1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
Index: firmware/target/arm/ipod/lcd-as-color-nano.S
===================================================================
--- firmware/target/arm/ipod/lcd-as-color-nano.S  (revision 28934)
+++ firmware/target/arm/ipod/lcd-as-color-nano.S  (working copy)
@@ -24,129 +24,245 @@
 #include "config.h"
 #include "cpu.h"

-    .section    .icode, "ax", %progbits
+/**************************************************************************** 
+ * #define FORCE_FIFO_WAIT
+ *
+ * This is not needed in YUV blitting when the LCD IF is fast enough. In this
+ * case YUV-to-RGB conversion per pixel needs longer than the transfer of a 
+ * pixel via the LCD IF. For iPod nano 2G this is true if the LCD IF is 
+ * configured to use LCD_PHTIME = 0x00 (see lcd-nano2g.c).
+ ****************************************************************************/

+#include "config.h"
+
+#define FORCE_FIFO_WAIT
+
+    .section .icode, "ax", %progbits
+    
 /****************************************************************************
-*  void lcd_yuv_write_inner_loop(unsigned char const * const ysrc,
-*                                unsigned char const * const usrc,
-*                                unsigned char const * const vsrc,
-*                                int width);
-*
-*   YUV- > RGB565 conversion
-*   |R|   |1.000000 -0.000001  1.402000| |Y'|
-*   |G| = |1.000000 -0.334136 -0.714136| |Pb|
-*   |B|   |1.000000  1.772000  0.000000| |Pr|
-*   Scaled, normalized, rounded and tweaked to yield RGB 565:
-*   |R|   |74   0 101| |Y' -  16| >> 9
-*   |G| = |74 -24 -51| |Cb - 128| >> 8
-*   |B|   |74 128   0| |Cr - 128| >> 9
-*
-*/
+ * extern void lcd_write_yuv420_lines(unsigned char const * const src[3],
+ *                                    const unsigned LCD_BASE,
+ *                                    int width,
+ *                                    int stride);
+ *
+ *   Conversion from Motion JPEG and MPEG Y'PbPr to RGB is:
+ *   |R|   |1.164  0.000  1.596| |Y' -  16|
+ *   |G| = |1.164 -0.391 -0.813| |Pb - 128|
+ *   |B|   |1.164  2.018  0.000| |Pr - 128|
+ *
+ *   Scaled, normalized, rounded and tweaked to yield RGB 565:
+ *   |R|   |74   0 101| |Y' -  16| >> 9
+ *   |G| = |74 -24 -51| |Cb - 128| >> 8
+ *   |B|   |74 128   0| |Cr - 128| >> 9
+ *
+ * Converts two lines from YUV to RGB565 and writes to LCD at once. First loop
+ * loads Cb/Cr, calculates the chroma offset and saves them to buffer. Within
+ * the second loop these chroma offset are reloaded from buffer. Within each 
+ * loop two pixels are calculated and written to LCD. 
+ */
     .align      2
-    .global     lcd_yuv_write_inner_loop
-    .type       lcd_yuv_write_inner_loop, %function
+    .global     lcd_write_yuv420_lines
+    .type       lcd_write_yuv420_lines, %function
+lcd_write_yuv420_lines:
+                                      /* r0 = src = yuv_src */
+                                      /* r1 = dst = LCD_BASE */
+                                      /* r2 = width */
+                                      /* r3 = stride */                
+    stmfd       sp!, { r4-r10, lr }   /* save non-scratch */
+    ldmia       r0, { r9, r10, r12 }  /* r9 = yuv_src[0] = Y'_p */
+                                      /* r10 = yuv_src[1] = Cb_p */
+                                      /* r12 = yuv_src[2] = Cr_p */
+    add         r3, r9, r3            /* r3 = &ysrc[stride] */
+    add         r4, r2, r2, asr #1    /* chroma buffer lenght = width/2 *3 */
+    mov         r4, r4, asl #2        /*   use words for str/ldm possibility */
+    add         r4, r4, #19           /*   plus room for 4 additional words, */
+    bic         r4, r4, #3            /*   rounded up to multiples of 4 byte */
+    sub         sp, sp, r4            /*   and allocate on stack */
+    stmia       sp, {r1-r4}           /* LCD_BASE, width, &ysrc[stride], stack_alloc */

