TI AM335x kernel 4.4.12 LCD display 時鐘翻轉記錄

因為公司硬件上已經確定LCD 轉LVDS 轉換芯片上確認以上升沿時鐘為基準，所以只能在軟件上調整相關東西。

入口在：

drivers/gpu/drm/tilcdc/tilcdc_drv.c入口函數： module_init(tilcdc_drm_init); 出口函數： module_exit(tilcdc_drm_fini); 722 static int __init tilcdc_drm_init(void) 723 { 724 DBG("init"); 725 tilcdc_tfp410_init(); 726 tilcdc_panel_init(); ---> 這里面有關監視器的初始化---------- 727 return platform_driver_register(&tilcdc_platform_driver); | 728 } | | | drivers/gpu/drm/tilcdc/tilcdc_panel.c || 452 int __init tilcdc_panel_init(void) <-------------------------- 453 { 454 return platform_driver_register(&panel_driver); 455 } |---------- | 437 static struct of_device_id panel_of_match[] = { | 438 { .compatible = "ti,tilcdc,panel", }, | 439 { }, | 440 }; | 441 | 442 struct platform_driver panel_driver = { <------------ 443 .probe = panel_probe, 444 .remove = panel_remove, 445 .driver = { 446 .owner = THIS_MODULE, 447 .name = "panel", 448 .of_match_table = panel_of_match, 449 }, 450 };

根據panel_of_match[].compatible = "ti,tilcdc,panel", 找到設備樹相應內容。 arch/arm/boot/dts/am335x-chenfl.dts47 panel {48 compatible = "ti,tilcdc,panel";49 status = "okay";50 pinctrl-names = "default";51 pinctrl-0 = <&lcd_pins_s0>;52 panel-info {53 ac-bias = <255>;54 ac-bias-intrpt = <0>;55 dma-burst-sz = <16>;56 bpp = <16>;57 fdd = <0x80>;58 sync-edge = <0>;59 sync-ctrl = <1>;60 raster-order = <0>;61 fifo-th = <0>;62 invert-pxl-clk = <1>;63 };64 65 display-timings {66 native-mode = <&timing0>;67 timing0: 800x480 {68 clock-frequency = <33260000>;69 hactive = <800>;70 vactive = <480>;71 hfront-porch = <39>;72 hback-porch = <39>;73 hsync-len = <47>;74 vback-porch = <29>;75 vfront-porch = <13>;76 vsync-len = <2>;77 hsync-active = <1>;78 vsync-active = <1>;79 };80 };81 };

