atmel_lcdfb: Disable LCD and DMA engines when suspending

When suspending the system with atmel_lcdfb enabled, I sometimes see
this:

[17179610.896000] atmel_lcdfb atmel_lcdfb.0: FIFO underflow 0x10

After this happens, the serial console is unresponsive for a long time,
but eventually recovers (after a minute or so).  SysRq-W shows that the
events thread is blocked trying to recover from the underflow:

SysRq : Show Blocked State
  task                PC stack   pid father
events/0      D 90169e50     0     5      2
Stack: (0x93833ebc to 0x93834000)
3ea0:                                                                93832008
3ec0: 90169fd8 90169fd8 93833f18 ffff11ce 93833ee8 00000000 901fb560 00000004
3ee0: 901c7788 00000000 902254f8 902254f8 ffff11ce 90023884 9381b900 90225460
3f00: 90169fd6 6576656e 74732f30 00000000 00000000 00000005 9016a012 93833f3c
3f20: 9388ca40 93821000 00000000 93832000 00000000 901c7788 00000000 90023d16
3f40: 93833f50 9388ca40 93821000 00000000 900c7ed2 93833f64 9388ca40 93821000
3f60: 00000000 90028156 93833f90 9388ca6c 93821000 00000000 90028110 900c7eb8
3f80: 904b7754 00000000 901c7788 00000000 900285a8 93833fc8 93832000 93832000
3fa0: 00000000 93821000 ffffe000 9002a7bc 93817eec 00000000 9381b900 9002aa14
3fc0: 93833fc0 93833fc0 9002a7e8 93833fec 93821000 900284f8 00000000 00000000
3fe0: 9001f718 9002a7bc 93817eec 9001f718 00000000 00000000 00000000 00000000
Call trace:
 [<90169fd8>] schedule_timeout+0x60/0x88
 [<9016a012>] schedule_timeout_uninterruptible+0x12/0x14
 [<90023d16>] msleep+0x12/0x1c
 [<900c7ed2>] atmel_lcdfb_task+0x1a/0x5c
 [<90028156>] run_workqueue+0xba/0x168
 [<900285a8>] worker_thread+0xb0/0xbc
 [<9002a7e8>] kthread+0x2c/0x44
 [<9001f718>] do_exit+0x0/0x508

Which is understandable since stopping the bus clock while the LCD
controller is doing a DMA transfer is a thoroughly nasty thing to do,
and the strange thing isn't that the controller gets confused, but that
it somehow actually manages to recover after a while.

Avoid this issue by shutting down the LCD controller before entering

19 more lines

diff --git a/drivers/video/atmel_lcdfb.c b/drivers/video/atmel_lcdfb.c
index 763f9ae..a42406a 100644
--- a/drivers/video/atmel_lcdfb.c
+++ b/drivers/video/atmel_lcdfb.c

@@ -206,6 +206,36 @@ static unsigned long compute_hozval(unsigned long xres, unsigned long lcdcon2)
 	return value;
 }
 
+static void atmel_lcdfb_stop_nowait(struct atmel_lcdfb_info *sinfo)
+{
+	/* Turn off the LCD controller and the DMA controller */
+	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);
+
+	lcdc_writel(sinfo, ATMEL_LCDC_DMACON, 0);
+}
+
+static void atmel_lcdfb_stop(struct atmel_lcdfb_info *sinfo)
+{
+	atmel_lcdfb_stop_nowait(sinfo);
+
+	/* Wait for DMA engine to become idle... */
+	while (lcdc_readl(sinfo, ATMEL_LCDC_DMACON) & ATMEL_LCDC_DMABUSY)
+		msleep(10);
+}
+
+static void atmel_lcdfb_start(struct atmel_lcdfb_info *sinfo)
+{
+	lcdc_writel(sinfo, ATMEL_LCDC_DMACON, sinfo->default_dmacon);
+	lcdc_writel(sinfo, ATMEL_LCDC_PWRCON,
+		(sinfo->guard_time << ATMEL_LCDC_GUARDT_OFFSET)
+		| ATMEL_LCDC_PWR);
+}
+
 static void atmel_lcdfb_update_dma(struct fb_info *info,
 			       struct fb_var_screeninfo *var)
 {

@@ -416,26 +446,8 @@ 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_stop(sinfo);
+	atmel_lcdfb_start(sinfo);
 }
 
 /**

@@ -467,14 +479,7 @@ static int atmel_lcdfb_set_par(struct fb_info *info)
 		 info->var.xres, info->var.yres,
 		 info->var.xres_virtual, info->var.yres_virtual);
 
-	/* Turn off the LCD controller and the DMA controller */
-	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);
-
-	lcdc_writel(sinfo, ATMEL_LCDC_DMACON, 0);
+	atmel_lcdfb_stop_nowait(sinfo);
 
 	if (info->var.bits_per_pixel == 1)
 		info->fix.visual = FB_VISUAL_MONO01;

@@ -579,13 +584,7 @@ static int atmel_lcdfb_set_par(struct fb_info *info)
 	while (lcdc_readl(sinfo, ATMEL_LCDC_DMACON) & ATMEL_LCDC_DMABUSY)
 		msleep(10);
 
