[src/trunk]: src/sys/external/bsd/drm2/linux linux: Repeat i2c transfer if dr...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/aff538227dc1
branches:  trunk
changeset: 366352:aff538227dc1
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun May 22 18:41:14 2022 +0000

description:
linux: Repeat i2c transfer if driver fails with EAGAIN.

The Intel GMBUS (graphics management bus, i2c controller) relies on
this now to fall back from interrupt-driven xfers to bit-banging.

diffstat:

 sys/external/bsd/drm2/linux/linux_i2c.c |  16 +++++++++++++---
 1 files changed, 13 insertions(+), 3 deletions(-)

diffs (38 lines):

diff -r 4ce24bd92b7f -r aff538227dc1 sys/external/bsd/drm2/linux/linux_i2c.c
--- a/sys/external/bsd/drm2/linux/linux_i2c.c   Sun May 22 17:55:08 2022 +0000
+++ b/sys/external/bsd/drm2/linux/linux_i2c.c   Sun May 22 18:41:14 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux_i2c.c,v 1.6 2021/12/19 11:49:12 riastradh Exp $  */
+/*     $NetBSD: linux_i2c.c,v 1.7 2022/05/22 18:41:14 riastradh Exp $  */
 
 /*-
  * Copyright (c) 2015 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_i2c.c,v 1.6 2021/12/19 11:49:12 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_i2c.c,v 1.7 2022/05/22 18:41:14 riastradh Exp $");
 
 #include <sys/types.h>
 #include <sys/errno.h>
@@ -127,8 +127,18 @@
 int
 __i2c_transfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int n)
 {
+       unsigned timeout = hz;  /* XXX adapter->timeout */
+       unsigned start = getticks();
+       int ret, nretries = 0;
 
-       return (*adapter->algo->master_xfer)(adapter, msgs, n);
+       do {
+               ret = (*adapter->algo->master_xfer)(adapter, msgs, n);
+               if (ret != -EAGAIN)
+                       break;
+       } while (nretries++ < adapter->retries &&
+           getticks() - start < timeout);
+
+       return ret;
 }
 
 int