On 10/10/2016 09:34 PM, Stephen Warren wrote:
> On 10/07/2016 05:33 PM, Ralf Ramsauer wrote:
>> Hi Stephen,
>>
>> On 10/07/2016 08:33 PM, Stephen Warren wrote:
>>> On 10/07/2016 07:25 AM, Ralf Ramsauer wrote:
>>>> Hi,
>>>>
>>>> I'm running a Jetson TK1 on mainline Linux. To enable userspace SPI, I
>>>> modified the device-tree by:
>>>>
>>>> /* Expansion TS_SPI_* */
>>>> spi@7000d400 {
>>>> status = "okay";
>>>> + spidev@0 {
>>>> + compatible = "spidev";
>>>> + reg = <0>;
>>>> + spi-max-frequency = <25000000>;
>>>> + };
>>>> };
>>>>
>>>> This works fine. Is it possible to use arbitrary GPIOs as additional
>>>> chip-selects?
>>>>
>>>> What would I have to do If I'd like to add PU0 or PU1 (sysfs
>>>> gpio160/161) as chip-selects?
>>>
>>> According to Documentation/devicetree/bindings/spi/spi-bus.txt, there
>>> are standard properties you can use for GPIO chip-select signals, and it
>>> looks like the SPI core code handles this itself. However, judging by a
>> Yes, I already followed those instructions and it didn't work. Other CSs
>> seem to be ignored, without any warnings while the native CS line still
>> keeps working. That's why I came up with this post. Adding a line to the
>> DT like
>>
>> cs-gpios = <0>, <&gpio TEGRA_GPIO(X, Y) GPIO_ACTIVE_LOW>;
>>
>> should actually (at least syntactically and semantically) be fine for an
>> additional CS, right?
>
> I don't think you can mix non-GPIO and GPIO-based CS lines; I'd expect
> either no cs-gpios property (to use purely HW CS lines), or a cs-gpios
> property that contained an entry for every valid CS line, all as GPIOs.
According to Documentation/devicetree/bindings/spi/spi-bus.txt you can
and the driver *should* support it:
[snip]
So if for example the controller has 2 CS lines, and the cs-gpios
property looks like this:
cs-gpios = <&gpio1 0 0> <0> <&gpio1 1 0> <&gpio1 2 0>;
Then it should be configured so that num_chipselect = 4 with the
following mapping:
cs0 : &gpio1 0 0
cs1 : native
cs2 : &gpio1 1 0
cs3 : &gpio1 2 0
[/snip]
But I'll give it a try using GPIO-based CS lines only, maybe this works.
Ralf
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