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Jarkko Nikula c42edde5de i2c: designware: Fix slave state machine for sequential reads 
Some read types from I2C bus don't work correctly when testing the
i2c-designware-slave.c with the slave-eeprom backend. The same reads
work correctly when testing with a real 24c02 EEPROM chip.

In the following tests an i2c-designware-slave.c instance with the
slave-eeprom backend is configured to act as a simulated 24c02 at
address 0x65 on an I2C host bus 6:

1. i2cdump -y 6 0x65 b (OK)
   Random read. Each byte are read using a byte address write with a
   current address read in a same message.
2. i2cdump -y 6 0x65 c (OK, was NOK before commit 3b5f7f10ff when it
                        was repeating the 1st byte)
   Repeated current address read. One byte address write message
   followed by repeated current address read messages.
3. i2cdump -y 6 0x65 i (NOK, each 32 byte block repeats the 1st byte of
                        block)
   Sequential read using SMBus Block Read. For each 32 byte block a byte
   address write followed by 32 sequental reads in a same message.

These findings are explained because the implementation has had a
mismatch between hardware interrupts and what I2C slave events should be
sent after those interrupts. Despite that the case 1 happened to have
always the I2C slave events sent to a right order with a right data
between backend and the I2C bus.

Hardware generates the DW_IC_INTR_RD_REQ interrupt when another host is
attempting to read and for sequential reads after. DW_IC_INTR_RX_DONE
occurs when host does not acknowledge a transmitted byte which is an
indication the end of transmission.

Those interrupts do not match directly with I2C_SLAVE_READ_REQUESTED and
I2C_SLAVE_READ_PROCESSED events which is how the code was and is
practically using them. The slave-eeprom backend increases the buffer
index with the I2C_SLAVE_READ_PROCESSED event and returns the data from
current index when receiving only the I2C_SLAVE_READ_REQUESTED event.

That explains the repeated bytes in case 3 and also case 2 before
commit 3b5f7f10ff ("i2c: designware: slave should do WRITE_REQUESTED
before WRITE_RECEIVED").

Patch fixes the case 3 while keep cases 1 and 2 working with following
changes:

- First DW_IC_INTR_RD_REQ interrupt will change the state machine to
  read in progress state, send I2C_SLAVE_READ_REQUESTED event and
  transmit the first byte from backend
- Subsequent DW_IC_INTR_RD_REQ interrupts will send
  I2C_SLAVE_READ_PROCESSED events and transmit next bytes from backend
- STOP won't change the state machine. Otherwise case 2 won't work since
  we cannot distinguish current address read from sequentiel read
- DW_IC_INTR_RX_DONE interrupt is needless since there is no mechanism
  to inform it to a backend. It cannot be used to change state machine
  at the end of read either due the same reason than above
- Next host write to us will change the state machine from read to write
  in progress state
- STATUS_WRITE_IN_PROGRESS and STATUS_READ_IN_PROGRESS are considered
  now to be status flags not the state of the driver. This is how we
  treat them in i2c-designware-master.c

While at it do not test the return code from i2c_slave_event() for
I2C_SLAVE_READ_REQUESTED and I2C_SLAVE_READ_PROCESSED since it returns
always 0.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
2022-11-12 07:37:17 +01:00
arch - Rename a perf memory level event define to denote it is of CXL type 2022-10-30 09:49:18 -07:00
block block-6.1-2022-10-28 2022-10-29 18:06:52 -07:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto treewide: use get_random_bytes() when possible 2022-10-11 17:42:58 -06:00
Documentation dt-bindings: i2c: add entry for hisilicon,ascend910-i2c 2022-11-02 21:23:52 +01:00
drivers i2c: designware: Fix slave state machine for sequential reads 2022-11-12 07:37:17 +01:00
fs 3 cifs/smb3 fixes (also for stable) 2022-10-30 09:40:04 -07:00
include fbdev fixes for kernel 6.1-rc3: 2022-10-30 11:31:14 -07:00
init init: Kconfig: fix spelling mistake "satify" -> "satisfy" 2022-10-20 21:27:22 -07:00
io_uring io_uring: unlock if __io_run_local_work locked inside 2022-10-27 09:52:12 -06:00
ipc ipc/msg.c: fix percpu_counter use after free 2022-10-28 13:37:22 -07:00
kernel - Rename a perf memory level event define to denote it is of CXL type 2022-10-30 09:49:18 -07:00
lib 23 hotfixes. 2022-10-29 17:49:33 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mmap: fix remap_file_pages() regression 2022-10-28 13:37:23 -07:00
net kcm: do not sense pfmemalloc status in kcm_sendpage() 2022-10-27 11:25:13 -07:00
rust Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
samples VFIO updates for v6.1-rc1 2022-10-12 14:46:48 -07:00
scripts Kbuild fixes for v6.1 2022-10-16 11:12:22 -07:00
security selinux: enable use of both GFP_KERNEL and GFP_ATOMIC in convert_context() 2022-10-19 09:55:53 -04:00
sound ALSA: aoa: Fix I2S device accounting 2022-10-27 08:53:08 +02:00
tools Char/Misc fixes for 6.1-rc3 2022-10-30 11:22:33 -07:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt kvm: Add support for arch compat vm ioctls 2022-10-22 05:15:23 -04:00
.clang-format PCI/DOE: Add DOE mailbox support functions 2022-07-19 15:38:04 -07:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap mailmap: update email for Qais Yousef 2022-10-20 21:27:21 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS drm for 5.20/6.0 2022-08-03 19:52:08 -07:00
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 dt-bindings: i2c: add entry for hisilicon,ascend910-i2c 2022-11-02 21:23:52 +01:00
Makefile Linux 6.1-rc3 2022-10-30 15:19:28 -07:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.