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Message-ID: <HE1PR1001MB1002F9AD2691B631202CDE4780BC0@HE1PR1001MB1002.EURPRD10.PROD.OUTLOOK.COM>
Date: Mon, 17 Dec 2018 13:27:51 +0000
From: Adam Thomson <Adam.Thomson.Opensource@...semi.com>
To: Kyle Tso <kyletso@...gle.com>,
Adam Thomson <Adam.Thomson.Opensource@...semi.com>
CC: "linux@...ck-us.net" <linux@...ck-us.net>,
"heikki.krogerus@...ux.intel.com" <heikki.krogerus@...ux.intel.com>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"badhri@...gle.com" <badhri@...gle.com>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] usb: typec: tcpm: Extend the matching rules on PPS APDO
selection
On 17 December 2018 12:45, Kyle Tso wrote:
> On Mon, Dec 17, 2018 at 8:23 PM Adam Thomson
> <Adam.Thomson.Opensource@...semi.com> wrote:
> >
> > On 17 December 2018 02:48, Kyle Tso wrote:
> >
> > > Current matching rules ensure that the voltage range of selected
> > > Source Capability is entirely within the range defined in one of the
> > > Sink Capabilities. This is reasonable but not practical because Sink
> > > may not support wide range of voltage when sinking power while
> > > Source could advertise its capabilities in raletively wider range.
> > > For example, a Source PDO advertising 3.3V-11V@3A (9V
> >
> > relatively
> >
>
> noted!
> Thanks for the correction. I will fix this in the next patch.
>
> > > Prog of Fixed Nominal Voltage) will not be selected if the Sink
> > > requires 5V- 12V@3A PPS power. However, the Sink could work well if
> > > the requested voltage range in RDOs is 5V-11V@3A.
> > >
> > > Currently accepted:
> > > |--------- source -----|
> > > |----------- sink ---------------|
> > >
> > > Currently not accepted:
> > > |--------- source -----|
> > > |----------- sink ---------------|
> > >
> > > |--------- source -----|
> > > |----------- sink ---------------|
> > >
> > > |--------- source -----------------|
> > > |------ sink -------|
> > >
> > > To improve the usability, change the matching rules to what listed
> > > below:
> > > a. The Source PDO is selectable if any portion of the voltage range
> > > overlaps one of the Sink PDO's voltage range.
> > > b. The maximum operational voltage will be the lower one between the
> > > selected Source PDO and the matching Sink PDO.
> > > c. The maximum power will be the maximum operational voltage times the
> > > maximum current defined in the selected Source PDO d. Select the
> > > Source PDO with the highest maximum power
> > >
> > > Signed-off-by: Kyle Tso <kyletso@...gle.com>
> > >
> > > ---
> > > Changelog since v1:
> > > - updated the commit message as suggested by Guenter Roeck
> > > <linux@...ck- us.net>
> > > ---
> > > drivers/usb/typec/tcpm/tcpm.c | 29 +++++++++++++++++------------
> > > 1 file changed, 17 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/usb/typec/tcpm/tcpm.c
> > > b/drivers/usb/typec/tcpm/tcpm.c index 3620efee2688..3001df7bd602
> > > 100644
> > > --- a/drivers/usb/typec/tcpm/tcpm.c
> > > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > > @@ -2213,7 +2213,8 @@ static unsigned int
> > > tcpm_pd_select_pps_apdo(struct tcpm_port *port)
> > > unsigned int i, j, max_mw = 0, max_mv = 0;
> > > unsigned int min_src_mv, max_src_mv, src_ma, src_mw;
> > > unsigned int min_snk_mv, max_snk_mv;
> > > - u32 pdo;
> > > + unsigned int max_op_mv;
> > > + u32 pdo, src, snk;
> > > unsigned int src_pdo = 0, snk_pdo = 0;
> > >
> > > /*
> > > @@ -2263,16 +2264,18 @@ static unsigned int
> > > tcpm_pd_select_pps_apdo(struct tcpm_port *port)
> > > continue;
> > > }
> > >
> > > - if (max_src_mv <= max_snk_mv &&
> > > - min_src_mv >= min_snk_mv) {
> > > + if (min_src_mv <= max_snk_mv &&
> > > + max_src_mv >= min_snk_mv) {
> > > + max_op_mv = min(max_src_mv,
> > > max_snk_mv);
> > > + src_mw = (max_op_mv * src_ma)
> > > + / 1000;
> > > /* Prefer higher voltages if available */
> > > if ((src_mw == max_mw &&
> > > - min_src_mv > max_mv) ||
> > > + max_op_mv > max_mv) ||
> > > src_mw > max_mw) {
> >
> > Sorry I didn't raise this before, but came to mind this morning when I
> > was considering your updates again. What happens if the Source validly
> > provides two PPS APDOs, for example:
> >
> > 3.3V - 11V, 3A (9V programmable)
> > 3.3V - 16V, 3A (15V programmable)
> >
> > and the sink APDO is:
> >
> > 5V - 9V, 3A
> >
> > I think the code here will now select the higher range (15V
> > programmable) as it gives a larger power output value, even if the
> > sink can only support a voltage that's far smaller. I really don't
> > think this is correct. *If* you are going to allow selection of PPS
> > APDOs that provide a larger voltage range than the Sink can actually
> > cope with, then I think you should at least select the lower of those advertised
> which fulfils the needs of the Sink.
