Re: [PATCH] mmc: spi: Toggle SPI polarity, do not hardcode it

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Tue, Dec 10, 2019 at 10:52 AM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> On Wed, 4 Dec 2019 at 16:29, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> >
> > The code in mmc_spi_initsequence() tries to send a burst with
> > high chipselect and for this reason hardcodes the device into
> > SPI_CS_HIGH.
> >
> > This is not good because the SPI_CS_HIGH flag indicates
> > logical "asserted" CS not always the physical level. In
> > some cases the signal is inverted in the GPIO library and
> > in that case SPI_CS_HIGH is already set, and enforcing
> > SPI_CS_HIGH again will actually drive it low.
> >
> > Instead of hard-coding this, toggle the polarity so if the
> > default is LOW it goes high to assert chipselect but if it
> > is already high then toggle it low instead.
> >
> > Cc: Phil Elwell <phil@xxxxxxxxxxxxxxx>
> > Reported-by: Mark Brown <broonie@xxxxxxxxxx>
> > Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
>
> Seems like we should add a stable tag, right?

Yeah I agree.

> In any case, I have applied this for next to let it cook for a while, thanks!

Good, thanks!

Yours,
Linus Walleij



[Index of Archives]     [Linux Memonry Technology]     [Linux USB Devel]     [Linux Media]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux