{"id":2229273,"url":"http://patchwork.ozlabs.org/api/1.1/covers/2229273/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-i2c/cover/20260427-i2c-xiic-v1-0-e6207f9aa5ad@nexthop.ai/","project":{"id":35,"url":"http://patchwork.ozlabs.org/api/1.1/projects/35/?format=json","name":"Linux I2C development","link_name":"linux-i2c","list_id":"linux-i2c.vger.kernel.org","list_email":"linux-i2c@vger.kernel.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260427-i2c-xiic-v1-0-e6207f9aa5ad@nexthop.ai>","date":"2026-04-28T00:18:05","name":"[0/3] i2c: xiic: fix SMBus block read and PEC support","submitter":{"id":92480,"url":"http://patchwork.ozlabs.org/api/1.1/people/92480/?format=json","name":"Abdurrahman Hussain via B4 Relay","email":"devnull+abdurrahman.nexthop.ai@kernel.org"},"mbox":"http://patchwork.ozlabs.org/project/linux-i2c/cover/20260427-i2c-xiic-v1-0-e6207f9aa5ad@nexthop.ai/mbox/","series":[{"id":501748,"url":"http://patchwork.ozlabs.org/api/1.1/series/501748/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-i2c/list/?series=501748","date":"2026-04-28T00:18:06","name":"i2c: xiic: fix SMBus block read and PEC support","version":1,"mbox":"http://patchwork.ozlabs.org/series/501748/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/covers/2229273/comments/","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-i2c@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=Ou9HWgAW;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c04:e001:36c::12fc:5321; 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charset=\"utf-8\"","Content-Transfer-Encoding":"7bit","X-B4-Tracking":"v=1; b=H4sIAL3872kC/yXMSwqAMAxF0a1IxhZq8ANuRRzUGDUOqrQqQuner\n To8cN8L4NkJe2izAI4v8bLZhCLPgBZjZ1YyJgNqrHWJjRIkdYuQQsNDpQsmjQZSvjue5P6uuv6\n 3P4eV6Xj3EOMD+w3U4mwAAAA=","X-Change-ID":"20260427-i2c-xiic-2aeb501ec02a","To":"Michal Simek , Andi Shyti ","Cc":"linux-arm-kernel@lists.infradead.org, linux-i2c@vger.kernel.org,\n linux-kernel@vger.kernel.org, Abdurrahman Hussain ","X-Mailer":"b4 0.15.1","X-Developer-Signature":"v=1; a=openpgp-sha256; l=2226;\n i=abdurrahman@nexthop.ai; h=from:subject:message-id;\n bh=CsiHZ5vb7Sf7aVyvtEGZ7+CNeUx8W/SFG7JbsXLjEQE=;\n b=owJ4nJvAy8zAJbYltPXv6rsCXxhPqyUxZL7/c1CCcemG8lNB+zimTlrSqKJ59d31H1dZVm4w5\n 98clSr9LMigo5SFQYyLQVZMkWXOI/83bR1tERtiDtnDzGFlAhnCwMUpABOZspaRYfvjn5c6/q7r\n K/zJrHWW7Wi07ZYaD+d7W91UKkJ+MvtfMWBkuPRz4joViehXlfpOOT+yFizSF1rYPEfR2m31H6k\n rynYrmQAl5VAE","X-Developer-Key":"i=abdurrahman@nexthop.ai; a=openpgp;\n fpr=9CE24FEC86888658B05CC23FB45585FDABDD10F4","X-Endpoint-Received":"by B4 Relay for abdurrahman@nexthop.ai/default with\n auth_id=756","X-Original-From":"Abdurrahman Hussain ","Reply-To":"abdurrahman@nexthop.ai"},"content":"This series fixes three independent bugs in the Xilinx AXI IIC driver\nthat together make SMBus block reads with PEC return -EBADMSG or -EIO\non otherwise clean transfers. They only surface when the client has\nI2C_CLIENT_PEC set; non-PEC block reads happen to mask each issue in\nturn.\n\nThe problems were uncovered driving an adm1266 PMBus device behind a\nXilinx AXI IIC FPGA block and reading its 64-byte blackbox record.\n\nPatch 1 stops xiic_smbus_block_read_setup() from truncating rx_msg->len.\nThe i2c core appends a byte to msg->len when PEC is enabled, so\noverwriting the length to \"block size + 1\" silently drops the PEC byte\nand i2c_smbus_check_pec() then reads the last payload byte as the PEC.\n\nPatch 2 raises the RX_FULL threshold so the interrupt only fires once\nevery remaining byte (payload plus optional PEC) is already buffered in\nthe FIFO. The previous threshold of rxmsg_len - 2 caused the\nbytes_rem == 1 path in xiic_read_rx() to NACK a byte still on the wire.\n\nPatch 3 stops the BNB handler from forcing tx_msg->len = 1 to signal\ncompletion. tx_msg and rx_msg alias the same i2c_msg during a receive,\nso this also clobbered rx_msg->len; and because tx_pos is already at 2\nin the PEC case, the unsigned subtraction in xiic_tx_space() underflowed\nand the STATE_DONE check fell through to STATE_ERROR. Advancing tx_pos\nup to msg->len drives tx_space to zero without touching the length.\n\nAll three patches are pure bug fixes; non-PEC behaviour is unchanged.\nTested on real hardware -- a Xilinx AXI IIC controller talking to an\nadm1266, where 64-byte PEC-checked block reads now complete cleanly.\n\nSigned-off-by: Abdurrahman Hussain \n---\nAbdurrahman Hussain (3):\n i2c: xiic: preserve PEC byte length in SMBus block read setup\n i2c: xiic: defer RX_FULL until all trailing bytes are in FIFO\n i2c: xiic: don't clobber msg->len to signal block-read completion\n\n drivers/i2c/busses/i2c-xiic.c | 20 +++++++++++---------\n 1 file changed, 11 insertions(+), 9 deletions(-)\n---\nbase-commit: 254f49634ee16a731174d2ae34bc50bd5f45e731\nchange-id: 20260427-i2c-xiic-2aeb501ec02a\n\nBest regards,\n-- \nAbdurrahman Hussain "}