-lcd_yuv_write_inner_loop:
-                                        @ r0 = ysrc
-                                        @ r1 = usrc
-                                        @ r2 = vsrc
-                                        @ r3 = width
-    stmfd sp!, { r4-r11, lr }           @ save regs
-    mov r4, #0x70000000                 @ r4 = LCD2_BLOCK_CTRL - 0x20
-    add r4, r4, #0x8a00                 @
-    add r5, r4, #0x100                  @ r5 = LCD2_BLOCK_DATA
-10:                                     @ loop
+    mov         r7, r2                /* r7 = loop count */
+    add         r8, sp, #16           /* chroma buffer */
+    add         lr, r1, #0x100        /* LCD data port = LCD_BASE + 0x100 */

-    ldrb r7, [r1], #1                   @ *usrc++
-    ldrb r8, [r2], #1                   @ *vsrc++
+    /* 1st loop start */
+10:                                   /* loop start */

-    sub r7, r7, #128                    @ Cb -= 128
-    sub r8, r8, #128                    @ Cr -= 128
+    ldrb        r0, [r10], #1         /* r0 = *usrc++ = *Cb_p++ */
+    ldrb        r1, [r12], #1         /* r1 = *vsrc++ = *Cr_p++ */

-    add r10, r8, r8, asl #2             @ Cr*101
-    add r10, r10, r8, asl #5
-    add r10, r10, r8, asl #6
+    sub         r0, r0, #128          /* r0 = Cb-128 */
+    sub         r1, r1, #128          /* r1 = Cr-128 */

-    add r11, r8, r8, asl #1             @ Cr*51 + Cb*24
-    add r11, r11, r11, asl #4
-    add r11, r11, r7, asl #3
-    add r11, r11, r7, asl #4
+    add         r2, r1, r1, asl #1    /* r2 = Cr*51 + Cb*24 */
+    add         r2, r2, r2, asl #4   
+    add         r2, r2, r0, asl #3   
+    add         r2, r2, r0, asl #4   

-    add r12, r7, #2                     @ r12 = bu = (Cb*128 + 256) >> 9
-    mov r12, r12, asr #2
-    add r10, r10, #256                  @ r10 = rv = (Cr*101 + 256) >> 9
-    mov r10, r10, asr #9
-    rsb r11, r11, #128                  @ r11 = guv = (-r11 + 128) >> 8
-    mov r11, r11, asr #8
+    add         r4, r1, r1, asl #2    /* r1 = Cr*101 */
+    add         r4, r4, r1, asl #5
+    add         r1, r4, r1, asl #6

-@ pixel_1
-    ldrb r7, [r0], #1                   @ *ysrc++
-    sub r7, r7, #16                     @ Y = (Y' - 16) * 37
-    add r8, r7, r7, asl #2
-    add r7, r8, r7, asl #5
+    add         r1, r1, #256          /* r1 = rv = (r1 + 256) >> 9 */
+    mov         r1, r1, asr #9
+    rsb         r2, r2, #128          /* r2 = guv = (-r2 + 128) >> 8 */
+    mov         r2, r2, asr #8       
+    add         r0, r0, #2            /* r0 = bu = (Cb*128 + 256) >> 9 */
+    mov         r0, r0, asr #2       
+    stmia       r8!, {r0-r2}          /* store r0, r1 and r2 to chroma buffer */

-    add r9, r10, r7, asr #8             @ R = (Y >> 8) + rv
-    add r8, r11, r7, asr #7             @ G = (Y >> 7) + guv
-    add r7, r12, r7, asr #8             @ B = (Y >> 8) + bu
+    /* 1st loop, first pixel */
+    ldrb        r5, [r9], #1          /* r5 = *ysrc++ = *Y'_p++ */
+    sub         r5, r5, #16           /* r5 = (Y'-16) * 74 */
+    add         r3, r5, r5, asl #2
+    add         r5, r3, r5, asl #5

-    cmp r9, #31                         @ clamp R
-    mvnhi r9, r9, asr #31
-    andhi r9, r9, #31
+    add         r6, r1, r5, asr #8    /* r6 = r = (Y >> 9) + rv */
+    add         r3, r2, r5, asr #7    /* r3 = g = (Y >> 8) + guv */
+    add         r4, r0, r5, asr #8    /* r4 = b = (Y >> 9) + bu */

