Add flash-access code (disabled because WIP)

software/libdvi/dvi.c

@@ -23,6 +23,7 @@ static void dvi_dma0_irq();
 static void dvi_dma1_irq();
 
 void dvi_init(struct dvi_inst *inst, uint spinlock_tmds_queue, uint spinlock_colour_queue) {
+	inst->started = inst->suspendflag = false;
 	dvi_timing_state_init(&inst->timing_state);
 	dvi_serialiser_init(&inst->ser_cfg);
 	for (int i = 0; i < N_TMDS_LANES; ++i) {
@@ -82,6 +83,25 @@ void dvi_register_irqs_this_core(struct dvi_inst *inst, uint irq_num) {
 	irq_set_enabled(irq_num, true);
 }
 
+// Start/stop code from mlorenzatiglb on github:
+// https://github.com/mlorenzati/PicoDVI
+void dvi_unregister_irqs_this_core(struct dvi_inst *inst, uint irq_num) {
+	irq_set_enabled(irq_num, false);
+	if (irq_num == DMA_IRQ_0) {
+		irq_remove_handler(DMA_IRQ_0, dvi_dma0_irq);
+	} else {
+		irq_remove_handler(DMA_IRQ_1, dvi_dma1_irq);
+	}
+	if (inst->tmds_buf_release) {
+		queue_try_add_u32(&inst->q_tmds_free, &inst->tmds_buf_release);
+	}
+	if (inst->tmds_buf_release_next) {
+		queue_try_add_u32(&inst->q_tmds_free, &inst->tmds_buf_release_next);
+	}
+	inst->tmds_buf_release = NULL;
+	inst->tmds_buf_release_next = NULL;
+}
+
 // Set up control channels to make transfers to data channels' control
 // registers (but don't trigger the control channels -- this is done either by
 // data channel CHAIN_TO or an initial write to MULTI_CHAN_TRIGGER)
@@ -107,6 +127,11 @@ static inline void __attribute__((always_inline)) _dvi_load_dma_op(const struct
 // CHAIN_TO on data channel completion. IRQ handler *must* be prepared before
 // calling this. (Hooked to DMA IRQ0)
 void dvi_start(struct dvi_inst *inst) {
+	if (inst->started) return;
+	// Purge any FIFO cruft that dvi_stop() may have left
+	for (int i = 0; i < N_TMDS_LANES; ++i) {
+		pio_sm_clear_fifos(inst->ser_cfg.pio, inst->ser_cfg.sm_tmds[i]);
+	}
 	_dvi_load_dma_op(inst->dma_cfg, &inst->dma_list_vblank_nosync);
 	dma_start_channel_mask(
 		(1u << inst->dma_cfg[0].chan_ctrl) |
@@ -115,14 +140,38 @@ void dvi_start(struct dvi_inst *inst) {
 
 	// We really don't want the FIFOs to bottom out, so wait for full before
 	// starting the shift-out.
-	for (int i = 0; i < N_TMDS_LANES; ++i)
+	for (int i = 0; i < N_TMDS_LANES; ++i) {
 		while (!pio_sm_is_tx_fifo_full(inst->ser_cfg.pio, inst->ser_cfg.sm_tmds[i]))
 			tight_loop_contents();
+	}
 	dvi_serialiser_enable(&inst->ser_cfg, true);
+	inst->started = true;
+}
+
+// Start/stop code from mlorenzatiglb on github:
+// https://github.com/mlorenzati/PicoDVI
+void dvi_stop(struct dvi_inst *inst) {
+	if (!inst->started) return;
+	uint mask  = 0;
+	for (int i = 0; i < N_TMDS_LANES; ++i) {
+		dma_channel_config cfg = dma_channel_get_default_config(inst->dma_cfg[i].chan_ctrl);
+		dma_channel_set_config(inst->dma_cfg[i].chan_ctrl, &cfg, false);
+		cfg = dma_channel_get_default_config(inst->dma_cfg[i].chan_data);
+		dma_channel_set_config(inst->dma_cfg[i].chan_data, &cfg, false);
+		mask |= 1 << inst->dma_cfg[i].chan_data;
+		mask |= 1 << inst->dma_cfg[i].chan_ctrl;
+	}
+
+	dma_channel_abort(mask);
+	dma_irqn_acknowledge_channel(0, inst->dma_cfg[TMDS_SYNC_LANE].chan_data);
+	dma_hw->ints0 = 1u << inst->dma_cfg[TMDS_SYNC_LANE].chan_data;
+
+	dvi_serialiser_enable(&inst->ser_cfg, false);
+	inst->started = false;
 }
 
