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Following are the major issues in current driver code 1. The current driver simply assumes the transfer completion whenever its gets any non-error interrupts and then simply do the polling of available/free bytes in FIFO. 2. The block mode is not working properly since no handling in being done for OUT_BLOCK_WRITE_REQ and IN_BLOCK_READ_READ. 3. An i2c transfer can contain multiple message and QUP v2 supports reconfiguration during run in which the mode should be same for all the sub transfer. Currently the mode is being programmed before every sub transfer which is functionally wrong. If one message is less than FIFO length and other message is greater than FIFO length, then transfers will fail. Because of above, i2c v2 transfers of size greater than 64 are failing with following error message i2c_qup 78b6000.i2c: timeout for fifo out full To make block mode working properly and move to use the interrupts instead of polling, major code reorganization is required. Following are the major changes done in this patch 1. Remove the polling of TX FIFO free space and RX FIFO available bytes and move to interrupts completely. QUP has QUP_MX_OUTPUT_DONE, QUP_MX_INPUT_DONE, OUT_BLOCK_WRITE_REQ and IN_BLOCK_READ_REQ interrupts to handle FIFO’s properly so check all these interrupts. 2. Determine the mode for transfer before starting by checking all the tx/rx data length in each message. The complete message can be transferred either in DMA mode or Programmed IO by FIFO/Block mode. in DMA mode, both tx and rx uses same mode but in PIO mode, the TX and RX can be in different mode. 3. During write, For FIFO mode, TX FIFO can be directly written without checking for FIFO space. For block mode, the QUP will generate OUT_BLOCK_WRITE_REQ interrupt whenever it has block size of available space. 4. During read, both TX and RX FIFO will be used. TX will be used for writing tags and RX will be used for receiving the data. In QUP, TX and RX can operate in separate mode so configure modes accordingly. 5. For read FIFO mode, wait for QUP_MX_INPUT_DONE interrupt which will be generated after all the bytes have been copied in RX FIFO. For read Block mode, QUP will generate IN_BLOCK_READ_REQ interrupts whenever it has block size of available data. 6. Split the transfer in chunk of one QUP block size(256 bytes) and schedule each block separately. QUP v2 supports reconfiguration during run in which QUP can transfer multiple blocks without issuing a stop events. 7. Port the SMBus block read support for new code changes. Signed-off-by: Abhishek Sahu <absahu@codeaurora.org> Reviewed-by: Sricharan R <sricharan@codeaurora.org> Signed-off-by: Wolfram Sang <wsa@the-dreams.de> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.