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Date: Fri, 16 May 2008 14:34:12 +0200
From: Nicolas Ferre <nicolas.ferre@...el.com>
To: linux-fbdev-devel@...ts.sourceforge.net,
"Antonino A. Daplas" <adaplas@...il.com>
CC: Haavard Skinnemoen <hskinnemoen@...el.com>,
Andrew Victor <linux@...im.org.za>,
Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: [PATCH] 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@...el.com>
---
drivers/video/atmel_lcdfb.c | 50 +++++++++++++++++++++++++++++++++-
include/video/atmel_lcdc.h | 1
2 files changed, 50 insertions(+), 1 deletion(-)
Index: include/video/atmel_lcdc.h
===================================================================
--- a/include/video/atmel_lcdc.h
+++ b/include/video/atmel_lcdc.h
@@ -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;
Index: drivers/video/atmel_lcdfb.c
===================================================================
--- a/drivers/video/atmel_lcdfb.c
+++ b/drivers/video/atmel_lcdfb.c
@@ -356,6 +356,33 @@ static int atmel_lcdfb_check_var(struct
return 0;
}
+/*
+ * LCD reset sequence
+ */
+static void atmel_lcdfb_reset(struct atmel_lcdfb_info *sinfo)
+{
+ /* 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
@@ -486,6 +513,8 @@ static int atmel_lcdfb_set_par(struct fb
/* 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)
@@ -620,10 +649,26 @@ static irqreturn_t atmel_lcdfb_interrupt
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;
@@ -795,6 +840,9 @@ static int __init atmel_lcdfb_probe(stru
goto unmap_mmio;
}
+ /* Initialize bottom half workqueue */
+ 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);
--
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