 static inline void __dvi_func_x(_dvi_prepare_scanline_8bpp)(struct dvi_inst *inst, uint32_t *scanbuf) {
-	uint32_t *tmdsbuf;
+	uint32_t *tmdsbuf = NULL;
 	queue_remove_blocking_u32(&inst->q_tmds_free, &tmdsbuf);
 	uint pixwidth = inst->timing->h_active_pixels;
 	uint words_per_channel = pixwidth / DVI_SYMBOLS_PER_WORD;
@@ -134,7 +183,7 @@ static inline void __dvi_func_x(_dvi_prepare_scanline_8bpp)(struct dvi_inst *ins
 }
 
 static inline void __dvi_func_x(_dvi_prepare_scanline_16bpp)(struct dvi_inst *inst, uint32_t *scanbuf) {
-	uint32_t *tmdsbuf;
+	uint32_t *tmdsbuf = NULL;
 	queue_remove_blocking_u32(&inst->q_tmds_free, &tmdsbuf);
 	uint pixwidth = inst->timing->h_active_pixels;
 	uint words_per_channel = pixwidth / DVI_SYMBOLS_PER_WORD;
@@ -150,7 +199,17 @@ static inline void __dvi_func_x(_dvi_prepare_scanline_16bpp)(struct dvi_inst *in
 void __dvi_func(dvi_scanbuf_main_8bpp)(struct dvi_inst *inst) {
 	uint y = 0;
 	while (1) {
-		uint32_t *scanbuf;
+		if (inst->suspendflag) {
+			dvi_unregister_irqs_this_core(inst, DMA_IRQ_0);
+			dvi_stop(inst);
+			inst->suspendflag = false;  // Ack core 0
+			while (!inst->suspendflag); // Wait for restart
+			//y = 0;
+			dvi_register_irqs_this_core(inst, DMA_IRQ_0);
+			dvi_start(inst);
+			inst->suspendflag = false;  // Ack core 0
+		}
+		uint32_t *scanbuf = NULL;
 		queue_remove_blocking_u32(&inst->q_colour_valid, &scanbuf);
 		_dvi_prepare_scanline_8bpp(inst, scanbuf);
 		queue_add_blocking_u32(&inst->q_colour_free, &scanbuf);
@@ -166,7 +225,17 @@ void __dvi_func(dvi_scanbuf_main_8bpp)(struct dvi_inst *inst) {
 void __dvi_func(dvi_scanbuf_main_16bpp)(struct dvi_inst *inst) {
 	uint y = 0;
 	while (1) {
-		uint32_t *scanbuf;
+		if (inst->suspendflag) {
+			dvi_unregister_irqs_this_core(inst, DMA_IRQ_0);
+			dvi_stop(inst);
+			inst->suspendflag = false;  // Ack core 0
+			while (!inst->suspendflag); // Wait for restart
+			//y = 0;
+			dvi_register_irqs_this_core(inst, DMA_IRQ_0);
+			dvi_start(inst);
+			inst->suspendflag = false;  // Ack core 0
+		}
+		uint32_t *scanbuf = NULL;
 		queue_remove_blocking_u32(&inst->q_colour_valid, &scanbuf);
 		_dvi_prepare_scanline_16bpp(inst, scanbuf);
 		queue_add_blocking_u32(&inst->q_colour_free, &scanbuf);
@@ -195,7 +264,7 @@ static void __dvi_func(dvi_dma_irq_handler)(struct dvi_inst *inst) {
 			tight_loop_contents();
 	}
 
-	uint32_t *tmdsbuf;
+	uint32_t *tmdsbuf = NULL;
 	while (inst->late_scanline_ctr > 0 && queue_try_remove_u32(&inst->q_tmds_valid, &tmdsbuf)) {
 		// If we displayed this buffer then it would be in the wrong vertical
 		// position on-screen. Just pass it back.

