[alsa-devel] [PATCH] ASoC: SOF: imx8: Fix dsp_box offset

[Pierre-Louis Bossart]

From: Daniel Baluta <daniel.baluta at nxp.com>

dsp_box is used to keep DSP initiated messages. The value of dsp_offset
is set by the DSP with the first message, so we need a way to bootstrap
it in order to get the first message.

We do this by setting the correct default dsp_box offset which on i.MX8
is not zero.

Very interesting is why it has worked until now.

On i.MX8, DSP communicates with ARM core using a shared SDRAM memory
area. Actually, there are two shared areas:
	* SDRAM0 - starting at 0x92400000, size 0x800000
	* SDRAM1 - starting at 0x92C00000, size 0x800000

SDRAM0 keeps the data sections, starting with .rodata. By chance
fw_ready structure was placed at the beginning of .rodata.

dsp_box_base is defined as SDRAM0 + dsp_box_offset and it is placed
at the beginning of SDRAM1 (dsp_box_offset should be 0x800000). But
because it is zero initialized by default it points to SDRAM0 where
by chance the fw_ready was placed in the SOF firmware.

Anyhow, SOF commit 7466bee378dd811b ("clk: make freq arrays constant")
fw_ready is no longer at the beginning of SDRAM0 and everything shows
how lucky we were until now.

Fix this by properly setting the default dsp_box offset.

Fixes: 202acc565a1f050 ("ASoC: SOF: imx: Add i.MX8 HW support")
Signed-off-by: Daniel Baluta <daniel.baluta at nxp.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 sound/soc/sof/imx/imx8.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/soc/sof/imx/imx8.c b/sound/soc/sof/imx/imx8.c
index cfefcfd92798..dca85cf07ffa 100644
--- a/sound/soc/sof/imx/imx8.c
+++ b/sound/soc/sof/imx/imx8.c
@@ -304,6 +304,9 @@ static int imx8_probe(struct snd_sof_dev *sdev)
 	}
 	sdev->mailbox_bar = SOF_FW_BLK_TYPE_SRAM;
 
+	/* set default mailbox offset for FW ready message */
+	sdev->dsp_box.offset = MBOX_OFFSET;
+
 	return 0;
 
 exit_pdev_unregister:
-- 
2.20.1