On Mon, May 04, 2020 at 02:32:51PM +0530, Nagarjuna Kristam wrote:
> >On 28-04-2020 16:25, Thierry Reding wrote:
> > > On Wed, Apr 15, 2020 at 01:55:06PM +0530, Nagarjuna Kristam wrote:
[...]
> > > diff --git a/drivers/phy/tegra/xusb-tegra-cd.c b/drivers/phy/tegra/xusb-tegra-cd.c
> > > +static void tegra_xusb_padctl_utmi_pad_dcd(struct tegra_xusb_padctl *padctl,
> > > + u32 index)
> > > +{
> > > + u32 value;
> > > + int dcd_timeout_ms = 0;
> > > + bool ret = false;
> > > +
> > > + /* Turn on IDP_SRC */
> > > + value = padctl_readl(padctl, USB2_BATTERY_CHRG_OTGPADX_CTL0(index));
> > > + value |= OP_I_SRC_EN;
> > > + padctl_writel(padctl, value, USB2_BATTERY_CHRG_OTGPADX_CTL0(index));
> > > +
> > > + /* Turn on D- pull-down resistor */
> > > + value = padctl_readl(padctl, USB2_BATTERY_CHRG_OTGPADX_CTL1(index));
> > > + value |= USBON_RPD_OVRD_VAL;
> > > + padctl_writel(padctl, value, USB2_BATTERY_CHRG_OTGPADX_CTL1(index));
> > > +
> > > + /* Wait for TDCD_DBNC */
> > > + usleep_range(10000, 120000);
> > From the comment this looks like we're waiting for some hardware
> > condition. Can we somehow obtain this rather than implementing a fixed
> > sleep? Especially since the range here is so large.
> >
> As per data sheet we need to wait for 10 micro seconds as settle time.
Okay, so TDCD_DBNC is a value that comes from a timing diagram in a
datasheet? Seems fine to leave it as-is then. Perhaps add parentheses
and mention which exact datasheet that's from, and perhaps which figure
so that people can more easily reference it. Provided there is a
publicly available datasheet, of course.
Actually, one other thing: If the data sheet says to wait 10 us, why do
you use an upper range of 120 us? Shouldn't a range of 10-20 us be good
enough?
> > > + /* Wait for TVDPSRC_ON */
> > > + msleep(40);
> > Again, is this a hardware condition that we can wait on by polling a
> > register?
> >
> It HW settle time before reading registers.
Again, perhaps link to the datasheet, or alternatively describe in the
comment what this is waiting for. That is, something like:
/* wait for TVDPSRC_ON (wait for hardware to settle) */
or similar.
> > > + if (tegra_xusb_padctl_utmi_pad_secondary_charger_detect(padctl,
> > > + index))
> > > + chrg_type = CDP_TYPE;
> > > + else
> > > + chrg_type = DCP_TYPE;
> > > + } else {
> > > + chrg_type = SDP_TYPE;
> > > + }
> > > +
> > > + dev_dbg(&port->dev, "charger detected of type %d", chrg_type);
> > Do we have a string representation of this?
> >
> No String representation available. Shall i add one for wasy reading ?
Yeah, I think that'd be nice.
Thierry
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