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>
diff --git a/drivers/video/atmel_lcdfb.c b/drivers/video/atmel_lcdfb.c
index b004036..d335bb9 100644
--- a/drivers/video/atmel_lcdfb.c
+++ b/drivers/video/atmel_lcdfb.c
@@ -379,6 +379,35 @@
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 @@
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 @@
/* 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 @@
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 @@
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 @@
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 @@
if (!sinfo)
return 0;
+ cancel_work_sync(&sinfo->task);
exit_backlight(sinfo);
if (sinfo->atmel_lcdfb_power_control)
sinfo->atmel_lcdfb_power_control(0);