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Commit d22579b8 authored by Nicolas Ferre's avatar Nicolas Ferre Committed by Linus Torvalds
Browse files

atmel_lcdfb: FIFO underflow management 



Manage atmel_lcdfb FIFO underflow

Resetting the LCD and DMA allows to fix screen shifting after a FIFO
underflow.  It follows reset sequence from errata "LCD Screen Shifting
After a Reset".

Signed-off-by: default avatarNicolas Ferre <nicolas.ferre@atmel.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Andrew Victor <linux@maxim.org.za>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 77a6e7ab

drivers/video/atmel_lcdfb.c

+56 −1
Original line number Diff line number Diff line
@@ -379,6 +379,35 @@ static int atmel_lcdfb_check_var(struct fb_var_screeninfo *var, 
	return 0;

}



/*

 * LCD reset sequence

 */

static void atmel_lcdfb_reset(struct atmel_lcdfb_info *sinfo)

{

	might_sleep();



	/* LCD power off */

	lcdc_writel(sinfo, ATMEL_LCDC_PWRCON, sinfo->guard_time << ATMEL_LCDC_GUARDT_OFFSET);



	/* wait for the LCDC core to become idle */

	while (lcdc_readl(sinfo, ATMEL_LCDC_PWRCON) & ATMEL_LCDC_BUSY)

		msleep(10);



	/* DMA disable */

	lcdc_writel(sinfo, ATMEL_LCDC_DMACON, 0);



	/* wait for DMA engine to become idle */

	while (lcdc_readl(sinfo, ATMEL_LCDC_DMACON) & ATMEL_LCDC_DMABUSY)

		msleep(10);



	/* LCD power on */

	lcdc_writel(sinfo, ATMEL_LCDC_PWRCON,

		(sinfo->guard_time << ATMEL_LCDC_GUARDT_OFFSET) | ATMEL_LCDC_PWR);



	/* DMA enable */

	lcdc_writel(sinfo, ATMEL_LCDC_DMACON, sinfo->default_dmacon);

}



/**

 *      atmel_lcdfb_set_par - Alters the hardware state.

 *      @info: frame buffer structure that represents a single frame buffer
@@ -401,6 +430,8 @@ static int atmel_lcdfb_set_par(struct fb_info *info) 
	unsigned long clk_value_khz;

	unsigned long bits_per_line;



	might_sleep();



	dev_dbg(info->device, "%s:\n", __func__);

	dev_dbg(info->device, "  * resolution: %ux%u (%ux%u virtual)\n",

		 info->var.xres, info->var.yres,
@@ -511,6 +542,8 @@ static int atmel_lcdfb_set_par(struct fb_info *info) 


	/* Disable all interrupts */

	lcdc_writel(sinfo, ATMEL_LCDC_IDR, ~0UL);

	/* Enable FIFO & DMA errors */

	lcdc_writel(sinfo, ATMEL_LCDC_IER, ATMEL_LCDC_UFLWI | ATMEL_LCDC_OWRI | ATMEL_LCDC_MERI);



	/* ...wait for DMA engine to become idle... */

	while (lcdc_readl(sinfo, ATMEL_LCDC_DMACON) & ATMEL_LCDC_DMABUSY)
@@ -645,10 +678,26 @@ static irqreturn_t atmel_lcdfb_interrupt(int irq, void *dev_id) 
	u32 status;



	status = lcdc_readl(sinfo, ATMEL_LCDC_ISR);

	lcdc_writel(sinfo, ATMEL_LCDC_IDR, status);

	if (status & ATMEL_LCDC_UFLWI) {

		dev_warn(info->device, "FIFO underflow %#x\n", status);

		/* reset DMA and FIFO to avoid screen shifting */

		schedule_work(&sinfo->task);

	}

	lcdc_writel(sinfo, ATMEL_LCDC_ICR, status);

	return IRQ_HANDLED;

}



/*

 * LCD controller task (to reset the LCD)

 */

static void atmel_lcdfb_task(struct work_struct *work)

{

	struct atmel_lcdfb_info *sinfo =

		container_of(work, struct atmel_lcdfb_info, task);



	atmel_lcdfb_reset(sinfo);

}



static int __init atmel_lcdfb_init_fbinfo(struct atmel_lcdfb_info *sinfo)

{

	struct fb_info *info = sinfo->info;
@@ -824,6 +873,10 @@ static int __init atmel_lcdfb_probe(struct platform_device *pdev) 
		goto unmap_mmio;

	}



	/* Some operations on the LCDC might sleep and

	 * require a preemptible task context */

	INIT_WORK(&sinfo->task, atmel_lcdfb_task);



	ret = atmel_lcdfb_init_fbinfo(sinfo);

	if (ret < 0) {

		dev_err(dev, "init fbinfo failed: %d\n", ret);
@@ -866,6 +919,7 @@ static int __init atmel_lcdfb_probe(struct platform_device *pdev) 
free_cmap:

	fb_dealloc_cmap(&info->cmap);

unregister_irqs:

	cancel_work_sync(&sinfo->task);

	free_irq(sinfo->irq_base, info);

unmap_mmio:

	exit_backlight(sinfo);
@@ -903,6 +957,7 @@ static int __exit atmel_lcdfb_remove(struct platform_device *pdev) 
	if (!sinfo)

		return 0;



	cancel_work_sync(&sinfo->task);

	exit_backlight(sinfo);

	if (sinfo->atmel_lcdfb_power_control)

		sinfo->atmel_lcdfb_power_control(0);

include/video/atmel_lcdc.h

+1 −0
Original line number Diff line number Diff line
@@ -37,6 +37,7 @@ struct atmel_lcdfb_info { 
	struct fb_info		*info;

	void __iomem		*mmio;

	unsigned long		irq_base;

	struct work_struct	task;



	unsigned int		guard_time;

	struct platform_device	*pdev;