Re: [RFC PATCH 1/2] spi: Add support for Zynq QSPI controller
From: Geert Uytterhoeven
Date: Thu Jul 10 2014 - 05:42:14 EST
On Thu, Jul 10, 2014 at 11:31 AM, Harini Katakam
>>> + master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_RX_DUAL | SPI_RX_QUAD |
>>> + SPI_TX_DUAL | SPI_TX_QUAD;
>> Your driver advertises Dual/Quad SPI Transfer capabilities, but it doesn't
>> check spi_transfer.[tr]x_nbits? How can it determine when to enable Dual/Quad?
> Here the driver is just giving information that the controller support it.
> The MTD layer enables dual/quad based on what the flash supports; quad
> being the first priority
> I understand that the spi core reads rx, tx-bus-width property and
> master support flags and
> performs the necessary checks.
That's correct: as long as the rx, tx-bus-width properties do not indicate a
Dual or Quad wiring, it won't be used.
However, based on schematics, someone may set the rx, tx-bus-width properties
to 4, which is correct, as DT describes the hardware. But this will fail to
So I think it's safer not to announce Dual/Quad support in the driver until
the actual driver support is there.
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/