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[46.91.229.123]) by smtp.gmail.com with ESMTPSA id d1sm18696767wrx.65.2020.05.04.08.50.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 May 2020 08:50:31 -0700 (PDT) Date: Mon, 4 May 2020 17:50:29 +0200 From: Thierry Reding To: Nagarjuna Kristam Cc: balbi@kernel.org, gregkh@linuxfoundation.org, jonathanh@nvidia.com, mark.rutland@arm.com, robh+dt@kernel.org, kishon@ti.com, devicetree@vger.kernel.org, linux-tegra@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V2 6/8] phy: tegra: xusb: Add support for charger detect Message-ID: <20200504155029.GB614153@ulmo> References: <1586939108-10075-1-git-send-email-nkristam@nvidia.com> <1586939108-10075-7-git-send-email-nkristam@nvidia.com> <20200428105510.GH3592148@ulmo> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="6sX45UoQRIJXqkqR" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.13.1 (2019-12-14) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org --6sX45UoQRIJXqkqR Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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/xu= sb-tegra-cd.c > > > +static void tegra_xusb_padctl_utmi_pad_dcd(struct tegra_xusb_padctl = *padctl, > > > + u32 index) > > > +{ > > > + u32 value; > > > + int dcd_timeout_ms =3D 0; > > > + bool ret =3D false; > > > + > > > + /* Turn on IDP_SRC */ > > > + value =3D padctl_readl(padctl, USB2_BATTERY_CHRG_OTGPADX_CTL0(index= )); > > > + value |=3D OP_I_SRC_EN; > > > + padctl_writel(padctl, value, USB2_BATTERY_CHRG_OTGPADX_CTL0(index)); > > > + > > > + /* Turn on D- pull-down resistor */ > > > + value =3D padctl_readl(padctl, USB2_BATTERY_CHRG_OTGPADX_CTL1(index= )); > > > + value |=3D 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. > >=20 > 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? > >=20 > 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 =3D CDP_TYPE; > > > + else > > > + chrg_type =3D DCP_TYPE; > > > + } else { > > > + chrg_type =3D SDP_TYPE; > > > + } > > > + > > > + dev_dbg(&port->dev, "charger detected of type %d", chrg_type); > > Do we have a string representation of this? > >=20 > No String representation available. Shall i add one for wasy reading ? Yeah, I think that'd be nice. 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