>
> Source:
> 3.3V - 11V, 3A (9V programmable)
> 3.3V - 16V, 3A (15V programmable)
>
> Sink
> 5V - 9V, 3A
>
> In this case, the Sink will select "3.3V - 11V, 3A (9V programmable)"
> because the
> "max_op_mv" when dealing with both Source Cap will be the same.
>
> See line#2269, "max_op_mv" will be limited by "max_snk_mv" which is 9V.
> And in line#2273, "max_op_mv" (of the second src_cap) fails the check because
> "max_mv", which is equal to the "max_op_mv" of the previous src_cap, is the
> same as it.
Ok, yes I missed the re-calculation of src_mw on line 2270. Apologies.
>
> 2267 if (min_src_mv <= max_snk_mv &&
> 2268 max_src_mv >= min_snk_mv) {
> 2269 max_op_mv = min(max_src_mv,
> max_snk_mv);
> 2270 src_mw = (max_op_mv * src_ma) / 1000;
> 2271 /* Prefer higher voltages if
> available */
> 2272 if ((src_mw == max_mw &&
> 2273 max_op_mv > max_mv) ||
> 2274 src_mw > max_mw) {
> 2275 src_pdo = i;
> 2276 snk_pdo = j;
> 2277 max_mw = src_mw;
> 2278 max_mv = max_op_mv;
> 2279 }
> 2280 }
>
> >
> > > src_pdo = i;
> > > snk_pdo = j;
> > > max_mw = src_mw;
> > > - max_mv = max_src_mv;
> > > + max_mv = max_op_mv;
> > > }
> > > }
> > > }
> > > @@ -2285,14 +2288,16 @@ static unsigned int
> > > tcpm_pd_select_pps_apdo(struct tcpm_port *port)
> > > }
> > >
> > > if (src_pdo) {
> > > - pdo = port->source_caps[src_pdo];
> > > -
> > > - port->pps_data.min_volt = pdo_pps_apdo_min_voltage(pdo);
> > > - port->pps_data.max_volt = pdo_pps_apdo_max_voltage(pdo);
> > > - port->pps_data.max_curr =
> > > - min_pps_apdo_current(pdo, port->snk_pdo[snk_pdo]);
> > > + src = port->source_caps[src_pdo];
> > > + snk = port->snk_pdo[snk_pdo];
> > > +
> > > + port->pps_data.min_volt =
> > > max(pdo_pps_apdo_min_voltage(src),
> > > + pdo_pps_apdo_min_voltage(snk));
> > > + port->pps_data.max_volt =
> > > min(pdo_pps_apdo_max_voltage(src),
> > > + pdo_pps_apdo_max_voltage(snk));
> > > + port->pps_data.max_curr = min_pps_apdo_current(src,
> > > + snk);
> > > port->pps_data.out_volt =
> > > - min(pdo_pps_apdo_max_voltage(pdo), port-
> > > >pps_data.out_volt);
> > > + min(port->pps_data.max_volt, port-
> > > >pps_data.out_volt);
> > > port->pps_data.op_curr =
> > > min(port->pps_data.max_curr, port->pps_data.op_curr);
> > > }
> > > --
> > > 2.20.0.405.gbc1bbc6f85-goog
> >
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