mpt
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Target driver for LSI/MPT XXX cards =================================== Version X.X.X, XX XXX 200X -------------------------- This driver was originally developed by Hu Gang and then is developed by Erik Habbinga <[email protected]>. It is on the early stage of development. The current maintainer of this driver is Erik. Please send him all question related to it (CC: [email protected]). Building from the Linux kernel tree ----------------------------------- To build from the kernel tree, you should: 1. Link drivers/message/fusion/mpt_scst to $(SCST_DIR)/mpt. 2. Copy or link Makefile and Kconfig from $(SCST_DIR)/mpt/in-tree to $(SCST_DIR)/mpt (Makefile will be replaced). 3. Patch drivers/message/fusion/Makefile and drivers/message/fusion/Kconfig by diffs from $(SCST_DIR)/mpt/in-tree 4. Correct in drivers/message/fusion/Makefile SCST_INC_DIR variable so it points to correct directory with SCST include files. Building outside the Linux kernel tree -------------------------------------- Edit Makefile, comment there line obj-$(CONFIG_FUSION_SCST) += mpt_scst.o and uncomment line obj-m += mpt_scst.o Notes on implementation ----------------------- The driver takes the mptstm target driver implemented by LSI and ports it to the SCST architecture. The LSI hardware returns an error when it realizes that command status and sense data cannot be sent in the same transaction. This happens during non-packetized SCSI command handling (not FC or SAS). For SCSI implementations, the driver speculatively caches sense data. If the hardware reports that the sense data could not be sent, the driver will return the cached sense data without involving SCST if the next command is REQUEST SENSE. Cached sense data is discarded on bus reset or if the next command after sense send failure was not REQUEST SENSE. Caching sense data in this fashion probably won't work in a tagged command queuing environment. If SCSI hardware is being used, the driver inspects responses to the INQUIRY command and clears the BQUE and CMDQUE bits in the standard INQUIRY response to disable tagged command queuing. Known issues ------------ Newer versions of SCSI HBA firmware have a bug where the incorrect amount of data is transferred for non-divisible-by-4 length transfers (like standard 14 byte REQUEST SENSE). It's hit or miss for recently bought cards if it has bad firmware or not. Some recently acquired PCIe SCSI HBA had a mix of good and bad target firmware. Revision 1.03.29 is where it broke, and all the target firmware on LSI's website is 1.03.34, which is broken for target mode. As a workaround the SCSI parallel transfer rate is forced to very slow asynchronous wide (Fast-5), which doesn't quite hit >> 10 MB/sec, depending on the SCSI HBA firmware revision. LSI is aware of the problem and the driver will be updated to restore functionality upon a new good SCSI HBA firmware release.