EDMA[Known Issue]: (aws#317)

1. Update the release notes with the known issue. 2. Update the tests according to the above issue.
wjblanke · Apr 21, 2017 · 324e9aa · 324e9aa
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diff --git a/sdk/linux_kernel_drivers/edma/RELEASE_NOTES.md b/sdk/linux_kernel_drivers/edma/RELEASE_NOTES.md
@@ -1,14 +1,19 @@
-# EDMA Driver Release notes 
+# EDMA Driver Release Notes 
 
-This is first release of the EDMA driver. This driver is still under development and performance may not be achieving maximal potential.
+This is the first release of the EDMA driver. This driver is still under development and performance may not be achieving maximal potential.
 
 This is a Linux kernel driver only
 
 ## Supported Distributions
 - Amazon Linux
 - Centos 7.x
-- More ditributions will be tested later.
+- More distributions will be tested later.
+
+## Known Issues
+- Reads, in rare cases, might lead to a software hang. To avoid the hang, please do one of the following:
+ - The address being read is 4K aligned. i.e. bits 0:11 are 0. Any read size is supported.
+ - Reading from an address that is not 4K aligned should not cross to the next 4K page.
 
 ## Expected performance
 - For smaller block size write performance is around 10MByte/s, read performance is around 150MByte/s
-- For a block size of 64KByte the expected performance is around 80MByte/s for write and 1GByte/s for read.
+- For a block size of 64KByte, the expected performance is around 80MByte/s for write and 1GByte/s for read.
diff --git a/sdk/linux_kernel_drivers/edma/unit-test/mt_read_write.c b/sdk/linux_kernel_drivers/edma/unit-test/mt_read_write.c
@@ -132,6 +132,10 @@ void* doRead(void *arg)
 
 		read_size = can_read == 1 ? 1: rand() % can_read;
 
+		//check if we cross a 4k page
+		if((offset % PAGE_SIZE + read_size) > PAGE_SIZE)
+			read_size = PAGE_SIZE - offset % PAGE_SIZE;
+
 		ret = lseek(fd, offset, SEEK_SET);
 		if(ret < 0)
 			exit(3);