On 04/06/2015 11:45 PM, Martin Sperl wrote:
On 07.04.2015, at 05:01, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote:
I believe the bcm283x have 2 types of SPI controller. There is 1
instance of the HW that this driver controls (SPI0), and that has CS0,
CS1. There are two instances of a different SPI HW block (SPI1, SPI2),
and those each have CS0, CS1, CS2. At least, that's my interpretation of
the table that shows the pinctrl module's per-pin alternate function values.
Yes and no - SPI1 and SPI2 are a totally different beasts as these are
"auxiliar devices" that have 2x2 word fifos, no DMA and minimal interrupt
support and use a distinct register layout compared to SPI0.
See BCM2835 Arm Peripherials page 20-27 for details.
Essentially these are intended to get used for low speed devices or devices
that run short transfers (<4-8 bytes)
So these devices would need a totally separate SPI driver, which this driver
does not and can not handle...
That's exactly what I said.
Should that be an error? Not being able to find the gpiochip implies the
code can't manipulate the CS lines at all, I think?
>
Will add an dev_warn_once and contine without optimizations - the code
still does check for the cs_gpio, so we would run without it?
It could just be a rename of the pinctrl driver that would trigger this.
You want it as an error?
If the rest of the driver is expected to always check whether
spi->cs_gpio is valid or not, and support the gpio-is-not-valid case, I
guess it's OK for that case *not* to error out.
I think we should at least warn to indicate that something unexpected
happened.
Shouldn't spi->cs_gpio be set to e.g. -1 if the pinctrl device can't be
found, so that the rest of the driver does know that the GPIO is invalid?
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