checkpatch: check for comment explaining rgmii(|-rxid|-txid) PHY modes

Historically, the RGMII PHY modes specified in Device Trees have been
used inconsistently, often referring to the usage of delays on the PHY
side rather than describing the board; many drivers still implement this
incorrectly.

Require a comment in Devices Trees using these modes (usually mentioning
that the delay is realized on the PCB), so we can avoid adding more
incorrect uses (or will at least notice which drivers still need to be
fixed).

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/bc112b8aa510cf9df9ab33178d122f234d0aebf7.1750756583.git.matthias.schiffer@ew.tq-group.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
index 76bd0dd..d5c47e5 100644 (file)
--- a/Documentation/dev-tools/checkpatch.rst
+++ b/Documentation/dev-tools/checkpatch.rst
@@ -495,6 +495,15 @@ Comments
 
     See: https://lore.kernel.org/lkml/20131006222342.GT19510@leaf/
 
+  **UNCOMMENTED_RGMII_MODE**
+    Historically, the RGMII PHY modes specified in Device Trees have been
+    used inconsistently, often referring to the usage of delays on the PHY
+    side rather than describing the board.
+
+    PHY modes "rgmii", "rgmii-rxid" and "rgmii-txid" modes require the clock
+    signal to be delayed on the PCB; this unusual configuration should be
+    described in a comment. If they are not (meaning that the delay is realized
+    internally in the MAC or PHY), "rgmii-id" is the correct PHY mode.
 
 Commit message
 --------------

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 664f7b7..f597734 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3741,6 +3741,18 @@ sub process {
                        }
                }
 
+# Check for RGMII phy-mode with delay on PCB
+               if ($realfile =~ /\.(dts|dtsi|dtso)$/ &&
+                   $line =~ /^\+\s*(phy-mode|phy-connection-type)\s*=\s*"/ &&
+                   !ctx_has_comment($first_line, $linenr)) {
+                       my $prop = $1;
+                       my $mode = get_quoted_string($line, $rawline);
+                       if ($mode =~ /^"rgmii(?:|-rxid|-txid)"$/) {
+                               WARN("UNCOMMENTED_RGMII_MODE",
+                                    "$prop $mode without comment -- delays on the PCB should be described, otherwise use \"rgmii-id\"\n" . $herecurr);
+                       }
+               }
+
 # check for using SPDX license tag at beginning of files
                if ($realline == $checklicenseline) {
                        if ($rawline =~ /^[ \+]\s*\#\!\s*\//) {