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HAL_Linux: avoiding setting the SPI mode on every transfer 

This was causing the Disco kernel to print a debug message on every
SPI transfer, which makes for a very noisy kernel and large kernel logs
This commit is contained in:
Andrew Tridgell 2016-09-14 18:31:24 +10:00 committed by Lucas De Marchi
parent 19d580d60f
commit a4c1bc3fd3
1 changed files with 30 additions and 5 deletions
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35
libraries/AP_HAL_Linux/SPIDevice.cpp
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@ -162,6 +162,7 @@ public:
uint16_t bus;
uint16_t kernel_cs;
uint8_t ref;
int16_t last_mode = -1;
};
SPIBus::~SPIBus()
@ -275,11 +276,35 @@ bool SPIDevice::transfer(const uint8_t *send, uint32_t send_len,
return false;
}
int r = ioctl(_bus.fd, SPI_IOC_WR_MODE, &_desc.mode);
if (r < 0) {
hal.console->printf("SPIDevice: error on setting mode fd=%d (%s)\n",
_bus.fd, strerror(errno));
return false;
int r;
if (_bus.last_mode == _desc.mode) {
/*
the mode in the kernel is not tied to the file descriptor,
so there is a chance some other process has changed it since
we last used the bus. We want to report when this happens so
the user has a chance of figuring out when there is
conflicted use of the SPI bus. Unfortunately this costs us
an extra syscall per transfer.
*/
uint8_t current_mode;
if (ioctl(_bus.fd, SPI_IOC_RD_MODE, &current_mode) < 0) {
hal.console->printf("SPIDevice: error on getting mode fd=%d (%s)\n",
_bus.fd, strerror(errno));
_bus.last_mode = -1;
} else if (current_mode != _bus.last_mode) {
hal.console->printf("SPIDevice: bus mode conflict fd=%d mode=%u/%u\n",
_bus.fd, (unsigned)_bus.last_mode, (unsigned)current_mode);
_bus.last_mode = -1;
}
}
if (_desc.mode != _bus.last_mode) {
r = ioctl(_bus.fd, SPI_IOC_WR_MODE, &_desc.mode);
if (r < 0) {
hal.console->printf("SPIDevice: error on setting mode fd=%d (%s)\n",
_bus.fd, strerror(errno));
return false;
}
_bus.last_mode = _desc.mode;
}
_cs_assert();