imx233: workaround hardware dma bug

This bug mostly affects the ZEN and ZEN X-Fi and hangs the lcdif dma randomly
on boot.

Change-Id: I4255db90d87737b7a70d1d53e3ef84e4e14c8c13

1 files changed, 34 insertions, 0 deletions

diff --git a/firmware/target/arm/imx233/dma-imx233.c b/firmware/target/arm/imx233/dma-imx233.c
index 390add481b..fa8ee074bb 100644
--- a/firmware/target/arm/imx233/dma-imx233.c
+++ b/firmware/target/arm/imx233/dma-imx233.c
@@ -32,8 +32,42 @@
 // statistics about unaligned transfers
 static int apb_nr_unaligned[32];
 
+static void safe_reset_channel(int chan)
+{
+    bool apbx_running = !BF_RD(APBX_CTRL0, SFTRST) && !BF_RD(APBX_CTRL0, CLKGATE);
+    bool apbh_running = !BF_RD(APBH_CTRL0, SFTRST) && !BF_RD(APBH_CTRL0, CLKGATE);
+    if(APB_IS_APBX_CHANNEL(chan))
+    {
+        if(!apbx_running)
+            return; /* don't reset if block is not running */
+    }
+    else
+    {
+        if(!apbh_running)
+            return; /* don't reset if block is not running */
+        if(BF_RD(APBH_CTRL0, CLKGATE_CHANNEL) & (1 << chan))
+            return; /* don't reset a gated channel */
+    }
+    imx233_dma_reset_channel(chan);
+}
+
 void imx233_dma_init(void)
 {
+    /* BUG The stmp3700 (and probably stmp3780) have a hardware bug related to
+     * resetting the block when channel is running. It appears that at least
+     * for the LCDIF channel, resetting the block while the channel is running
+     * will make the channel hang. Once the channel hang, it cannot be recovered
+     * except by a chip reset. On most devices this situation will never arise
+     * but on the Creative ZEN (X-Fi), the OF bootloader leaves the channel
+     * running (to display the logo) when booting. It is unclear if this bug only
+     * affects the APBH or also the APBX. I believe it is related to the errata about
+     * channels not clearing the fifo on abrupt termination which affects both
+     * dma engines. Also note that we can't safely reset 'all' the channels by
+     * setting the reset mask to 0xffff since non-implemented channels don't clear
+     * their reset bit... Also reset won't work on gated channels and won't work if
+     * block is in reset or gated, in which case this situation is assumed not
+     * to exists */
+    safe_reset_channel(APB_LCDIF);
     /* Enable APHB and APBX */
     imx233_reset_block(&HW_APBH_CTRL0);
     imx233_reset_block(&HW_APBX_CTRL0);