better handling of backbuffers

Author: Vincent-FK

drivers/staging/fbtft/fbtft-bus.c

@@ -146,16 +146,27 @@ int fbtft_start_new_screen_transfer_async(struct fbtft_par *par)
 				 "Display update%s: fps=%ld\n", 
 				 par->pdata->te_irq_enabled?" (TE)":"",
 				 par->avg_fps / par->nb_fps_values);
-			printk("Display update%s: fps=%ld, par->must_render=%d\n", 
+			printk("Display update%s: fps=%ld, par->nb_backbuffers_full=%d\n", 
 				 par->pdata->te_irq_enabled?" (TE)":"",
-				 par->avg_fps / par->nb_fps_values, par->must_render);
+				 par->avg_fps / par->nb_fps_values, par->nb_backbuffers_full);
 			par->avg_fps = 0;
 			par->nb_fps_values = 0;
 		}
 	}
 
 #endif //FPS_DEBUG
 
+	/* Get last memory buffer not written */
+	if(par->nb_backbuffers_full > 0){
+		par->vmem_ptr = par->vmem_back_buffers[par->vmem_prev_buf_idx];
+		par->nb_backbuffers_full--;
+		par->nb_backbuffers_full = !!par->nb_backbuffers_full; //back to 1 or 0 to avoid overflows
+	}
+	else{
+		par->nb_backbuffers_full = 0; // Avoid overflows, should not happen
+		par->vmem_ptr = par->info->screen_buffer;
+	}
+
 	/* Post process screen for doufle buf copy, notifs, rotation soft... */
 	fbtft_post_process_screen(par);
 

drivers/staging/fbtft/fbtft-core.c

@@ -578,13 +578,6 @@ void fbtft_post_process_screen(struct fbtft_par *par)
 		screen_post_process = true;
 	}
 
-	/* Get last memory buffer not written */
-	if(par->must_render){
-		par->vmem_ptr = par->vmem_back_buffers[par->vmem_prev_buf_idx];
-	}
-	else{
-		par->vmem_ptr = par->info->screen_buffer;
-	}
 	//par->vmem_ptr = par->vmem_back_buffers[par->vmem_prev_buf_idx];
 	//par->vmem_ptr = par->info->screen_buffer;
 
@@ -652,7 +645,7 @@ void fbtft_flip_backbuffer(struct fbtft_par *par)
 		par->vmem_size);
 	par->vmem_prev_buf_idx = par->vmem_cur_buf_idx;
 	par->vmem_cur_buf_idx = (par->vmem_cur_buf_idx+1)%FBTFT_VMEM_BUFS;
-	par->must_render++;
+	par->nb_backbuffers_full++;
 	//spin_unlock(&par->dirty_lock);
 }
 
@@ -1224,7 +1217,7 @@ struct fb_info *fbtft_framebuffer_alloc(struct fbtft_display *display,
 	par->vmem_prev_buf_idx = 0;
 	par->vmem_cur_buf_idx = 0;
 	par->vmem_ptr = par->info->screen_buffer + (par->vmem_cur_buf_idx*par->vmem_size);
-	par->must_render = 0;
+	par->nb_backbuffers_full = 0;
 	par->pdata = pdata;
 	pdata->par = par;
 	par->debug = display->debug;
@@ -1717,17 +1710,17 @@ static irqreturn_t irq_TE_handler(int irq_no, void *dev_id)
 		return IRQ_HANDLED;
 
 #if 0
-	if (pdata->par->must_render <= 0)
+	if (pdata->par->nb_backbuffers_full <= 0)
 		return IRQ_HANDLED;
 	/*static int prev_must_render = 0;
-	if (prev_must_render == pdata->par->must_render);
+	if (prev_must_render == pdata->par->nb_backbuffers_full);
 		return IRQ_HANDLED;*/
 
-	pdata->par->must_render--;
-	if(pdata->par->must_render > 1024){
-		pdata->par->must_render=1;
+	pdata->par->nb_backbuffers_full--;
+	if(pdata->par->nb_backbuffers_full > 1024){
+		pdata->par->nb_backbuffers_full=1;
 	}
-	prev_must_render = pdata->par->must_render;
+	prev_must_render = pdata->par->nb_backbuffers_full;
 #endif
 
 	fbtft_start_new_screen_transfer_async(pdata->par);

include/linux/fbtft.h

@@ -230,7 +230,7 @@ struct fbtft_par {
 	u8 vmem_prev_buf_idx;
 	u8 vmem_cur_buf_idx;
 	int vmem_size;
-	int must_render;
+	int nb_backbuffers_full;
 	u8 startbyte;
 	struct fbtft_ops fbtftops;
 	spinlock_t dirty_lock;