Re: AM335x BeagleBone SPI Issues

[Felipe Balbi <balbi@ti.com>]

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Hi again,

On Tue, Dec 11, 2012 at 01:48:10PM +0200, Felipe Balbi wrote:
> On Tue, Dec 11, 2012 at 10:38:58AM +0000, Jack Mitchell wrote:
> > On 11/12/12 10:20, Felipe Balbi wrote:
> > >Hi,
> > >
> > >On Tue, Dec 11, 2012 at 10:17:42AM +0000, Jack Mitchell wrote:
> > >
> > ><big snip>
> > >
> > >>Shubhro, Felipe,
> > >>
> > >>Thank you, the reordering dma patch fixed the dma issue I was having!
> > >>However, the bad news, I now get the same results for the dma and
> > >>non-dma spidev test. While the scope shows the SPI clk and data is
> > >>fine, the reading from the program still shows 0x00 for all words.
> > ><removed spidev_test output>
> > >
> > >>dmesg shows nothing of interest apart from the spi bus setting up.
> > >>Any ideas?
> > >>
> > >>To iterate for my own sanity; I have bridged pins 18 and 21 on the P9
> > >>header which should be the d0 and d1 spi data pins for spi0. This
> > >>result of 0x00 usually comes from a result of not joining the pins,
> > >>but I can assure you they are joined!
> > >>
> > >>Thank you for the help so far.
> > >according to the schematics [1], those pins are muxed as UART2_TXD and
> > >I2C1_SDA, have you remuxed them properly ? Can you try with pins 29 and
> > >30 on the same header ? That's SPI1, so you will have to add DT data for
> > >spidev on that bus too.
> > >
> > >[1] http://beagleboard.org/static/beaglebone/latest/Docs/Hardware/BONE_SCH.pdf
> > >
> > 
> > No change unfortunately:
> > 
> > root@beaglebone:~# ./spidev
> > spi mode: 0
> > bits per word: 16
> > max speed: 24000000 Hz (24000 KHz)
> > 
> > 00 00 00 00 00 00
> > 00 00 00 00 00 00
> > 00 00 00 00 00 00
> > 00 00 00 00 00 00
> > 00 00 00 00 00 00
> > 00 00 00 00 00 00
> > 00 00
> > 
> > root@beaglebone:~# ./spidev -D /dev/s
> > shm/       spidev1.0  spidev2.0  stderr     stdin      stdout
> > root@beaglebone:~# ./spidev -D /dev/spidev2.0

one thing caught my attention, shouldn't you be passing '-l' argument
here for loopback testing ? That would mean you need to make sure your
"spi->mode" has SPI_LOOP flag set. Currently there is no way to do that
via DeviceTree (AFAICT), so please apply ths patch to your tree and set
spi-loopback; property for your spidev entry:

diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
index 296015e..1949586 100644
--- a/Documentation/devicetree/bindings/spi/spi-bus.txt
+++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
@@ -55,6 +55,8 @@ contain the following properties.
     		chip select active high
 - spi-3wire       - (optional) Empty property indicating device requires
     		    3-wire mode.
+- spi-loopback    - (optional) Empty property indicating device requires
+    		    loopback mode.
 
 If a gpio chipselect is used for the SPI slave the gpio number will be passed
 via the cs_gpio
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 3f1b9ee..6bcdc03 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -868,6 +868,8 @@ static void of_register_spi_devices(struct spi_master *master)
 			spi->mode |= SPI_CS_HIGH;
 		if (of_find_property(nc, "spi-3wire", NULL))
 			spi->mode |= SPI_3WIRE;
+		if (of_find_property(nc, "spi-loopback", NULL))
+			spi->mode |= SPI_LOOP;
 
 		/* Device speed */
 		prop = of_get_property(nc, "spi-max-frequency", &len);

-- 
balbi

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