unimore/kernel-hacking-2024-linux-steffo
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Linux kernel modifications for the Kernel Hacking exam
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Corinna Vinschen 5d54cb1767 igb: conditionalize I2C bit banging on external thermal sensor support 
Commit a97f8783a9 ("igb: unbreak I2C bit-banging on i350") introduced
code to change I2C settings to bit banging unconditionally.

However, this patch introduced a regression:  On an Intel S2600CWR
Server Board with three NICs:

- 1x dual-port copper
  Intel I350 Gigabit Network Connection [8086:1521] (rev 01)
  fw 1.63, 0x80000dda

- 2x quad-port SFP+ with copper SFP Avago ABCU-5700RZ
  Intel I350 Gigabit Fiber Network Connection [8086:1522] (rev 01)
  fw 1.52.0

the SFP NICs no longer get link at all.  Reverting commit a97f8783a9
or switching to the Intel out-of-tree driver both fix the problem.

Per the igb out-of-tree driver, I2C bit banging on i350 depends on
support for an external thermal sensor (ETS).  However, commit
a97f8783a9 added bit banging unconditionally.  Additionally, the
out-of-tree driver always calls init_thermal_sensor_thresh on probe,
while our driver only calls init_thermal_sensor_thresh only in
igb_reset(), and only if an ETS is present, ignoring the internal
thermal sensor.  The affected SFPs don't provide an ETS.  Per Intel,
the behaviour is a result of i350 firmware requirements.

This patch fixes the problem by aligning the behaviour to the
out-of-tree driver:

- split igb_init_i2c() into two functions:
  - igb_init_i2c() only performs the basic I2C initialization.
  - igb_set_i2c_bb() makes sure that E1000_CTRL_I2C_ENA is set
    and enables bit-banging.

- igb_probe() only calls igb_set_i2c_bb() if an ETS is present.

- igb_probe() calls init_thermal_sensor_thresh() unconditionally.

- igb_reset() aligns its behaviour to igb_probe(), i. e., call
  igb_set_i2c_bb() if an ETS is present and call
  init_thermal_sensor_thresh() unconditionally.

Fixes: a97f8783a9 ("igb: unbreak I2C bit-banging on i350")
Tested-by: Mateusz Palczewski <mateusz.palczewski@intel.com>
Co-developed-by: Jamie Bainbridge <jbainbri@redhat.com>
Signed-off-by: Jamie Bainbridge <jbainbri@redhat.com>
Signed-off-by: Corinna Vinschen <vinschen@redhat.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://lore.kernel.org/r/20230214185549.1306522-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-02-15 21:20:40 -08:00
arch - Prevent the compiler from reordering accesses to debug regs which could cause 2023-02-05 11:28:42 -08:00
block block-6.2-2023-02-03 2023-02-03 11:35:42 -08:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-01-31 17:53:01 +09:00
crypto This update includes the following changes: 2022-12-14 12:31:09 -08:00
Documentation Networking fixes for 6.2-rc8, including fixes from can and 2023-02-09 09:17:38 -08:00
drivers igb: conditionalize I2C bit banging on external thermal sensor support 2023-02-15 21:20:40 -08:00
fs small fix for use after free 2023-02-09 09:00:26 -08:00
include dccp/tcp: Avoid negative sk_forward_alloc by ipv6_pinfo.pktoptions. 2023-02-10 19:53:42 -08:00
init Kbuild fixes for v6.2 (3rd) 2023-01-21 10:56:37 -08:00
io_uring io_uring: always prep_async for drain requests 2023-01-27 06:29:29 -07:00
ipc Non-MM patches for 6.2-rc1. 2022-12-12 17:28:58 -08:00
kernel Fix regression in poll() and select() 2023-02-07 07:54:40 -08:00
lib - Lock the proper critical section when dealing with perf event context 2023-02-05 11:03:56 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm 25 hotfixes, mainly for MM. 13 are cc:stable. 2023-02-03 10:01:57 -08:00
net net: mpls: fix stale pointer if allocation fails during device rename 2023-02-15 10:26:37 +00:00
rust rust: print: avoid evaluating arguments in pr_* macros in unsafe blocks 2023-01-16 00:54:35 +01:00
samples ftrace: Export ftrace_free_filter() to modules 2023-01-24 11:20:58 -05:00
scripts Kbuild fixes for v6.2 (4th) 2023-02-04 11:30:23 -08:00
security tomoyo: Update website link 2023-01-13 23:11:38 +09:00
sound sound fixes for 6.2-rc7 2023-02-01 10:26:23 -08:00
tools selftests: fib_rule_tests: Test UDP and TCP connections with DSCP rules. 2023-02-09 22:49:04 -08:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt VFIO fixes for v6.2-rc6 2023-01-23 11:56:07 -08:00
.clang-format iommufd for 6.2 2022-12-14 09:15:43 -08:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes
.gitignore .gitignore: ignore *.rpm 2022-12-30 17:22:14 +09:00
.mailmap 25 hotfixes, mainly for MM. 13 are cc:stable. 2023-02-03 10:01:57 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS MAINTAINERS: update SCTP maintainers 2023-02-02 11:35:33 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS USB fixes for 6.2-rc7 2023-02-05 12:19:55 -08:00
Makefile Linux 6.2-rc7 2023-02-05 13:13:28 -08:00
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README 

Linux kernel
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Please read the Documentation/process/changes.rst file, as it contains the
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