From 20a1ea2222e7cbf96e9bf8579362e971491e6aea Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Wed, 3 Jan 2018 16:38:46 +0100
Subject: [PATCH] ASoC: skl: Fix kernel warning due to zero NHTL entry
Git-commit: 20a1ea2222e7cbf96e9bf8579362e971491e6aea
Patch-mainline: v4.16-rc1
References: bsc#1051510

I got the following kernel warning when loading snd-soc-skl module on
Dell Latitude 7270 laptop:
 memremap attempted on mixed range 0x0000000000000000 size: 0x0
 WARNING: CPU: 0 PID: 484 at kernel/memremap.c:98 memremap+0x8a/0x180
 Call Trace:
  skl_nhlt_init+0x82/0xf0 [snd_soc_skl]
  skl_probe+0x2ee/0x7c0 [snd_soc_skl]
  ....

It seems that the machine doesn't support the SKL DSP gives the empty
NHLT entry, and it triggers the warning.  For avoiding it, let do the
zero check before calling memremap().

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

---
 sound/soc/intel/skylake/skl-nhlt.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/sound/soc/intel/skylake/skl-nhlt.c
+++ b/sound/soc/intel/skylake/skl-nhlt.c
@@ -41,7 +41,8 @@ struct nhlt_acpi_table *skl_nhlt_init(st
 	obj = acpi_evaluate_dsm(handle, &osc_guid, 1, 1, NULL);
 	if (obj && obj->type == ACPI_TYPE_BUFFER) {
 		nhlt_ptr = (struct nhlt_resource_desc  *)obj->buffer.pointer;
-		nhlt_table = (struct nhlt_acpi_table *)
+		if (nhlt_ptr->length)
+			nhlt_table = (struct nhlt_acpi_table *)
 				memremap(nhlt_ptr->min_addr, nhlt_ptr->length,
 				MEMREMAP_WB);
 		ACPI_FREE(obj);