Hi,
Finally I could able to find the root-cause, actually some of the previous
observations miss-led me to dig into power management, suspend/resume path and
clock structure. But after bit debugging and with the help of Sanjeev, we got
the rid of it.
The issue is with DSS2 library, inside function "dpi_display_suspend". It calls
dispc_enable_lcd_out(0), but doesn't wait till the frame-done interrupt. And
due to this I was getting some abrupt behavior in suspend/resume path.
Actually in the beginning I overlooked legacy frame-buffer driver, which
handles this scenario perfectly.
For Display sub-system we have 2 interface clocks coming, L3_ICLK and L4_ICLK.
Out of these, L4_ICLK goes to Display register access and L3_ICLK goes to DMA
register. In our suspend call we are disabling clocks for L3_ICLK (we don't
control L4_ICLK), and due to this L4_ICLK stays attached with GFX. You will
only be able to find out this by looking to CM_CLKSTST_DSS.CLKACTIVITY_DSS,
which is set 1 and indicates some interface clock is still active in DSS domain.
Below is the patch which will explain the change
+#include <linux/completion.h>
+#include <linux/jiffies.h>
+static void dpi_display_isr(void *arg, unsigned int irqstatus)
+{
+ struct omap_display *display = (struct omap_display *)arg;
+
+ complete(&display->frame_done);
+}
static int dpi_display_suspend(struct omap_display *display)
{
+ void *handle = NULL;
+
if (display->state != OMAP_DSS_DISPLAY_ACTIVE)
return -EINVAL;
if (display->panel->suspend)
display->panel->suspend(display);
+ /*
+ * Wait for frame done interrupt
+ */
+ handle = omap_dispc_register_isr(dpi_display_isr, display,
+ DISPC_IRQ_FRAMEDONE);
+ if (!handle)
+ return -EINVAL;
+
+ init_completion(&display->frame_done);
+
dispc_enable_lcd_out(0);
+ if (!wait_for_completion_timeout(&display->frame_done,
+ msecs_to_jiffies(500))) {
+ printk("timeout waiting for FRAME DONE\n");
+ }
Still I need to test this thoroughly, I may hit some another issue (Already I
am seeing some crashes also when off state is enabled). I will create
consolidated patch for this and will submit to list.
Thanks,
Vaibhav Hiremath
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