[PATCH] spi: loopback-test: provide loop_req option.

From: Oleksij Rempel
Date: Fri Jul 14 2017 - 05:42:46 EST


Provide a module parameter to request internal loop by the SPI master
controller.
This should make loop testing easier without extra HW modification.

For test automation a logic analyzer is recommended for host
controller-independent verification.
An example test rig configuration and procedure:
i.MX6S RIoRBoard Logic Analyzer
-----------------------------------------
(J13 4) GND ------------- GND
(J13 6) CSPI3-CLK ------> PIN 3
(J13 8) CSPI3-MOSI <----- PIN 2
^ - internal loop configured by SPI_LOOP
| or can be user external jamper.
(J13 10) CSPI3-MISO -----> PIN 1

grab some data and decode it:
sigrok-cli -d fx2lafw --time 160000 --config samplerate=10m \
--channels 0-2 -o dump.sr
sigrok-cli -i dump.sr -P spi:mosi=1:clk=2 > result_for_regression_tests

Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
drivers/spi/spi-loopback-test.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/drivers/spi/spi-loopback-test.c b/drivers/spi/spi-loopback-test.c
index 3459965004f8..0d3c56e2526c 100644
--- a/drivers/spi/spi-loopback-test.c
+++ b/drivers/spi/spi-loopback-test.c
@@ -51,6 +51,12 @@ MODULE_PARM_DESC(loopback,
"is checked to match tx_buf after the spi_message " \
"is executed");

+int loop_req;
+module_param(loop_req, int, 0);
+MODULE_PARM_DESC(loop_req,
+ "if set controller will be asked to enable test loop mode. " \
+ "If controller supported it, MISO and MOSI will be connected");
+
/* run only a specific test */
int run_only_test = -1;
module_param(run_only_test, int, 0);
@@ -313,6 +319,16 @@ static int spi_loopback_test_probe(struct spi_device *spi)
{
int ret;

+ if (loop_req) {
+ spi->mode = SPI_LOOP | spi->mode;
+ ret = spi_setup(spi);
+ if (ret) {
+ dev_err(&spi->dev, "SPI setup with SPI_LOOP failed (%d)\n",
+ ret);
+ return ret;
+ }
+ }
+
dev_info(&spi->dev, "Executing spi-loopback-tests\n");

ret = spi_test_run_tests(spi, spi_tests);
--
2.13.2