確定平臺設備與平臺驅動已經相互匹配之后，我們可以直接跟蹤驅動的probe 回到drivers/gpu/drm/tilcdc/tilcdc_panel.c 看到：442 struct platform_driver panel_driver = { 443 .probe = panel_probe, 444 .remove = panel_remove, 445 .driver = { 446 .owner = THIS_MODULE, 447 .name = "panel", 448 .of_match_table = panel_of_match, 449 }, 450 }; panel_probe: 341 static int panel_probe(struct platform_device *pdev) 342 { 343 struct device_node *bl_node, *node = pdev->dev.of_node; 344 struct panel_module *panel_mod; 345 struct tilcdc_module *mod; 346 struct pinctrl *pinctrl; 347 int ret; 348 /* 如果沒有設備樹數據就直接跳出來 */ 349 /* bail out early if no DT data: */ 350 if (!node) { 351 dev_err(&pdev->dev, "device-tree data is missing\n"); 352 return -ENXIO; 353 } 354 355 panel_mod = devm_kzalloc(&pdev->dev, sizeof(*panel_mod), GFP_KERNEL); 356 if (!panel_mod) 357 return -ENOMEM; 358 359 bl_node = of_parse_phandle(node, "backlight", 0); 360 if (bl_node) { 361 panel_mod->backlight = of_find_backlight_by_node(bl_node); 362 of_node_put(bl_node); 363 364 if (!panel_mod->backlight) 365 return -EPROBE_DEFER; 366 367 dev_info(&pdev->dev, "found backlight\n"); 368 } 369 370 panel_mod->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable", 371 GPIOD_OUT_LOW); 372 if (IS_ERR(panel_mod->enable_gpio)) { 373 ret = PTR_ERR(panel_mod->enable_gpio); 374 dev_err(&pdev->dev, "failed to request enable GPIO\n"); 375 goto fail_backlight; 376 } 377 378 if (panel_mod->enable_gpio) 379 dev_info(&pdev->dev, "found enable GPIO\n"); 380 381 mod = &panel_mod->base; 382 pdev->dev.platform_data = mod; 383 384 tilcdc_module_init(mod, "panel", &panel_module_ops); 385 386 pinctrl = devm_pinctrl_get_select_default(&pdev->dev); 387 if (IS_ERR(pinctrl)) 388 dev_warn(&pdev->dev, "pins are not configured\n"); 389 /* 對應時序的設置，和設備樹中的display-timings 有關 */ 390 panel_mod->timings = of_get_display_timings(node); 391 if (!panel_mod->timings) { 392 dev_err(&pdev->dev, "could not get panel timings\n"); 393 ret = -EINVAL; 394 goto fail_free; 395 } 396 /* 對應的相關信息設置，跟panel-info 這個節點有關 */ 397 panel_mod->info = of_get_panel_info(node); 398 if (!panel_mod->info) { 399 dev_err(&pdev->dev, "could not get panel info\n"); 400 ret = -EINVAL; 401 goto fail_timings; 402 } 403 404 mod->preferred_bpp = panel_mod->info->bpp; 405 406 return 0; 407 408 fail_timings: 409 display_timings_release(panel_mod->timings); 410 411 fail_free: 412 tilcdc_module_cleanup(mod); 413 414 fail_backlight: 415 if (panel_mod->backlight) 416 put_device(&panel_mod->backlight->dev); 417 return ret; 418 } /* 這是上面的 of_get_panel_info 傳進來的 */ 292 static struct tilcdc_panel_info *of_get_panel_info(struct device_node *np) 293 { 294 struct device_node *info_np; 295 struct tilcdc_panel_info *info; 296 int ret = 0; 297 298 if (!np) { 299 pr_err("%s: no devicenode given\n", __func__); 300 return NULL; 301 } 302 303 info_np = of_get_child_by_name(np, "panel-info"); 304 if (!info_np) { 305 pr_err("%s: could not find panel-info node\n", __func__); 306 return NULL; 307 } 308 309 info = kzalloc(sizeof(*info), GFP_KERNEL); 310 if (!info) { 311 pr_err("%s: allocation failed\n", __func__); 312 of_node_put(info_np); 313 return NULL; 314 } 315 /* 這里我們可以看到，如果一個出錯，ret 就會為真，這是上面的設備樹的必需選項的配對 */ 316 ret |= of_property_read_u32(info_np, "ac-bias", &info->ac_bias); 317 ret |= of_property_read_u32(info_np, "ac-bias-intrpt", &info->ac_bias_intrpt); 318 ret |= of_property_read_u32(info_np, "dma-burst-sz", &info->dma_burst_sz); 319 ret |= of_property_read_u32(info_np, "bpp", &info->bpp); 320 ret |= of_property_read_u32(info_np, "fdd", &info->fdd); 321 ret |= of_property_read_u32(info_np, "sync-edge", &info->sync_edge); 322 ret |= of_property_read_u32(info_np, "sync-ctrl", &info->sync_ctrl); 323 ret |= of_property_read_u32(info_np, "raster-order", &info->raster_order); 324 ret |= of_property_read_u32(info_np, "fifo-th", &info->fifo_th); 325 326 /* optional: */ /* 這是可選選項，下面第二個則是時鐘反轉的選項。在設備中添加一個選項即可。 */ 327 info->tft_alt_mode = of_property_read_bool(info_np, "tft-alt-mode"); 328 info->invert_pxl_clk = of_property_read_bool(info_np, "invert-pxl-clk"); 329 330 if (ret) { 331 pr_err("%s: error reading panel-info properties\n", __func__); 332 kfree(info); 333 of_node_put(info_np); 334 return NULL; 335 } 336 of_node_put(info_np); 337 338 return info; 339 } /* 設備樹修改 */47 panel { 48 compatible = "ti,tilcdc,panel"; 49 status = "okay"; 50 pinctrl-names = "default"; 51 pinctrl-0 = <&lcd_pins_s0>; 52 panel-info { 53 ac-bias = <255>; 54 ac-bias-intrpt = <0>; 55 dma-burst-sz = <16>; 56 bpp = <16>; 57 fdd = <0x80>; 58 sync-edge = <0>; 59 sync-ctrl = <1>; 60 raster-order = <0>; 61 fifo-th = <0>; 62 invert-pxl-clk = <1>; /* 添加這個選項設置為1 */ 63 };重新編譯設備樹，重新啟動，看效果。

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