software/libdvi/dvi.h

@@ -46,6 +46,8 @@ struct dvi_inst {
 	queue_t q_colour_valid;
 	queue_t q_colour_free;
 
+	bool started;
+	volatile bool suspendflag;
 };
 
 #if defined(__cplusplus)
@@ -60,10 +62,16 @@ void dvi_init(struct dvi_inst *inst, uint spinlock_tmds_queue, uint spinlock_col
 // whichever core called this function. Registers an exclusive IRQ handler.
 void dvi_register_irqs_this_core(struct dvi_inst *inst, uint irq_num);
 
+// Unregisters DVI irq callbacks for this core
+void dvi_unregister_irqs_this_core(struct dvi_inst *inst, uint irq_num);
+
 // Start actually wiggling TMDS pairs. Call this once you have initialised the
 // DVI, have registered the IRQs, and are producing rendered scanlines.
 void dvi_start(struct dvi_inst *inst);
 
+// Stops DVI pairs generations
+void dvi_stop(struct dvi_inst *inst);
+
 // TMDS encode worker function: core enters and doesn't leave, but still
 // responds to IRQs. Repeatedly pop a scanline buffer from q_colour_valid,
 // TMDS encode it, and pass it to the tmds valid queue.

src/PicoDVI.cpp

@@ -39,18 +39,36 @@ static PicoDVI *dviptr = NULL; // For C access to active C++ object
   @brief  Runs on core 1 on startup; this is how Philhower RP2040 handles
           multiprocessing.
 */
-void setup1(void) {
+void __not_in_flash_func(setup1)(void) {
   while (dviptr == NULL) // Wait for PicoDVI::begin() to start on core 0
     yield();
   dviptr->_setup();
 }
 
 // Runs on core 1 after dviptr set
-void PicoDVI::_setup(void) {
+void __not_in_flash_func(PicoDVI::_setup)(void) {
   while (wait_begin)
     ; // Wait for DVIGFX*::begin() to set this
+
   dvi_register_irqs_this_core(&dvi0, DMA_IRQ_0);
   dvi_start(&dvi0);
+
+#if 0
+  // From CircuitPython source. Turns off flash access for core 1; any
+  // access will hard fault from here forward, but is better than messing
+  // up the CIRCUITPY filesystem.
+  MPU->CTRL = MPU_CTRL_PRIVDEFENA_Msk | MPU_CTRL_ENABLE_Msk;
+  MPU->RNR  = 6; // 7 is used by pico-sdk stack protection.
+  MPU->RBAR = XIP_MAIN_BASE | MPU_RBAR_VALID_Msk;
+  MPU->RASR = MPU_RASR_XN_Msk     |        // Execute never + restrict all else
+              MPU_RASR_ENABLE_Msk |
+              (0x1b << MPU_RASR_SIZE_Pos); // Mask up to SRAM region.
+  MPU->RNR = 7;
+  // Doesn't actually work yet though. Keeping this chunk of code around for
+  // notes, as getting all the vital functions in RAM may provide a simpler
+  // solution than the suspend/resume code as currently written.
+#endif
+
   (*mainloop)(&dvi0);
 }
 
@@ -251,6 +269,15 @@ static void mainloop1(struct dvi_inst *inst) {
 
 void __not_in_flash_func(DVIGFX1::_mainloop)(void) {
   for (;;) {
+    if (dvi0.suspendflag) {
+      dvi_unregister_irqs_this_core(&dvi0, DMA_IRQ_0);
+      dvi_stop(&dvi0);
+      dvi0.suspendflag = false;  // Ack core 0
+      while (!dvi0.suspendflag); // Wait for restart
+      dvi_register_irqs_this_core(&dvi0, DMA_IRQ_0);
+      dvi_start(&dvi0);
+      dvi0.suspendflag = false;  // Ack core 0
+    }
     uint8_t *b8 = buffer_save;
     if (dbuf)
       b8 += ((WIDTH + 7) / 8) * HEIGHT * (1 - back_index);
@@ -387,6 +414,15 @@ static void mainlooptext1(struct dvi_inst *inst) {
 