-    cmp r8, #63                         @ clamp G
-    mvnhi r8, r8, asr #31
-    andhi r8, r8, #63
+    orr         r5, r6, r4            /* check if clamping is needed... */
+    orr         r5, r5, r3, asr #1    /* ...at all */
+    cmp         r5, #31                 
+    bls         15f                   /* -> no clamp */
+    cmp         r6, #31               /* clamp r */
+    mvnhi       r6, r6, asr #31         
+    andhi       r6, r6, #31             
+    cmp         r3, #63               /* clamp g */
+    mvnhi       r3, r3, asr #31
+    andhi       r3, r3, #63
+    cmp         r4, #31               /* clamp b */
+    mvnhi       r4, r4, asr #31         
+    andhi       r4, r4, #31          
+15:                                   /* no clamp */

-    cmp r7, #31                         @ clamp B
-    mvnhi r7, r7, asr #31
-    andhi r7, r7, #31
+    /* calculate pixel_1 and save to r4 for later pixel packing */
+    orr         r4, r4, r3, lsl #5    /* pixel_1 = r<<11 | g<<5 | b */
+    orr         r4, r4, r6, lsl #11   /* r4 = pixel_1 */

-    orr r6, r7, r8, lsl #5              @ pack pixel
-    orr r6, r6, r9, lsl #11
+    /* 1st loop, second pixel */
+    ldrb        r5, [r9], #1          /* r5 = *ysrc++ = *Y'_p++ */
+    sub         r5, r5, #16           /* r5 = (Y'-16) * 74 */
+    add         r3, r5, r5, asl #2
+    add         r5, r3, r5, asl #5

-    mov r7, r6, lsl #8                  @ swap bytes
-    and r7, r7, #0xff00
-    add r6, r7, r6, lsr #8
+    add         r6, r1, r5, asr #8    /* r6 = r = (Y >> 9) + rv */
+    add         r3, r2, r5, asr #7    /* r3 = g = (Y >> 8) + guv */
+    add         r5, r0, r5, asr #8    /* r5 = b = (Y >> 9) + bu */   

-@ pixel_2
-    ldrb r7, [r0], #1                   @ *ysrc++
-    sub r7, r7, #16                     @ Y = (Y' - 16) * 37
-    add r8, r7, r7, asl #2
-    add r7, r8, r7, asl #5
+    orr         r0, r6, r5            /* check if clamping is needed... */
+    orr         r0, r0, r3, asr #1    /* ...at all */
+    cmp         r0, #31                 
+    bls         15f                   /* -> no clamp */
+    cmp         r6, #31               /* clamp r */
+    mvnhi       r6, r6, asr #31         
+    andhi       r6, r6, #31             
+    cmp         r3, #63               /* clamp g */
+    mvnhi       r3, r3, asr #31
+    andhi       r3, r3, #63
+    cmp         r5, #31               /* clamp b */
+    mvnhi       r5, r5, asr #31         
+    andhi       r5, r5, #31          
+15:                                   /* no clamp */

-    add r9, r10, r7, asr #8             @ R = (Y >> 8) + rv
-    add r8, r11, r7, asr #7             @ G = (Y >> 7) + guv
-    add r7, r12, r7, asr #8             @ B = (Y >> 8) + bu
+    /* calculate pixel_2 and pack with pixel_1 before writing */
+    orr         r5, r5, r3, lsl #5    /* pixel_2 = r<<11 | g<<5 | b */
+    orr         r5, r5, r6, lsl #11   /* r5 = pixel_2 */
+#ifdef FORCE_FIFO_WAIT
+    /* wait for FIFO half full */
+.fifo_wait1:
+    ldr         r3, [lr, #-0xE0]       /* while !(LCD2_BLOCK_CTRL & 0x1000000); */
+    tst         r3, #0x1000000
+    beq         .fifo_wait1
+#endif
+    stmia       lr, {r4,r5}           /* write pixel_1 and pixel_2 */

-    cmp r9, #31                         @ clamp R
-    mvnhi r9, r9, asr #31
-    andhi r9, r9, #31
+    subs        r7, r7, #2            /* check for loop end */
+    bgt         10b                   /* back to beginning  */
+    /* 1st loop end */

-    cmp r8, #63                         @ clamp G
-    mvnhi r8, r8, asr #31
-    andhi r8, r8, #63
+    /* Reload several registers for pointer rewinding for next loop */
+    add         r8, sp, #16           /* chroma buffer */
+    ldmia       sp, { r1, r7, r9}     /* r1  = LCD_BASE */
+                                      /* r7  = loop count */
+                                      /* r9 = &ysrc[stride] */   

