bug fixes and updates to common/driver

[ruck314]

Description

• use readl() and writel() instead of ioread32() and iowrite32()
  • These changes replace the direct I/O access functions with the recommended memory-mapped I/O functions, improving portability and security within the kernel module.
• Switching to kzalloc to automatically zero out the allocated memory can be beneficial for several reasons:
  • Security: Automatically zeroing memory can help prevent the unintentional leak of sensitive information from previously used memory blocks.
  • Stability: Initializing memory to zero can prevent bugs related to uninitialized memory usage.
  • Simplicity: Using kzalloc simplifies the code by combining allocation and initialization into a single operation, reducing the risk of forgetting to explicitly zero the memory.
• changing GFP_DMA32 to GFP_DMA
  • Using GFP_DMA for DMA allocations in a kernel code that runs on a 32-bit system should not inherently cause an error just because of the flag's usage. The GFP_DMA flag is used to indicate that the allocated memory is DMA-able, and it's generally used for devices that require direct access to physical memory without going through the CPU's caching mechanisms. This flag is not specifically tied to 32-bit or 64-bit addressing; it's more about the requirements of the device and the DMA (Direct Memory Access) system.
• remap_pfn_range() is deprecated in favor of functions like ioremap_pfn_range()
• dma_map_single() being depreciated in future and switching to dma_alloc_coherent()
  • offers simplified management, potentially better performance, reduced fragmentation, and safer memory access for your DMA operations
• replacing IOREMAP_NO_CACHE with ioremap_wc
  • This change adapts the code to be compliant with the new kernel requirements by using ioremap_wc for write-combining mappings, which is recommended for device memory mappings that do not require caching. This adjustment ensures that the driver remains functional and efficient under the updated kernel API.
  • The ioremap_wc() function was first introduced in the Linux kernel version 2.6.15, released on January 21, 2006.

[ruck314]

Confirmed this worked using DMA loopback firmware on the following Linux kernels:

• 5.15.0-94-generic
• 6.5.0-18-generic
• 6.1.30-xilinx-v2023.2