To generate the patch for the CWE-190 vulnerability, we need to follow the reasoning steps below:

### Step 1: Root Cause Analysis

- 1: Validate `ret`:
  - `ret` is declared as an `int`, which is a signed integer type.
  - The function `mxs_dcp_start_dma` is likely to return a status or error code, which is typically represented by an unsigned value.

- 2: Signed vs Unsigned:
  - Using a signed integer to store a value that is expected to be non-negative (like a status or error code) can lead to issues when the value exceeds the maximum limit of the signed integer type.
  - In this case, if the function returns a large value, it may be interpreted as a negative number due to integer overflow, leading to incorrect error handling.

- 3: Potential Vulnerability:
  - The vulnerability arises from the use of a signed integer to store a value that should be non-negative.
  - This can lead to incorrect error handling or unexpected behavior when the function returns a large value.

### Conclusion:
The vulnerable behavior in this code is due to the use of a signed integer to store a value that should be non-negative. This can lead to incorrect error handling or unexpected behavior when the function returns a large value.

### Step 2: Fixing Strategy

- A common fixing strategy for CWE-190 is to use an unsigned integer type to store values that are expected to be non-negative.
- In this case, changing the type of `ret` from `int` to `unsigned long` ensures that it can store large values without overflowing or being interpreted as negative.
- Therefore, the patch should be:
```
<     int ret;
---
>     unsigned long ret;
```
By making this change, we can prevent potential issues with integer overflow and ensure that the function returns accurate error codes.