-    cmp r7, #31                         @ clamp B
-    mvnhi r7, r7, asr #31
-    andhi r7, r7, #31
+    /* 2nd loop start */
+20:                                   /* loop start */
+    /* restore r0 (bu), r1 (rv) and r2 (guv) from chroma buffer */
+    ldmia       r8!, {r0-r2}

-    orr r7, r7, r8, lsl #5              @ pack pixel
-    orr r7, r7, r9, lsl #11
+    /* 2nd loop, first pixel */
+    ldrb        r5, [r9], #1          /* r5 = *ysrc++ = *Y'_p++ */
+    sub         r5, r5, #16           /* r5 = (Y'-16) * 74 */
+    add         r3, r5, r5, asl #2
+    add         r5, r3, r5, asl #5

-    orr r6, r6, r7, lsl #24             @ swap bytes and add pixels simultaneously
-    mov r7, r7, lsr #8
-    orr r6, r6, r7, lsl #16
-#if 1
-11:                                     @ while (!(LCD2_BLOCK_CTRL & LCD2_BLOCK_TXOK));
-    ldr r11, [r4, #0x20]                @
-    tst r11, #0x1000000                 @
-    beq 11b                             @
+    add         r6, r1, r5, asr #8    /* r6 = r = (Y >> 9) + rv */
+    add         r3, r2, r5, asr #7    /* r3 = g = (Y >> 8) + guv */
+    add         r4, r0, r5, asr #8    /* r4 = b = (Y >> 9) + bu */
+
+    orr         r5, r6, r4            /* check if clamping is needed... */
+    orr         r5, r5, r3, asr #1    /* ...at all */
+    cmp         r5, #31                 
+    bls         15f                   /* -> no clamp */
+    cmp         r6, #31               /* clamp r */
+    mvnhi       r6, r6, asr #31         
+    andhi       r6, r6, #31             
+    cmp         r3, #63               /* clamp g */
+    mvnhi       r3, r3, asr #31
+    andhi       r3, r3, #63
+    cmp         r4, #31               /* clamp b */
+    mvnhi       r4, r4, asr #31         
+    andhi       r4, r4, #31          
+15:                                   /* no clamp */
+    /* calculate pixel_1 and save to r4 for later pixel packing */
+    orr         r4, r4, r3, lsl #5    /* pixel_1 = r<<11 | g<<5 | b */
+    orr         r4, r4, r6, lsl #11   /* r4 = pixel_1 */
+
+    /* 2nd loop, second pixel */
+    ldrb        r5, [r9], #1          /* r5 = *ysrc++ = *Y'_p++ */
+    sub         r5, r5, #16           /* r5 = (Y'-16) * 74 */
+    add         r3, r5, r5, asl #2
+    add         r5, r3, r5, asl #5
+
+    add         r6, r1, r5, asr #8    /* r6 = r = (Y >> 9) + rv */
+    add         r3, r2, r5, asr #7    /* r3 = g = (Y >> 8) + guv */
+    add         r5, r0, r5, asr #8    /* r5 = b = (Y >> 9) + bu */
+
+    orr         r0, r6, r5            /* check if clamping is needed... */
+    orr         r0, r0, r3, asr #1    /* ...at all */
+    cmp         r0, #31                 
+    bls         15f                   /* -> no clamp */
+    cmp         r6, #31               /* clamp r */
+    mvnhi       r6, r6, asr #31         
+    andhi       r6, r6, #31             
+    cmp         r3, #63               /* clamp g */
+    mvnhi       r3, r3, asr #31
+    andhi       r3, r3, #63
+    cmp         r5, #31               /* clamp b */
+    mvnhi       r5, r5, asr #31         
+    andhi       r5, r5, #31          
+15:                                   /* no clamp */
+
+    /* calculate pixel_2 and pack with pixel_1 before writing */
+    orr         r5, r5, r3, lsl #5    /* pixel_2 = r<<11 | g<<5 | b */
+    orr         r5, r5, r6, lsl #11   /* r5 = pixel_2 */
+#ifdef FORCE_FIFO_WAIT
+    /* wait for FIFO half full */
+.fifo_wait2:
+    ldr         r3, [lr, #-0xE0]      /* while !(LCD2_BLOCK_CTRL & 0x1000000); */
+    tst         r3, #0x1000000
+    beq         .fifo_wait2
 #endif
-    str r6, [r5]                        @ send two pixels
+    stmia       lr, {r4,r5}           /* write pixel_1 and pixel_2 */

