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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: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nicolas Ferre 2008-07-23 21:31:20 -07:00 committed by Linus Torvalds
parent 77a6e7abb0
commit d22579b837
2 changed files with 57 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
drivers/video/atmel_lcdfb.c
View File

@ -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);

1
include/video/atmel_lcdc.h
View File

@ -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;