,@function
+    .align      4
+
+xt_highintx:
+
+    movi    a0, _rmt_save_ctx
+    /* save 4 lower registers */
+    s32i    a1, a0, 4
+    s32i    a2, a0, 8
+    s32i    a3, a0, 12
+    rsr     a2, EXCSAVE_X  /* holds the value of a0 */
+    s32i    a2, a0, 0
+
+    /* Save special registers */
+    addi    a0, a0, SPECREG_OFFSET
+    rsr     a2, WINDOWBASE
+    s32i    a2, a0, 0
+    rsr     a2, WINDOWSTART
+    s32i    a2, a0, 4
+    rsr     a2, SAR
+    s32i    a2, a0, 8
+    #if XCHAL_HAVE_LOOPS
+    rsr     a2, LBEG
+    s32i    a2, a0, 12
+    rsr     a2, LEND
+    s32i    a2, a0, 16
+    rsr     a2, LCOUNT
+    s32i    a2, a0, 20
+    #endif
+    rsr     a2, EPC1
+    s32i    a2, a0, 24
+
+    /* disable exception mode, window overflow */
+    movi    a0, PS_INTLEVEL(RFI_X+1) | PS_EXCM
+    wsr     a0, PS
+    rsync
+
+    /* Save the remaining physical registers.
+     * 4 registers are already saved, which leaves 60 registers to save.
+     * (FIXME: consider the case when the CPU is configured with physical 32 registers)
+     * These 60 registers are saved in 5 iterations, 12 registers at a time.
+     */
+    movi    a1, 5
+    movi    a3, _rmt_save_ctx + 4 * 4
+
+    /* This is repeated 5 times, each time the window is shifted by 12 registers.
+     * We come here with a1 = downcounter, a3 = save pointer, a2 and a0 unused.
+     */
+1:
+    s32i    a4, a3, 0
+    s32i    a5, a3, 4
+    s32i    a6, a3, 8
+    s32i    a7, a3, 12
+    s32i    a8, a3, 16
+    s32i    a9, a3, 20
+    s32i    a10, a3, 24
+    s32i    a11, a3, 28
+    s32i    a12, a3, 32
+    s32i    a13, a3, 36
+    s32i    a14, a3, 40
+    s32i    a15, a3, 44
+
+    /* We are about to rotate the window, so that a12-a15 will become the new a0-a3.
+     * Copy a0-a3 to a12-15 to still have access to these values.
+     * At the same time we can decrement the counter and adjust the save area pointer
+     */
+
+    /* a0 is constant (_rmt_save_ctx), no need to copy */
+    addi    a13, a1, -1  /* copy and decrement the downcounter */
+    /* a2 is scratch so no need to copy */
+    addi    a15, a3, 48  /* copy and adjust the save area pointer */
+    beqz    a13, 2f      /* have saved all registers ? */
+    rotw    3            /* rotate the window and go back */
+    j       1b
+
+    /* the loop is complete */
+2:
+    rotw 4      /* this brings us back to the original window */
+    /* a0 still points to _rmt_save_ctx */
+
+    /* Can clear WINDOWSTART now, all registers are saved */
+    rsr     a2, WINDOWBASE
+    /* WINDOWSTART = (1 << WINDOWBASE) */
+    movi    a3, 1
+    ssl     a2
+    sll     a3, a3
+    wsr     a3, WINDOWSTART
+
+_highint_stack_switch:
+    movi    a0, 0
+    movi    sp, _rmt_intr_stack + RMT_INTR_STACK_SIZE - 16
+    s32e    a0, sp, -12         /* For GDB: set null SP */
+    s32e    a0, sp, -16         /* For GDB: set null PC */
+    movi    a0, _highint_stack_switch     /* For GDB: cosmetics, for the frame where stack switch happened */
+
+    /* Set up PS for C, disable all interrupts except NMI and debug, and clear EXCM. */
+    movi    a6, PS_INTLEVEL(RFI_X) | PS_UM | PS_WOE
+    wsr     a6, PS
+    rsync
+
+    /* Call C handler */
+    mov     a6, sp
+    call4   NeoEsp32RmtMethodIsr
+
+    l32e    sp, sp, -12                     /* switch back to the original stack */
+
+    /* Done with C handler; re-enable exception mode, disabling window overflow */
+    movi    a2, PS_INTLEVEL(RFI_X+1) | PS_EXCM    /* TOCHECK */
+    wsr     a2, PS
+    rsync
+
+    /* Restore the special registers.
+     * WINDOWSTART will be restored near the end.
+     */
+    movi    a0, _rmt_save_ctx + SPECREG_OFFSET
+    l32i    a2, a0, 8
+    wsr     a2, SAR
+    #if XCHAL_HAVE_LOOPS
+    l32i    a2, a0, 12
+    wsr     a2, LBEG
+    l32i    a2, a0, 16
+    wsr     a2, LEND
+    l32i    a2, a0, 20
+    wsr     a2, LCOUNT
+    #endif
+    l32i    a2, a0, 24
+    wsr     a2, EPC1
+
+    /* Restoring the physical registers.
+     * This is the reverse to the saving process above.
+     */
+
+    /* Rotate back to the final window, then start loading 12 registers at a time,
+     * in 5 iterations.
+     * Again, a1 is the downcounter and a3 is the save area pointer.
+     * After each rotation, a1 and a3 are copied from a13 and a15.
+     * To simplify the loop, we put the initial values into a13 and a15.
+     */
+    rotw     -4
+    movi    a15, _rmt_save_ctx + 64 * 4  /* point to the end of the save area */
+    movi    a13, 5
+
+1:
+    /* Copy a1 and a3 from their previous location,
+     * at the same time decrementing and adjusting the save area pointer.
+     */
+    addi    a1, a13, -1
+    addi    a3, a15, -48
+
+    /* Load 12 registers */
+    l32i    a4, a3, 0
+    l32i    a5, a3, 4
+    l32i    a6, a3, 8
+    l32i    a7, a3, 12
+    l32i    a8, a3, 16
+    l32i    a9, a3, 20
+    l32i    a10, a3, 24
+    l32i    a11, a3, 28                                /* ensure PS and EPC written */
+    l32i    a12, a3, 32
+    l32i    a13, a3, 36
+    l32i    a14, a3, 40
+    l32i    a15, a3, 44
+
+    /* Done with the loop? */
+    beqz    a1, 2f
+    /* If no, rotate the window and repeat */
+    rotw    -3
+    j       1b
+
+2:
+    /* Done with the loop. Only 4 registers (a0-a3 in the original window) remain
+     * to be restored. Also need to restore WINDOWSTART, since all the general
+     * registers are now in place.
+     */
+    movi    a0, _rmt_save_ctx
+
+    l32i    a2, a0, SPECREG_OFFSET + 4
+    wsr     a2, WINDOWSTART
+
+    l32i    a1, a0, 4
+    l32i    a2, a0, 8
+    l32i    a3, a0, 12
+    rsr     a0, EXCSAVE_X  /* holds the value of a0 before the interrupt handler */
+
+    /* Return from the interrupt, restoring PS from EPS_X */
+    rfi     RFI_X
+
+
+/* The linker has no reason to link in this file; all symbols it exports are already defined
+   (weakly!) in the default int handler. Define a symbol here so we can use it to have the
+   linker inspect this anyway. */
+
+    .global ld_include_hli_vectors_rmt
+ld_include_hli_vectors_rmt:
+
+
+#endif // CONFIG_BTDM_CTRL_HLI
+#endif // WLEDMM
+#endif // XTensa