linux-kernel - [PATCH] axis-fifo: Remove hardware resets for user errors

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Message-ID: <20250419004306.669605-1-gshahrouzi@gmail.com>
Date: Fri, 18 Apr 2025 20:43:06 -0400
From: Gabriel Shahrouzi <gshahrouzi@...il.com>
To: gregkh@...uxfoundation.org,
	gshahrouzi@...il.com,
	jacobsfeder@...il.com,
	linux-kernel@...r.kernel.org,
	linux-staging@...ts.linux.dev,
	sergio.paracuellos@...il.com
Cc: skhan@...uxfoundation.org,
	linux-kernel-mentees@...ts.linux.dev,
	stable@...r.kernel.org
Subject: [PATCH] axis-fifo:  Remove hardware resets for user errors

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.

Fixes: 4a965c5f89de ("staging: add driver for Xilinx AXI-Stream FIFO v4.1 IP core")
Cc: stable@...r.kernel.org
Signed-off-by: Gabriel Shahrouzi <gshahrouzi@...il.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");
 		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);
 			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);
 			ret = -EFAULT;
 			goto end_unlock;
 		}
-- 
2.43.0