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target/armv7m_trace: Improve SWO frequency auto-detection

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The SWO frequency auto-detection with J-Link adapters does not work
properly in the current implementation. This is because the trace layer
has only information about the highest possible SWO frequency supported
by the adapter. With that the trace layer calculates the SWO prescaler
which usually leads to a frequency deviation greater than what is
permitted by J-Link adapters.

Move the calculation of the SWO prescaler from the trace layer into the
trace configuration of the adapter to overcome this problem.
The adapter has the necessary information to choose a suitable SWO
frequency and calculate the corresponding prescaler that complies with
the maximum allowed frequency deviation.

Tested with:
  - STM32L152RC Discovery Kit (ST-Link)
  - EFM32GG-STK3700 (J-Link)

Change-Id: I38ff2b89d32f0a92c597989b590afe5c75cf4902
Signed-off-by: Marc Schink <openocd-dev@marcschink.de>
Reviewed-on: http://openocd.zylin.com/3903
Tested-by: jenkins
Reviewed-by: Paul Fertser <fercerpav@gmail.com>
This commit is contained in:
Marc Schink
2016-12-02 15:39:23 +01:00
committed by Paul Fertser
parent 90bd7d1482
commit 2dc88e1479
8 changed files with 129 additions and 59 deletions
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9
src/jtag/interface.h
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@@ -303,10 +303,14 @@ struct jtag_interface {
* @param trace_freq A pointer to the configured trace
* frequency; if it points to 0, the adapter driver must write
* its maximum supported rate there
* @param traceclkin_freq TRACECLKIN frequency provided to the TPIU in Hz
* @param prescaler Pointer to the SWO prescaler calculated by the
* adapter
* @returns ERROR_OK on success, an error code on failure.
*/
int (*config_trace)(bool enabled, enum tpiu_pin_protocol pin_protocol,
uint32_t port_size, unsigned int *trace_freq);
uint32_t port_size, unsigned int *trace_freq,
unsigned int traceclkin_freq, uint16_t *prescaler);
/**
* Poll for new trace data
@@ -325,7 +329,8 @@ extern const char * const jtag_only[];
void adapter_assert_reset(void);
void adapter_deassert_reset(void);
int adapter_config_trace(bool enabled, enum tpiu_pin_protocol pin_protocol,
uint32_t port_size, unsigned int *trace_freq);
uint32_t port_size, unsigned int *trace_freq,
unsigned int traceclkin_freq, uint16_t *prescaler);
int adapter_poll_trace(uint8_t *buf, size_t *size);
#endif /* OPENOCD_JTAG_INTERFACE_H */