From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753361AbdBAQ5A (ORCPT ); Wed, 1 Feb 2017 11:57:00 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:47380 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752858AbdBAQ44 (ORCPT ); Wed, 1 Feb 2017 11:56:56 -0500 From: Christopher Bostic To: robh+dt@kernel.org, mark.rutland@arm.com, linux@armlinux.org.uk, gregkh@linuxfoundation.org, mturquette@baylibre.com, geert+renesas@glider.be, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, joel@jms.id.au, linux-kernel@vger.kernel.org, andrew@aj.id.au, alistair@popple.id.au, benh@kernel.crashing.org Cc: Chris Bostic Subject: [PATCH v3 15/18] drivers/fsi: Add FSI bus documentation Date: Wed, 1 Feb 2017 10:53:55 -0600 X-Mailer: git-send-email 2.10.1 (Apple Git-78) In-Reply-To: <20170201165358.45415-1-cbostic@linux.vnet.ibm.com> References: <20170201165358.45415-1-cbostic@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17020116-0040-0000-0000-000002852F0C X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006537; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000201; SDB=6.00815769; UDB=6.00398295; IPR=6.00593211; BA=6.00005108; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00014138; XFM=3.00000011; UTC=2017-02-01 16:56:54 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17020116-0041-0000-0000-000006783878 Message-Id: <20170201165358.45415-16-cbostic@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-02-01_13:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1702010167 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Chris Bostic Add details on the basic functions of the FSI serial bus. Signed-off-by: Chris Bostic --- Documentation/devicetree/bindings/fsi/fsi.txt | 54 +++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 Documentation/devicetree/bindings/fsi/fsi.txt diff --git a/Documentation/devicetree/bindings/fsi/fsi.txt b/Documentation/devicetree/bindings/fsi/fsi.txt new file mode 100644 index 0000000..7fa2394 --- /dev/null +++ b/Documentation/devicetree/bindings/fsi/fsi.txt @@ -0,0 +1,54 @@ +FSI: Flexible Support processor Interface + +FSI is a two line serial bus capable of running at speeds up to 166 MHz. +The lines consist of a clock responsible for synchronizing the target device +(slave) with the master which is responsible for all transactions on the bus. +The master owns the clock line and is the only side allowed to change its +state. The second line, SDA, is a data line that conveys information to/from +the slave who samples based on the clock line. The data line is +bi-directional. + +The master initiates communication by sending a command to the slave and +depending on the type of command will allow the slave to control the bus +to return requested data. All commands are CRC protected. The slave upon +receipt of a command will determine if the CRC is correct and discard +the data if noise has corrupted the line. In the same manner the master +will verify the CRC received from the slave. + +Types of commands: +Read 32 bit: Read a 32 bit word from a specified address on the slave. +Read 16 bit: Read a 16 bit 'half word' from a specified address on the slave. +read 8 bit: Read a byte from a specified address on the slave. +Write 32,16,8 bit: Write to a specified address on the slave with the provided + data. +BREAK: Initialize the slave's logic to receive commands. +TERM: Terminate the slave's error lockout to resume communications + after an error on the bus is detected. +D-POLL: Poll the slave to determine when it is no longer buy processing + a previous command. +I-POLL: Interrupt signal check. Master queries slave to see if any + interrupts are asserting. + +High fanout capability: +FSI buses can be chained together in 'hub' configurations to expand the +available communications channels and thus allow connetion to more slaves. + + +Typical implementation + + FSI master ----- slave with local FSI master (hub) ------- downstream slave + + +Each two line combination of a clock and data line is collectively referred +to as a 'FSI link'. Depending on hardware the primary FSI master may support +up to 64 links. Hub FSI masters can support at most 8 links. Total number +of supported slaves can grow exponentially depending on how many hubs are +placed in the path. Presently only two hubs in the chain are allowed but +in the future this may be expanded. + +The slave hardware logic responsible for decoding FSI master commands is +contained in a CFAM (Common Field replaceable unit Access Macro). Up to +4 slaves or CFAMs can be connected on each FSI link. CFAMs in addition +to the slave logic (or engine) can contain other functions that allow access +via FSI. Common additional functionality includes I2C masters, GPIO +controllers, UARTs, etc... -- 1.8.2.2