Hi,
On 20-04-18 11:18, Jun Li wrote:
-----Original Message-----
From: Hans de Goede [mailto:hdego...@redhat.com]
Sent: 2018年4月18日 19:40
To: Jun Li <jun...@nxp.com>; li...@roeck-us.net;
heikki.kroge...@linux.intel.com
Cc: gre...@linuxfoundation.org; linux-usb@vger.kernel.org; dl-linux-imx
<linux-...@nxp.com>
Subject: Re: [PATCH RFC] usb: typec: tcpm: remove operating_snk_mw for rdo
Hi,
On 17-04-18 08:01, Li Jun wrote:
This patch is a further update for rdo based on [1], which removed
max_snk_ma/mv/mw but kept operating_snk_mw.
operating_snk_mw is only used to judge capability mismatch, per PD
spec, we can achieve this via compare the selected source PDO and
matching sink PDO, also after patch [1], we don't limit the PDO
matching between the same type, so the rdo operating and max
current/power calculation should be updated accordingly.
I do not believe that this is correct, lets take a device with a fusb302 tcpc
with
the following PDO-s:
PDO_FIXED(5000, 400, PDO_FIXED_FLAGS)
PDO_VAR(5000, 12000, 3000);
And an operating_snk_mw of 2500mW then according to your new code a
charger which supplies 12V 2A will now get the mismatch bit set even though it
is delivering 24W.
Per PD spec, my understanding is to judge capability mismatch, we should
use *max* current/power, not this operating power.
Ok, I'm not familiar with the PD spec, perhaps someone who knows it well
can comment here ?
In your case(VAR PDO), the max current is 3000mA, can I say the max
power is 3000mA * 5V = 15W? so the max current required at 12V
is 15W / 12V = 1.25A, so yes, the 12V@2A is enough, do you think
this kind of calculation is reasonable?
That does not sound unreasonable, the real question is when exactly should
we set the capability mismatch bit, once we have that more clear how to
implement this should become clear too.
Regards,
Hans
I really don't see any way to fix this and I believe we should just keep the
operating_snk_mw field.
I had the same worry of breaking existing users, but found there is something
not matching PD spec, so want to get comments, if we really need another input
(beside sink PDO) in practice, we can keep it.
Thanks
Jun
Regards
Hans
[1]https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2F
patchwork.kernel.org%2Fpatch%2F10342299%2F&data=02%7C01%7Cjun.li%4
0nxp
.com%7C796c943804cc4a333a7c08d5a5212e41%7C686ea1d3bc2b4c6fa92cd
99c5c30
1635%7C0%7C0%7C636596484284807487&sdata=BH74zzVppAi7Fa8jtRt2cwc
d%2F%2F
o6idNC5hk5zyoWIA4%3D&reserved=0
Signed-off-by: Li Jun <jun...@nxp.com>
---
drivers/usb/typec/tcpm.c | 52
++++++++++++++++++++++++++++++------------------
1 file changed, 33 insertions(+), 19 deletions(-)
diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c index
27192083..0be04b3 100644
--- a/drivers/usb/typec/tcpm.c
+++ b/drivers/usb/typec/tcpm.c
@@ -1854,28 +1854,42 @@ static int tcpm_pd_build_request(struct
tcpm_port *port, u32 *rdo)
else
mv = pdo_min_voltage(pdo);
- /* Select maximum available current within the sink pdo's limit */
- if (type == PDO_TYPE_BATT) {
- mw = min_power(pdo, matching_snk_pdo);
- ma = 1000 * mw / mv;
- } else {
- ma = min_current(pdo, matching_snk_pdo);
- mw = ma * mv / 1000;
- }
-
flags = RDO_USB_COMM | RDO_NO_SUSPEND;
- /* Set mismatch bit if offered power is less than operating power */
- max_ma = ma;
- max_mw = mw;
- if (mw < port->operating_snk_mw) {
- flags |= RDO_CAP_MISMATCH;
- if (type == PDO_TYPE_BATT &&
- (pdo_max_power(matching_snk_pdo) > pdo_max_power(pdo)))
- max_mw = pdo_max_power(matching_snk_pdo);
- else if (pdo_max_current(matching_snk_pdo) >
- pdo_max_current(pdo))
+ switch (type) {
+ case PDO_TYPE_FIXED:
+ case PDO_TYPE_VAR:
+ if (pdo_type(matching_snk_pdo) == PDO_TYPE_BATT)
+ max_ma = pdo_max_power(matching_snk_pdo) * 1000 / mv;
+ else
max_ma = pdo_max_current(matching_snk_pdo);
+
+ if (max_ma > pdo_max_current(pdo)) {
+ flags |= RDO_CAP_MISMATCH;
+ ma = pdo_max_current(pdo);
+ } else {
+ ma = max_ma;
+ }
+ break;
+ case PDO_TYPE_BATT:
+ if (pdo_type(matching_snk_pdo) == PDO_TYPE_BATT)
+ max_mw = pdo_max_power(matching_snk_pdo);
+ else
+ max_mw = pdo_max_current(matching_snk_pdo) *
+ pdo_min_voltage(matching_snk_pdo) /
+ 1000;
+
+ if (max_mw > pdo_max_power(pdo)) {
+ flags |= RDO_CAP_MISMATCH;
+ mw = pdo_max_power(pdo);
+ } else {
+ mw = max_mw;
+ }
+
+ ma = mw * 1000 / mv;
+ break;
+ default:
+ break;
}
tcpm_log(port, "cc=%d cc1=%d cc2=%d vbus=%d vconn=%s
polarity=%d",
--
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