 void __not_in_flash_func(DVItext1::_mainloop)(void) {
   for (;;) {
+    if (dvi0.suspendflag) {
+      dvi_unregister_irqs_this_core(&dvi0, DMA_IRQ_0);
+      dvi_stop(&dvi0);
+      dvi0.suspendflag = false;  // Ack core 0
+      while (!dvi0.suspendflag); // Wait for restart
+      dvi_register_irqs_this_core(&dvi0, DMA_IRQ_0);
+      dvi_start(&dvi0);
+      dvi0.suspendflag = false;  // Ack core 0
+    }
     for (uint16_t y = 0; y < HEIGHT; y++) {
       uint16_t *row = getBuffer() + y * WIDTH;
       for (uint8_t y1 = 0; y1 < 8; y1++) {
@@ -429,3 +465,34 @@ bool DVItext1::begin(void) {
   }
   return false;
 }
+
+// Start/stop code from mlorenzatiglb on github:
+// https://github.com/mlorenzati/PicoDVI
+// This part just sets flags to communicate between cores;
+// the actual suspend/resume takes place over in libdvi.
+
+void PicoDVI::_toggle(void) {
+  // DVI start/stop must occur on core 1. Signal DVI main loop to toggle
+  // its state (suspend or resume), block until acknowledged.
+  for (dviptr->dvi0.suspendflag = true; dviptr->dvi0.suspendflag; );
+}
+
+/*!
+  @brief  Pause DVI output. This ability is required for code that writes
+          to flash memory (such as Adafruit_CPFS). It's declared outside
+          the PicoDVI class so that other code can declare a 'weak' version
+          that's referenced if not linking with the PicoDVI library; the
+          libraries need not be interdependent, but can still work together.
+*/
+void PicoDVI_suspend(void) {
+  if (dviptr) dviptr->_toggle();
+}
+
+/*!
+  @brief  Resume previously-paused DVI output. Declared outside the PicoDVI
+          class so that other code can declare a 'weak' version if not
+          linking with the PicoDVI library.
+*/
+void PicoDVI_resume(void) {
+  if (dviptr) dviptr->_toggle();
+}

src/PicoDVI.h

@@ -65,6 +65,12 @@ public:
             C init code to access protected elements.
   */
   void _setup(void);
+  /*!
+    @brief  Internal function for DVI suspend/resume. User code should not
+            touch this, but needed for C PicoDVI_suspend() & PicoDVI_resume()
+            functions.
+  */
+  void _toggle(void);
 
 protected:
   /*!
@@ -341,3 +347,6 @@ public:
 
 protected:
 };
+
+void PicoDVI_suspend(void);
+void PicoDVI_resume(void);

src/libdvi/dvi.c

@@ -23,6 +23,7 @@ static void dvi_dma0_irq();
 static void dvi_dma1_irq();
 
 void dvi_init(struct dvi_inst *inst, uint spinlock_tmds_queue, uint spinlock_colour_queue) {
+	inst->started = inst->suspendflag = false;
 	dvi_timing_state_init(&inst->timing_state);
 	dvi_serialiser_init(&inst->ser_cfg);
 	for (int i = 0; i < N_TMDS_LANES; ++i) {
@@ -82,6 +83,25 @@ void dvi_register_irqs_this_core(struct dvi_inst *inst, uint irq_num) {
 	irq_set_enabled(irq_num, true);
 }
 
