imx233: make sure dma descriptors are cache friendly

Because DMA descriptors needs to be committed and discarded from
the cache, if they are not cache aligned and/or if their size
is not a multiple of cache ligne, nasty side effects could occur
with adjacents data. The same applies to DMA buffers which are
still potentially broken. Add a macro to ensure that these
constraints will not break by error in the future.

Change-Id: I1dd69a5a9c29796c156d953eaa57c0d281e79846

firmware/export/imx233.h

@@ -86,6 +86,12 @@
 /* 32 bytes per cache line */
 #define CACHEALIGN_BITS     5
 
+#define ___ENSURE_ZERO(line, x) static uint8_t __ensure_zero_##line[-(x)] __attribute__((unused));
+#define __ENSURE_ZERO(x) ___ENSURE_ZERO(__LINE__, x)
+#define __ENSURE_MULTIPLE(x, y) __ENSURE_ZERO((x) % (y))
+#define __ENSURE_CACHELINE_MULTIPLE(x) __ENSURE_MULTIPLE(x, 1 << CACHEALIGN_BITS)
+#define __ENSURE_STRUCT_CACHE_FRIENDLY(name) __ENSURE_CACHELINE_MULTIPLE(sizeof(name))
+
 #define __XTRACT(reg, field)    ((reg & reg##__##field##_BM) >> reg##__##field##_BP)
 #define __XTRACT_EX(val, field)    (((val) & field##_BM) >> field##_BP)
 #define __FIELD_SET(reg, field, val) reg = (reg & ~reg##__##field##_BM) | (val << reg##__##field##_BP)

firmware/target/arm/imx233/dma-imx233.h

@@ -118,6 +118,10 @@
  * COMMON *
  **********/
 
+/* DMA structures should be cache aligned and be padded so that their size
+ * is a multiple of a cache line size. Otherwise some nasty side effects
+ * could occur with adjacents data fields.
+ * The same apply to DMA buffers for the same reasons */
 struct apb_dma_command_t
 {
     struct apb_dma_command_t *next;

firmware/target/arm/imx233/i2c-imx233.c

@@ -34,7 +34,11 @@ struct i2c_dma_command_t
     struct apb_dma_command_t dma;
     /* PIO words */
     uint32_t ctrl0;
-};
+    /* padded to next multiple of cache line size (32 bytes) */
+    uint32_t pad[4];
+} __attribute__((packed)) CACHEALIGN_ATTR;
+
+__ENSURE_STRUCT_CACHE_FRIENDLY(struct i2c_dma_command_t)
 
 #define I2C_NR_STAGES   4
 /* Current transfer */

firmware/target/arm/imx233/pcm-imx233.c

@@ -26,8 +26,17 @@
 #include "pcm-internal.h"
 #include "audioout-imx233.h"
 
+struct pcm_dma_command_t
+{
+    struct apb_dma_command_t dma;
+    /* padded to next multiple of cache line size (32 bytes) */
+    uint32_t pad[5];
+} __attribute__((packed)) CACHEALIGN_ATTR;
+
+__ENSURE_STRUCT_CACHE_FRIENDLY(struct pcm_dma_command_t)
+
 static int locked = 0;
-static struct apb_dma_command_t dac_dma;
+static struct pcm_dma_command_t dac_dma;
 static bool pcm_freezed = false;
 
 /**
@@ -37,14 +46,14 @@ static bool pcm_freezed = false;
 
 static void play(const void *addr, size_t size)
 {
-    dac_dma.next = NULL;
+    dac_dma.dma.next = NULL;
-    dac_dma.buffer = (void *)addr;
+    dac_dma.dma.buffer = (void *)addr;
-    dac_dma.cmd = HW_APB_CHx_CMD__COMMAND__READ |
+    dac_dma.dma.cmd = HW_APB_CHx_CMD__COMMAND__READ |
         HW_APB_CHx_CMD__IRQONCMPLT |
         HW_APB_CHx_CMD__SEMAPHORE |
         size << HW_APB_CHx_CMD__XFER_COUNT_BP;
     /* dma subsystem will make sure cached stuff is written to memory */
-    imx233_dma_start_command(APB_AUDIO_DAC, &dac_dma);
+    imx233_dma_start_command(APB_AUDIO_DAC, &dac_dma.dma);
 }
 
 void INT_DAC_DMA(void)

firmware/target/arm/imx233/ssp-imx233.c

@@ -43,7 +43,11 @@ struct ssp_dma_command_t
     uint32_t ctrl0;
     uint32_t cmd0;
     uint32_t cmd1;
-};
+    /* padded to next multiple of cache line size (32 bytes) */
+    uint32_t pad[2];
+} __attribute__((packed)) CACHEALIGN_ATTR;
+
+__ENSURE_STRUCT_CACHE_FRIENDLY(struct ssp_dma_command_t)
 
 static bool ssp_in_use[2];
 static int ssp_nr_in_use = 0;