On 07/18/2012 03:31 PM, Manjunathappa, Prakash wrote: > Flicker/tearing effect is observed with current FB driver. > Issue is because of 2 active DMA channels ping ponging among them > along with usage of 2 DDR ping pong buffers in driver. Application > unaware of active DMA channel keeps updating frame being displayed, > this leads to tearing effect. > Below steps describes the issue: > 1)Initially assume both buffers FB0 and FB1 are programmed for buffer-0. > 2)On EOF0: Program FB0 for buffer-1, indicate(wake up) application > to fill up buffer-0. As FB1 is active and continues to DMA buffer-0 > (which is being filled), leading to tearing/flickering issue. > 3)On EOF1: Program FB1 for buffer-0, indicate(wake up) application to > fill up buffer-1. As FB0 is active and continues to DMA buffer-1(which > is being filled), leading to tearing/flickering issue. > 4)On EOF0: Program FB0 for buffer-1, indicate(wake up) application to > fill up buffer-0. As FB1 is active and continues to DMA buffer-0(which is > being filled), leading to tearing/flickering issue. > ... > Above steps depict that issue is because of 1 frame delay in frame > panned by application. > > Patch fixes the issue by keeping track free DMA channel and configures > it in drivers PAN callback so that panned frame from application gets > displayed in next frame period. > > Wiki below describes the issue in detail and it also has link to > application with which issue can be reproduced. > http://processors.wiki.ti.com/index.php/DA8xx_LCDC_Linux_FB_FAQs > > Signed-off-by: Nellutla, Aditya <aditya.n@xxxxxx> > Signed-off-by: Manjunathappa, Prakash <prakash.pm@xxxxxx> Applied. Thanks, Florian Tobias Schandinat > --- > Resending as my earlier patch seems like not reached fbdev mailing list. > > drivers/video/da8xx-fb.c | 30 ++++++++++++++++++++++++++++++ > 1 files changed, 30 insertions(+), 0 deletions(-) > > diff --git a/drivers/video/da8xx-fb.c b/drivers/video/da8xx-fb.c > index e9d2f6e..183366d 100644 > --- a/drivers/video/da8xx-fb.c > +++ b/drivers/video/da8xx-fb.c > @@ -30,6 +30,7 @@ > #include <linux/clk.h> > #include <linux/cpufreq.h> > #include <linux/console.h> > +#include <linux/spinlock.h> > #include <linux/slab.h> > #include <video/da8xx-fb.h> > #include <asm/div64.h> > @@ -161,6 +162,13 @@ struct da8xx_fb_par { > wait_queue_head_t vsync_wait; > int vsync_flag; > int vsync_timeout; > + spinlock_t lock_for_chan_update; > + > + /* > + * LCDC has 2 ping pong DMA channels, channel 0 > + * and channel 1. > + */ > + unsigned int which_dma_channel_done; > #ifdef CONFIG_CPU_FREQ > struct notifier_block freq_transition; > unsigned int lcd_fck_rate; > @@ -741,6 +749,7 @@ static irqreturn_t lcdc_irq_handler_rev02(int irq, void *arg) > lcdc_write(stat, LCD_MASKED_STAT_REG); > > if (stat & LCD_END_OF_FRAME0) { > + par->which_dma_channel_done = 0; > lcdc_write(par->dma_start, > LCD_DMA_FRM_BUF_BASE_ADDR_0_REG); > lcdc_write(par->dma_end, > @@ -750,6 +759,7 @@ static irqreturn_t lcdc_irq_handler_rev02(int irq, void *arg) > } > > if (stat & LCD_END_OF_FRAME1) { > + par->which_dma_channel_done = 1; > lcdc_write(par->dma_start, > LCD_DMA_FRM_BUF_BASE_ADDR_1_REG); > lcdc_write(par->dma_end, > @@ -796,6 +806,7 @@ static irqreturn_t lcdc_irq_handler_rev01(int irq, void *arg) > lcdc_write(stat, LCD_STAT_REG); > > if (stat & LCD_END_OF_FRAME0) { > + par->which_dma_channel_done = 0; > lcdc_write(par->dma_start, > LCD_DMA_FRM_BUF_BASE_ADDR_0_REG); > lcdc_write(par->dma_end, > @@ -805,6 +816,7 @@ static irqreturn_t lcdc_irq_handler_rev01(int irq, void *arg) > } > > if (stat & LCD_END_OF_FRAME1) { > + par->which_dma_channel_done = 1; > lcdc_write(par->dma_start, > LCD_DMA_FRM_BUF_BASE_ADDR_1_REG); > lcdc_write(par->dma_end, > @@ -1050,6 +1062,7 @@ static int da8xx_pan_display(struct fb_var_screeninfo *var, > struct fb_fix_screeninfo *fix = &fbi->fix; > unsigned int end; > unsigned int start; > + unsigned long irq_flags; > > if (var->xoffset != fbi->var.xoffset || > var->yoffset != fbi->var.yoffset) { > @@ -1067,6 +1080,21 @@ static int da8xx_pan_display(struct fb_var_screeninfo *var, > end = start + fbi->var.yres * fix->line_length - 1; > par->dma_start = start; > par->dma_end = end; > + spin_lock_irqsave(&par->lock_for_chan_update, > + irq_flags); > + if (par->which_dma_channel_done == 0) { > + lcdc_write(par->dma_start, > + LCD_DMA_FRM_BUF_BASE_ADDR_0_REG); > + lcdc_write(par->dma_end, > + LCD_DMA_FRM_BUF_CEILING_ADDR_0_REG); > + } else if (par->which_dma_channel_done == 1) { > + lcdc_write(par->dma_start, > + LCD_DMA_FRM_BUF_BASE_ADDR_1_REG); > + lcdc_write(par->dma_end, > + LCD_DMA_FRM_BUF_CEILING_ADDR_1_REG); > + } > + spin_unlock_irqrestore(&par->lock_for_chan_update, > + irq_flags); > } > } > > @@ -1294,6 +1322,8 @@ static int __devinit fb_probe(struct platform_device *device) > /* initialize the vsync wait queue */ > init_waitqueue_head(&par->vsync_wait); > par->vsync_timeout = HZ / 5; > + par->which_dma_channel_done = -1; > + spin_lock_init(&par->lock_for_chan_update); > > /* Register the Frame Buffer */ > if (register_framebuffer(da8xx_fb_info) < 0) { -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
