From aa53233a15e22ae207436e4015a69d24f06c2703 Mon Sep 17 00:00:00 2001 From: Simon Glass Date: Wed, 11 Jun 2014 23:29:41 -0600 Subject: Add an I/O tracing feature When debugging drivers it is useful to see what I/O accesses were done and in what order. Even if the individual accesses are of little interest it can be useful to verify that the access pattern is consistent each time an operation is performed. In this case a checksum can be used to characterise the operation of a driver. The checksum can be compared across different runs of the operation to verify that the driver is working properly. In particular, when performing major refactoring of the driver, where the access pattern should not change, the checksum provides assurance that the refactoring work has not broken the driver. Add an I/O tracing feature and associated commands to provide this facility. It works by sneaking into the io.h heder for an architecture and redirecting I/O accesses through its tracing mechanism. For now no commands are provided to examine the trace buffer. The format is fairly simple, so 'md' is a reasonable substitute. Note: The checksum feature is only useful for I/O regions where the contents do not change outside of software control. Where this is not suitable you can fall back to manually comparing the addresses. It might be useful to enhance tracing to only checksum the accesses and not the data read/written. Signed-off-by: Simon Glass --- README | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'README') diff --git a/README b/README index 7129df8..d072370 100644 --- a/README +++ b/README @@ -1000,6 +1000,7 @@ The following options need to be configured: CONFIG_CMD_IMLS List all images found in NOR flash CONFIG_CMD_IMLS_NAND * List all images found in NAND flash CONFIG_CMD_IMMAP * IMMR dump support + CONFIG_CMD_IOTRACE * I/O tracing for debugging CONFIG_CMD_IMPORTENV * import an environment CONFIG_CMD_INI * import data from an ini file into the env CONFIG_CMD_IRQ * irqinfo @@ -1171,6 +1172,28 @@ The following options need to be configured: Note that if the GPIO device uses I2C, then the I2C interface must also be configured. See I2C Support, below. +- I/O tracing: + When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O + accesses and can checksum them or write a list of them out + to memory. See the 'iotrace' command for details. This is + useful for testing device drivers since it can confirm that + the driver behaves the same way before and after a code + change. Currently this is supported on sandbox and arm. To + add support for your architecture, add '#include ' + to the bottom of arch//include/asm/io.h and test. + + Example output from the 'iotrace stats' command is below. + Note that if the trace buffer is exhausted, the checksum will + still continue to operate. + + iotrace is enabled + Start: 10000000 (buffer start address) + Size: 00010000 (buffer size) + Offset: 00000120 (current buffer offset) + Output: 10000120 (start + offset) + Count: 00000018 (number of trace records) + CRC32: 9526fb66 (CRC32 of all trace records) + - Timestamp Support: When CONFIG_TIMESTAMP is selected, the timestamp -- cgit v1.1