Re: [PATCH RFC 1/3] spi: Allow SPI controller override device buswidth

Sergei Shtylyov
2020-03-01T10:04:07Z

Hello!

On 28.02.2020 18:18, John Garry wrote:

> Currently ACPI firmware description for a SPI device does not have any
> method to describe the data buswidth on the board.
>
> So even through the controller and device may support higher modes than
^^^^^^^
Though?

> standard SPI, it cannot be assumed that the board does - as such, that
> device is limited to standard SPI in such a circumstance.
>
> As a workaround, allow the controller driver supply buswidth override bits,
> which are used inform the core code that the controller driver knows the
> buswidth supported on that board for that device.
>
> A host controller driver might know this info from DMI tables, for example.
>
> Signed-off-by: John Garry <john.garry-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
> ---
> drivers/spi/spi.c | 4 +++-
> include/linux/spi/spi.h | 3 +++
> 2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 38b4c78df506..292f26807b41 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -510,6 +510,7 @@ struct spi_device *spi_alloc_device(struct spi_controller *ctlr)
> spi->dev.bus = &spi_bus_type;
> spi->dev.release = spidev_release;
> spi->cs_gpio = -ENOENT;
> + spi->mode = ctlr->buswidth_override_bits;
>
> spin_lock_init(&spi->statistics.lock);
>
> @@ -2181,9 +2182,10 @@ static acpi_status acpi_register_spi_device(struct spi_controller *ctlr,
> return AE_NO_MEMORY;
> }
>
> +

What for?

> ACPI_COMPANION_SET(&spi->dev, adev);
> spi->max_speed_hz = lookup.max_speed_hz;
> - spi->mode = lookup.mode;
> + spi->mode |= lookup.mode;
> spi->irq = lookup.irq;
> spi->bits_per_word = lookup.bits_per_word;
> spi->chip_select = lookup.chip_select;
[...]

MBR, Sergei