FAILED: patch "[PATCH] igc: read before write to SRRCTL register" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 3ce29c17dc847bf4245e16aad78a7617afa96297
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023050757-reclusive-clinking-0d63@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

3ce29c17dc84 ("igc: read before write to SRRCTL register")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3ce29c17dc847bf4245e16aad78a7617afa96297 Mon Sep 17 00:00:00 2001
From: Song Yoong Siang <[email protected]>
Date: Tue, 2 May 2023 08:48:06 -0700
Subject: [PATCH] igc: read before write to SRRCTL register

igc_configure_rx_ring() function will be called as part of XDP program setup. If Rx hardware timestamp is enabled prio to XDP program setup, this timestamp enablement will be overwritten when buffer size is written into SRRCTL register.

Thus, this commit read the register value before write to SRRCTL register. This commit is tested by using xdp_hw_metadata bpf selftest tool. The tool enables Rx hardware timestamp and then attach XDP program to igc driver. It will display hardware timestamp of UDP packet with port number 9092. Below are detail of test steps and results.

Command on DUT:
sudo ./xdp_hw_metadata <interface name>

Command on Link Partner:
echo -n skb | nc -u -q1 <destination IPv4 addr> 9092

Result before this patch:
skb hwtstamp is not found!

Result after this patch:
found skb hwtstamp = 1677800973.642836757

Optionally, read PHC to confirm the values obtained are almost the same:
Command:
sudo ./testptp -d /dev/ptp0 -g
Result:
clock time: 1677800973.913598978 or Fri Mar 3 07:49:33 2023

index 7a992befca24..9f3827eda157 100644
@@ -87,8 +87,13 @@ union igc_adv_rx_desc {
 #define IGC_RXDCTL_SWFLUSH		0x04000000 /* Receive Software Flush */
 
 /* SRRCTL bit definitions */
-#define IGC_SRRCTL_BSIZEPKT_SHIFT		10 /* Shift _right_ */
-#define IGC_SRRCTL_BSIZEHDRSIZE_SHIFT		2  /* Shift _left_ */
-#define IGC_SRRCTL_DESCTYPE_ADV_ONEBUF	0x02000000
+#define IGC_SRRCTL_BSIZEPKT_MASK	GENMASK(6, 0)
+#define IGC_SRRCTL_BSIZEPKT(x)		FIELD_PREP(IGC_SRRCTL_BSIZEPKT_MASK, \
+					(x) / 1024) /* in 1 KB resolution */
+#define IGC_SRRCTL_BSIZEHDR_MASK	GENMASK(13, 8)
+#define IGC_SRRCTL_BSIZEHDR(x)		FIELD_PREP(IGC_SRRCTL_BSIZEHDR_MASK, \
+					(x) / 64) /* in 64 bytes resolution */
+#define IGC_SRRCTL_DESCTYPE_MASK	GENMASK(27, 25)
+#define IGC_SRRCTL_DESCTYPE_ADV_ONEBUF	FIELD_PREP(IGC_SRRCTL_DESCTYPE_MASK, 1)
 
 #endif /* _IGC_BASE_H */

index ba49728be919..1c4676882082 100644
@@ -640,8 +640,11 @@ static void igc_configure_rx_ring(struct igc_adapter *adapter,
 	else
 		buf_size = IGC_RXBUFFER_2048;
 
-	srrctl = IGC_RX_HDR_LEN << IGC_SRRCTL_BSIZEHDRSIZE_SHIFT;
-	srrctl |= buf_size >> IGC_SRRCTL_BSIZEPKT_SHIFT;
+	srrctl = rd32(IGC_SRRCTL(reg_idx));
+	srrctl &= ~(IGC_SRRCTL_BSIZEPKT_MASK | IGC_SRRCTL_BSIZEHDR_MASK |
+		    IGC_SRRCTL_DESCTYPE_MASK);
+	srrctl |= IGC_SRRCTL_BSIZEHDR(IGC_RX_HDR_LEN);
+	srrctl |= IGC_SRRCTL_BSIZEPKT(buf_size);
 	srrctl |= IGC_SRRCTL_DESCTYPE_ADV_ONEBUF;
 
 	wr32(IGC_SRRCTL(reg_idx), srrctl);