+// Start/stop code from mlorenzatiglb on github:
+// https://github.com/mlorenzati/PicoDVI
+void dvi_unregister_irqs_this_core(struct dvi_inst *inst, uint irq_num) {
+	irq_set_enabled(irq_num, false);
+	if (irq_num == DMA_IRQ_0) {
+		irq_remove_handler(DMA_IRQ_0, dvi_dma0_irq);
+	} else {
+		irq_remove_handler(DMA_IRQ_1, dvi_dma1_irq);
+	}
+	if (inst->tmds_buf_release) {
+		queue_try_add_u32(&inst->q_tmds_free, &inst->tmds_buf_release);
+	}
+	if (inst->tmds_buf_release_next) {
+		queue_try_add_u32(&inst->q_tmds_free, &inst->tmds_buf_release_next);
+	}
+	inst->tmds_buf_release = NULL;
+	inst->tmds_buf_release_next = NULL;
+}
+
 // Set up control channels to make transfers to data channels' control
 // registers (but don't trigger the control channels -- this is done either by
 // data channel CHAIN_TO or an initial write to MULTI_CHAN_TRIGGER)
@@ -107,6 +127,11 @@ static inline void __attribute__((always_inline)) _dvi_load_dma_op(const struct
 // CHAIN_TO on data channel completion. IRQ handler *must* be prepared before
 // calling this. (Hooked to DMA IRQ0)
 void dvi_start(struct dvi_inst *inst) {
+	if (inst->started) return;
+	// Purge any FIFO cruft that dvi_stop() may have left
+	for (int i = 0; i < N_TMDS_LANES; ++i) {
+		pio_sm_clear_fifos(inst->ser_cfg.pio, inst->ser_cfg.sm_tmds[i]);
+	}
 	_dvi_load_dma_op(inst->dma_cfg, &inst->dma_list_vblank_nosync);
 	dma_start_channel_mask(
 		(1u << inst->dma_cfg[0].chan_ctrl) |
@@ -115,14 +140,38 @@ void dvi_start(struct dvi_inst *inst) {
 
 	// We really don't want the FIFOs to bottom out, so wait for full before
 	// starting the shift-out.
-	for (int i = 0; i < N_TMDS_LANES; ++i)
+	for (int i = 0; i < N_TMDS_LANES; ++i) {
 		while (!pio_sm_is_tx_fifo_full(inst->ser_cfg.pio, inst->ser_cfg.sm_tmds[i]))
 			tight_loop_contents();
+	}
 	dvi_serialiser_enable(&inst->ser_cfg, true);
+	inst->started = true;
+}
+
+// Start/stop code from mlorenzatiglb on github:
+// https://github.com/mlorenzati/PicoDVI
+void dvi_stop(struct dvi_inst *inst) {
+	if (!inst->started) return;
+	uint mask  = 0;
+	for (int i = 0; i < N_TMDS_LANES; ++i) {
+		dma_channel_config cfg = dma_channel_get_default_config(inst->dma_cfg[i].chan_ctrl);
+		dma_channel_set_config(inst->dma_cfg[i].chan_ctrl, &cfg, false);
+		cfg = dma_channel_get_default_config(inst->dma_cfg[i].chan_data);
+		dma_channel_set_config(inst->dma_cfg[i].chan_data, &cfg, false);
+		mask |= 1 << inst->dma_cfg[i].chan_data;
+		mask |= 1 << inst->dma_cfg[i].chan_ctrl;
+	}
+
+	dma_channel_abort(mask);
+	dma_irqn_acknowledge_channel(0, inst->dma_cfg[TMDS_SYNC_LANE].chan_data);
+	dma_hw->ints0 = 1u << inst->dma_cfg[TMDS_SYNC_LANE].chan_data;
+
+	dvi_serialiser_enable(&inst->ser_cfg, false);
+	inst->started = false;
 }
 
 static inline void __dvi_func_x(_dvi_prepare_scanline_8bpp)(struct dvi_inst *inst, uint32_t *scanbuf) {
-	uint32_t *tmdsbuf;
+	uint32_t *tmdsbuf = NULL;
 	queue_remove_blocking_u32(&inst->q_tmds_free, &tmdsbuf);
 	uint pixwidth = inst->timing->h_active_pixels;
 	uint words_per_channel = pixwidth / DVI_SYMBOLS_PER_WORD;
@@ -134,7 +183,7 @@ static inline void __dvi_func_x(_dvi_prepare_scanline_8bpp)(struct dvi_inst *ins
 }
 
