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The omap4 CEC hardware cannot tell a Nack from a Low Drive from an Arbitration Lost error, so just report a Nack, which is almost certainly the reason for the error anyway. This also simplifies the implementation. The only three interrupts that need to be enabled are: Transmit Buffer Full/Empty Change event: triggered when the transmit finished successfully and cleared the buffer. Receiver FIFO Not Empty event: triggered when a message was received. Frame Retransmit Count Exceeded event: triggered when a transmit failed repeatedly, usually due to the message being Nacked. Other reasons are possible (Low Drive, Arbitration Lost) but there is no way to know. If this happens the TX buffer needs to be cleared manually. While testing various error conditions I noticed that the hardware can receive messages up to 18 bytes in total, which exceeds the legal maximum of 16. This could cause a buffer overflow, so we check for this and constrain the size to 16 bytes. The old incorrect interrupt handler could cause the CEC framework to enter into a bad state because it mis-detected the "Start Bit Irregularity event" as an ARB_LOST transmit error when it actually is a receive error which should be ignored. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Reported-by: Henrik Austad <haustad@cisco.com> Tested-by: Henrik Austad <haustad@cisco.com> Tested-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com> |
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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.