-	dev_dbg(info->device, "  * re-enable DMA engine\n");
-	/* ...and enable it with updated configuration */
-	lcdc_writel(sinfo, ATMEL_LCDC_DMACON, sinfo->default_dmacon);
-
-	dev_dbg(info->device, "  * re-enable LCDC core\n");
-	lcdc_writel(sinfo, ATMEL_LCDC_PWRCON,
-		(sinfo->guard_time << ATMEL_LCDC_GUARDT_OFFSET) | ATMEL_LCDC_PWR);
+	atmel_lcdfb_start(sinfo);
 
 	dev_dbg(info->device, "  * DONE\n");
 

@@ -1026,11 +1025,20 @@ static int atmel_lcdfb_suspend(struct platform_device *pdev, pm_message_t mesg)
 	struct fb_info *info = platform_get_drvdata(pdev);
 	struct atmel_lcdfb_info *sinfo = info->par;
 
+	/*
+	 * We don't want to handle interrupts while the clock is
+	 * stopped. It may take forever.
+	 */
+	lcdc_writel(sinfo, ATMEL_LCDC_IDR, ~0UL);
+
 	sinfo->saved_lcdcon = lcdc_readl(sinfo, ATMEL_LCDC_CONTRAST_VAL);
 	lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR, 0);
 	if (sinfo->atmel_lcdfb_power_control)
 		sinfo->atmel_lcdfb_power_control(0);
+
+	atmel_lcdfb_stop(sinfo);
 	atmel_lcdfb_stop_clock(sinfo);
+
 	return 0;
 }
 

@@ -1040,9 +1048,15 @@ static int atmel_lcdfb_resume(struct platform_device *pdev)
 	struct atmel_lcdfb_info *sinfo = info->par;
 
 	atmel_lcdfb_start_clock(sinfo);
+	atmel_lcdfb_start(sinfo);
 	if (sinfo->atmel_lcdfb_power_control)
 		sinfo->atmel_lcdfb_power_control(1);
 	lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR, sinfo->saved_lcdcon);
+
+	/* Enable FIFO & DMA errors */
+	lcdc_writel(sinfo, ATMEL_LCDC_IER, ATMEL_LCDC_UFLWI
+			| ATMEL_LCDC_OWRI | ATMEL_LCDC_MERI);
+
 	return 0;
 }
 

-- 
1.5.6.3


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On Mon, 11 Aug 2008 14:34:28 +0200
Haavard Skinnemoen [off-list ref] wrote:

When suspending the system with atmel_lcdfb enabled, I sometimes see
this:

[17179610.896000] atmel_lcdfb atmel_lcdfb.0: FIFO underflow 0x10

After this happens, the serial console is unresponsive for a long time,
but eventually recovers (after a minute or so).  SysRq-W shows that the
events thread is blocked trying to recover from the underflow:

SysRq : Show Blocked State
  task                PC stack   pid father
events/0      D 90169e50     0     5      2
Stack: (0x93833ebc to 0x93834000)
3ea0:                                                                93832008
3ec0: 90169fd8 90169fd8 93833f18 ffff11ce 93833ee8 00000000 901fb560 00000004
3ee0: 901c7788 00000000 902254f8 902254f8 ffff11ce 90023884 9381b900 90225460
3f00: 90169fd6 6576656e 74732f30 00000000 00000000 00000005 9016a012 93833f3c
3f20: 9388ca40 93821000 00000000 93832000 00000000 901c7788 00000000 90023d16
3f40: 93833f50 9388ca40 93821000 00000000 900c7ed2 93833f64 9388ca40 93821000
3f60: 00000000 90028156 93833f90 9388ca6c 93821000 00000000 90028110 900c7eb8
3f80: 904b7754 00000000 901c7788 00000000 900285a8 93833fc8 93832000 93832000
3fa0: 00000000 93821000 ffffe000 9002a7bc 93817eec 00000000 9381b900 9002aa14
3fc0: 93833fc0 93833fc0 9002a7e8 93833fec 93821000 900284f8 00000000 00000000
3fe0: 9001f718 9002a7bc 93817eec 9001f718 00000000 00000000 00000000 00000000
Call trace:
 [<90169fd8>] schedule_timeout+0x60/0x88
 [<9016a012>] schedule_timeout_uninterruptible+0x12/0x14
 [<90023d16>] msleep+0x12/0x1c
 [<900c7ed2>] atmel_lcdfb_task+0x1a/0x5c
 [<90028156>] run_workqueue+0xba/0x168
 [<900285a8>] worker_thread+0xb0/0xbc
 [<9002a7e8>] kthread+0x2c/0x44
 [<9001f718>] do_exit+0x0/0x508

Which is understandable since stopping the bus clock while the LCD
controller is doing a DMA transfer is a thoroughly nasty thing to do,
and the strange thing isn't that the controller gets confused, but that
it somehow actually manages to recover after a while.

Avoid this issue by shutting down the LCD controller before entering

6 more quoted lines

Acked-by: Krzysztof Helt <redacted>

Please send it to akpm@linux-foundation.org if you do not intend
to merge it through atmel/arm tree.

Regards,
Krzysztof

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Sprawdz >> http://link.interia.pl/f1edc 
	


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Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/