Re: [PATCH 2/3] net: emaclite: fix xemaclite_alignedread/write functions

[Michal Simek]

On 8/6/22 19:33, Ramon Fried wrote:
On Wed, Jul 13, 2022 at 5:02 PM Samuel Obuch <samuel.ob...@codasip.com> wrote:

Use __raw_read* and __raw_write* functions to ensure read/write
is passed to the memory-mapped regions, as non-volatile accesses
may get optimised out.

Signed-off-by: Samuel Obuch <samuel.ob...@codasip.com>
---
  drivers/net/xilinx_emaclite.c | 9 ++++-----
  1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/net/xilinx_emaclite.c b/drivers/net/xilinx_emaclite.c
index 5cd88e04fe..de7a2dee0b 100644
--- a/drivers/net/xilinx_emaclite.c
+++ b/drivers/net/xilinx_emaclite.c
@@ -113,12 +113,12 @@ static void xemaclite_alignedread(u32 *srcptr, void 
*destptr, u32 bytecount)
         /* Word aligned buffer, no correction needed. */
         to32ptr = (u32 *) destptr;
         while (bytecount > 3) {
-               *to32ptr++ = *from32ptr++;
+               *to32ptr++ = __raw_readl(from32ptr++);
                 bytecount -= 4;
         }
         to8ptr = (u8 *) to32ptr;

-       alignbuffer = *from32ptr++;
+       alignbuffer = __raw_readl(from32ptr++);
         from8ptr = (u8 *) &alignbuffer;

         for (i = 0; i < bytecount; i++)
@@ -136,8 +136,7 @@ static void xemaclite_alignedwrite(void *srcptr, u32 
*destptr, u32 bytecount)

         from32ptr = (u32 *) srcptr;
         while (bytecount > 3) {
-
-               *to32ptr++ = *from32ptr++;
+               __raw_writel(*from32ptr++, to32ptr++);
                 bytecount -= 4;
         }

@@ -148,7 +147,7 @@ static void xemaclite_alignedwrite(void *srcptr, u32 
*destptr, u32 bytecount)
         for (i = 0; i < bytecount; i++)
                 *to8ptr++ = *from8ptr++;

-       *to32ptr++ = alignbuffer;
+       __raw_writel(alignbuffer, to32ptr++);
  }

  static int wait_for_bit(const char *func, u32 *reg, const u32 mask,
--
2.31.1

I think that using readl/writel is fine, no need for raw_...

For microblaze that should be fine but let me ask my team to rest it on ARM.
I think that __raw version are safer because this IP can also run on big endian 
systems and I think that was the reason why readl/writel wasn't used in past.

Thanks,
Michal