On Thu, 25 May 2023 14:05:35 +0300 (EEST)
Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> wrote:
> On Thu, 25 May 2023, Hugo Villeneuve wrote:
>
> > From: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
> >
> > Make sure we wait at least 3us before initiating communication with
> > the device after reset.
> >
> > Signed-off-by: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
> > ---
> > drivers/tty/serial/sc16is7xx.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> > index a7c4da3cfd2b..af7e66db54b4 100644
> > --- a/drivers/tty/serial/sc16is7xx.c
> > +++ b/drivers/tty/serial/sc16is7xx.c
> > @@ -1428,6 +1428,12 @@ static int sc16is7xx_probe(struct device *dev,
> > regmap_write(s->regmap, SC16IS7XX_IOCONTROL_REG << SC16IS7XX_REG_SHIFT,
> > SC16IS7XX_IOCONTROL_SRESET_BIT);
> >
> > + /*
> > + * After reset, the host must wait at least 3us before initializing a
> > + * communication with the device.
> > + */
> > + usleep_range(3, 5);
> > +
> > for (i = 0; i < devtype->nr_uart; ++i) {
> > s->p[i].line = i;
> > /* Initialize port data */
>
> Does this fix a problem? You don't have a Fixes tag nor did you describe
> a problem that arises if the is not there in the changelog.
Not for the moment, that is why I didn't put a Fixes tag.
A potential problem that can arise is that on a much faster processor, there is a chance that we could reach the first instruction that request a read/write before the reset post-delay.
Hugo.
