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

[John Garry]

On 01/03/2020 10:04, Sergei Shtylyov wrote:
> Hello!

Hi Sergei,

> 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
>  ÂÂÂÂÂÂÂÂÂ ^^^^^^^
>  ÂÂ Though?

right

> > 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@xxxxxxxxxx>
> > ---
> > Â drivers/spi/spi.cÂÂÂÂÂÂ | 4 +++-
> > Â include/linux/spi/spi.h | 3 +++
> > Â 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)
> > ÂÂÂÂÂ spi->dev.bus = &spi_bus_type;
> > ÂÂÂÂÂ spi->dev.release = spidev_release;
> > ÂÂÂÂÂ spi->cs_gpio = -ENOENT;
> > +ÂÂÂ spi->mode = ctlr->buswidth_override_bits;
> > ÂÂÂÂÂ spin_lock_init(&spi->statistics.lock);
> > @@ -2181,9 +2182,10 @@ static acpi_status 
> > acpi_register_spi_device(struct spi_controller *ctlr,
> > ÂÂÂÂÂÂÂÂÂ return AE_NO_MEMORY;
> > ÂÂÂÂÂ }
> > +
>
>  ÂÂ What for?

slipped through the net

> > ÂÂÂÂÂ ACPI_COMPANION_SET(&spi->dev, adev);
> > ÂÂÂÂÂ spi->max_speed_hzÂÂÂ = lookup.max_speed_hz;
> > -ÂÂÂ spi->modeÂÂÂÂÂÂÂ = lookup.mode;
> > +ÂÂÂ spi->modeÂÂÂÂÂÂÂ |= lookup.mode;
> > ÂÂÂÂÂ spi->irqÂÂÂÂÂÂÂ = lookup.irq;
> > ÂÂÂÂÂ spi->bits_per_wordÂÂÂ = lookup.bits_per_word;
> > ÂÂÂÂÂ spi->chip_selectÂÂÂ = lookup.chip_select;
> [...]

TBH, I did not think that this series would be applied since I tagged it 
as RFC, hence the typos which would have been caught. Indeed, this also 
exposes an issue with enabling quad SPI for a spansion SPI NOR part, 
which I need to debug now in the SPI NOR driver.

Hi Mark,

Do you want me to do anything about the above superfluous newline?

Thanks,
John

> MBR, Sergei
>
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