-    subs r3, r3, #2                     @ decrease width
-    bgt 10b                             @ loop
+    subs        r7, r7, #2            /* check for loop end */
+    bgt         20b                   /* back to beginning  */
+    /* 2nd loop end */

-    ldmpc regs=r4-r11                   @ restore regs
-    .ltorg                              @ dump constant pool
-    .size   lcd_yuv_write_inner_loop, .-lcd_yuv_write_inner_loop
+    ldr         r3, [sp, #12]
+    add         sp, sp, r3            /* deallocate buffer */
+    ldmpc       regs=r4-r10           /* restore registers */
+
+    .ltorg
+    .size   lcd_write_yuv420_lines, .-lcd_write_yuv420_lines
Index: firmware/target/arm/ipod/lcd-color_nano.c
===================================================================
--- firmware/target/arm/ipod/lcd-color_nano.c  (revision 28932)
+++ firmware/target/arm/ipod/lcd-color_nano.c  (working copy)
@@ -120,22 +120,20 @@
 #endif
 }

-/*** update functions ***/
-extern void lcd_yuv_write_inner_loop(unsigned char const * const ysrc,
-                                     unsigned char const * const usrc,
-                                     unsigned char const * const vsrc,
-                                     int width);
+/* Line write helper function for lcd_yuv_blit. Writes two lines of yuv420. */
+extern void lcd_write_yuv420_lines(unsigned char const * const src[3],
+                                   const unsigned int lcd_baseadress,
+                                   int width,
+                                   int stride);

-#define CSUB_X 2
-#define CSUB_Y 2
-
 /* Performance function to blit a YUV bitmap directly to the LCD */
 void lcd_blit_yuv(unsigned char * const src[3],
                   int src_x, int src_y, int stride,
                   int x, int y, int width, int height)
 {
     int h;
-    int y0, x0, y1, x1;
+    int z, y0, x0, y1, x1;
+    unsigned char const * yuv_src[3];

     width = (width + 1) & ~1;

@@ -195,24 +193,18 @@
         LCD2_PORT = (LCD2_CMD_MASK|LCD_CNTL_WRITE_TO_GRAM);
     }

-    const int stride_div_csub_x = stride/CSUB_X;
+    z = stride * src_y;
+    yuv_src[0] = src[0] + z + src_x;
+    yuv_src[1] = src[1] + (z >> 2) + (src_x >> 1);
+    yuv_src[2] = src[2] + (yuv_src[1] - src[1]);

-    h=0;
-    while (1)
-    {
-        /* upsampling, YUV->RGB conversion and reduction to RGB565 in one go */
-        const unsigned char *ysrc = src[0] + stride * src_y + src_x;
+    height >>= 1;

-        const int uvoffset = stride_div_csub_x * (src_y/CSUB_Y) +
-                             (src_x/CSUB_X);
-
-        const unsigned char *usrc = src[1] + uvoffset;
-        const unsigned char *vsrc = src[2] + uvoffset;
-
+    h=0;
+    while (1) {
         int pixels_to_write;

-        if (h==0)
-        {
+        if (h==0) {
             while (!(LCD2_BLOCK_CTRL & LCD2_BLOCK_READY));
             LCD2_BLOCK_CONFIG = 0;

@@ -221,9 +213,7 @@
             pixels_to_write = (width * height) * 2;
             h = height;

-            /* calculate how much we can do in one go */
-            if (pixels_to_write > 0x10000)
-            {
+            if (pixels_to_write > 0x10000) {
                 h = (0x10000/2) / width;
                 pixels_to_write = (width * h) * 2;
             }
@@ -234,9 +224,11 @@
             LCD2_BLOCK_CTRL = 0x34000000;
         }

-        lcd_yuv_write_inner_loop(ysrc,usrc,vsrc,width);
+        lcd_write_yuv420_lines(yuv_src, LCD2_BASE, width, stride);
+        yuv_src[0] += stride << 1;
+        yuv_src[1] += stride >> 1; /* Skip down one chroma line */
+        yuv_src[2] += stride >> 1;

-        src_y++;
         h--;
     }