 static inline void __dvi_func_x(_dvi_prepare_scanline_16bpp)(struct dvi_inst *inst, uint32_t *scanbuf) {
-	uint32_t *tmdsbuf;
+	uint32_t *tmdsbuf = NULL;
 	queue_remove_blocking_u32(&inst->q_tmds_free, &tmdsbuf);
 	uint pixwidth = inst->timing->h_active_pixels;
 	uint words_per_channel = pixwidth / DVI_SYMBOLS_PER_WORD;
@@ -150,7 +199,17 @@ static inline void __dvi_func_x(_dvi_prepare_scanline_16bpp)(struct dvi_inst *in
 void __dvi_func(dvi_scanbuf_main_8bpp)(struct dvi_inst *inst) {
 	uint y = 0;
 	while (1) {
-		uint32_t *scanbuf;
+		if (inst->suspendflag) {
+			dvi_unregister_irqs_this_core(inst, DMA_IRQ_0);
+			dvi_stop(inst);
+			inst->suspendflag = false;  // Ack core 0
+			while (!inst->suspendflag); // Wait for restart
+			//y = 0;
+			dvi_register_irqs_this_core(inst, DMA_IRQ_0);
+			dvi_start(inst);
+			inst->suspendflag = false;  // Ack core 0
+		}
+		uint32_t *scanbuf = NULL;
 		queue_remove_blocking_u32(&inst->q_colour_valid, &scanbuf);
 		_dvi_prepare_scanline_8bpp(inst, scanbuf);
 		queue_add_blocking_u32(&inst->q_colour_free, &scanbuf);
@@ -166,7 +225,17 @@ void __dvi_func(dvi_scanbuf_main_8bpp)(struct dvi_inst *inst) {
 void __dvi_func(dvi_scanbuf_main_16bpp)(struct dvi_inst *inst) {
 	uint y = 0;
 	while (1) {
-		uint32_t *scanbuf;
+		if (inst->suspendflag) {
+			dvi_unregister_irqs_this_core(inst, DMA_IRQ_0);
+			dvi_stop(inst);
+			inst->suspendflag = false;  // Ack core 0
+			while (!inst->suspendflag); // Wait for restart
+			//y = 0;
+			dvi_register_irqs_this_core(inst, DMA_IRQ_0);
+			dvi_start(inst);
+			inst->suspendflag = false;  // Ack core 0
+		}
+		uint32_t *scanbuf = NULL;
 		queue_remove_blocking_u32(&inst->q_colour_valid, &scanbuf);
 		_dvi_prepare_scanline_16bpp(inst, scanbuf);
 		queue_add_blocking_u32(&inst->q_colour_free, &scanbuf);
@@ -195,7 +264,7 @@ static void __dvi_func(dvi_dma_irq_handler)(struct dvi_inst *inst) {
 			tight_loop_contents();
 	}
 
-	uint32_t *tmdsbuf;
+	uint32_t *tmdsbuf = NULL;
 	while (inst->late_scanline_ctr > 0 && queue_try_remove_u32(&inst->q_tmds_valid, &tmdsbuf)) {
 		// If we displayed this buffer then it would be in the wrong vertical
 		// position on-screen. Just pass it back.

src/libdvi/dvi.h

@@ -46,6 +46,8 @@ struct dvi_inst {
 	queue_t q_colour_valid;
 	queue_t q_colour_free;
 
+	bool started;
+	volatile bool suspendflag;
 };
 
 #if defined(__cplusplus)
@@ -60,10 +62,16 @@ void dvi_init(struct dvi_inst *inst, uint spinlock_tmds_queue, uint spinlock_col
 // whichever core called this function. Registers an exclusive IRQ handler.
 void dvi_register_irqs_this_core(struct dvi_inst *inst, uint irq_num);
 
+// Unregisters DVI irq callbacks for this core
+void dvi_unregister_irqs_this_core(struct dvi_inst *inst, uint irq_num);
+
 // Start actually wiggling TMDS pairs. Call this once you have initialised the
 // DVI, have registered the IRQs, and are producing rendered scanlines.
 void dvi_start(struct dvi_inst *inst);
 
+// Stops DVI pairs generations
+void dvi_stop(struct dvi_inst *inst);
+
 // TMDS encode worker function: core enters and doesn't leave, but still
 // responds to IRQs. Repeatedly pop a scanline buffer from q_colour_valid,
 // TMDS encode it, and pass it to the tmds valid queue.