On Fri, Apr 18, 2025 at 08:43:06PM -0400, Gabriel Shahrouzi wrote:

The axis-fifo driver performs a full hardware reset (via reset_ip_core()) in several error paths within the read and write functions. This reset flushes both TX and RX FIFOs and resets the AXI-Stream links.

Allow the user to handle the error without causing hardware disruption or data loss in other FIFO paths.

I agree with the sentiment behind these changes, but they are basically impossible to review. The reset_ip_core() does some magic stuff in the firmware and I don't have access to that. How are you testing these changes?

Fixes: 4a965c5f89de ("staging: add driver for Xilinx AXI-Stream FIFO v4.1 IP core") Cc: stable@vger.kernel.org Signed-off-by: Gabriel Shahrouzi gshahrouzi@gmail.com

---

drivers/staging/axis-fifo/axis-fifo.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/staging/axis-fifo/axis-fifo.c b/drivers/staging/axis-fifo/axis-fifo.c index 7540c20090c78..76db29e4d2828 100644 --- a/drivers/staging/axis-fifo/axis-fifo.c +++ b/drivers/staging/axis-fifo/axis-fifo.c @@ -393,16 +393,14 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf, bytes_available = ioread32(fifo->base_addr + XLLF_RLR_OFFSET); if (!bytes_available) {

• dev_err(fifo->dt_device, "received a packet of length 0 - fifo core will be reset\n");
  

• reset_ip_core(fifo);
  

• dev_err(fifo->dt_device, "received a packet of length 0\n");
  

  ret = -EIO; goto end_unlock; }

if (bytes_available > len) {

• dev_err(fifo->dt_device, "user read buffer too small (available bytes=%zu user buffer bytes=%zu) - fifo core will be reset\n",
  

• dev_err(fifo->dt_device, "user read buffer too small (available bytes=%zu user buffer bytes=%zu)\n",
  bytes_available, len);
  

• reset_ip_core(fifo);
  

  ret = -EINVAL; goto end_unlock; }

@@ -411,8 +409,7 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf, /* this probably can't happen unless IP * registers were previously mishandled */

• dev_err(fifo->dt_device, "received a packet that isn't word-aligned - fifo core will be reset\n");
  

• reset_ip_core(fifo);
  

• dev_err(fifo->dt_device, "received a packet that isn't word-aligned\n");
  

The commit message talks about "user errors" but these aren't user errors so far as I can see.

ret = -EIO;
goto end_unlock;

} @@ -433,7 +430,6 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf, if (copy_to_user(buf + copied * sizeof(u32), tmp_buf, copy * sizeof(u32))) {

• 	reset_ip_core(fifo);
  

Yes. Absolutely. Delete this.

	ret = -EFAULT;
	goto end_unlock;
}

@@ -542,7 +538,6 @@ static ssize_t axis_fifo_write(struct file *f, const char __user *buf, if (copy_from_user(tmp_buf, buf + copied * sizeof(u32), copy * sizeof(u32))) {

• 	reset_ip_core(fifo);
  

Same. Delete.

This type of code is often written for a reason. Potentially as a hack to paper over a real bug. And then people get carried away adding resets all over the place. It's fine to delete the last two calls but I would be very careful to delete the others. Even though the patch might be correct it needs to be tested very carefully.

regards, dan carpenter

	ret = -EFAULT;
	goto end_unlock;
}

-- 2.43.0