RE: [PATCH 2/2 v7] typec: tcpm: Only request matching pdos

From: Adam Thomson
Date: Thu Nov 23 2017 - 06:10:36 EST

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On 16 November 2017 01:02, Badhri Jagan Sridharan wrote:

> At present, TCPM code assumes that local device supports
> variable/batt pdos and always selects the pdo with highest
> possible power within the board limit. This assumption
> might not hold good for all devices. To overcome this,
> this patch makes TCPM only accept a source_pdo when there is
> a matching sink pdo.
>
> For Fixed pdos: The voltage should match between the
> incoming source_cap and the registered snk_pdo
> For Variable/Batt pdos: The incoming source_cap voltage
> range should fall within the registered snk_pdo's voltage
> range.
>
> Also, when the cap_mismatch bit is set, the max_power/current
> should be set to the max_current/power of the sink_pdo.
> This is according to:
>
> "If the Capability Mismatch bit is set to one
> The Maximum Operating Current/Power field may contain a value
> larger than the maximum current/power offered in the Source
> Capabilities messageâs PDO as referenced by the Object position field.
> This enables the Sink to indicate that it requires more current/power
> than is being offered. If the Sink requires a different voltage this
> will be indicated by its Sink Capabilities message.

Hi Badhri,

I have some queries on this change. At the moment the src/snk PDOs are hard
coded in the relevant PD controller driver (e.g. fusb302.c), and the only way
to update these is to call the tcpm_update_source_capabilities() or
tcpm_update_sink_capabilities() functions. However there are no real world
examples in the kernel where this happens. Where are these functions likely to
be called from, as wherever that is it will need a reference to the port?
Actually should we be adding DT bindings to set supported src/snk PDOs from FW,
if you're taking this approach to PDO selection?

This patch also seemingly leaves 'max_snk_mv', 'max_snk_ma' and 'max_snk_mv'
redundant, although those values can be configured from a PD controller driver
(e.g. fusb302 actually supports DT bindings which allow these to be set through
FW). Now these DT bindings are basically made redundant by your change as they
have no impact. Are we expecting these to be used again in the future, or should
these be removed? FYI, as part of my PPS patch set I have been using them as
part of the PPS APDO selection criteria, based on TCPM code prior to your
modifications, as for PPS we're interested in a wide range of voltages and
currents but want to stay within the platforms limits.

>
> Signed-off-by: Badhri Jagan Sridharan <Badhri@xxxxxxxxxx>
> Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
>
> ---
> Changelog since v1:
> - Rebased the patch on top of drivers/usb/type/tcpm.c
> - Added duplicate pdo check for variable/batt pdo.
> - Fixed tabs as suggested by dan.carpenter@xxxxxxxxxx
>
> Changelog since v2:
> - Rebase
>
> Changelog since v3:
> - Refactored code fixed formatting issues as suggested
> by heikki.krogerus@xxxxxxxxxxxxxxx
>
> Changelog since v4:
> - Rebase
>
> Changelog since v5:
> - handling the sink pdo index as pointer argument in tcpm_pd_select_pdo
> - ACK by heikki.krogerus@xxxxxxxxxxxxxxx
>
> Changelog since v6:
> - Added Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
>
> drivers/usb/typec/tcpm.c | 163 +++++++++++++++++++++++++++++++++++-----------
> -
> 1 file changed, 121 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
> index 8b637a4b474b..f4d563ee7690 100644
> --- a/drivers/usb/typec/tcpm.c
> +++ b/drivers/usb/typec/tcpm.c
> @@ -252,6 +252,9 @@ struct tcpm_port {
> unsigned int nr_src_pdo;
> u32 snk_pdo[PDO_MAX_OBJECTS];
> unsigned int nr_snk_pdo;
> + unsigned int nr_fixed; /* number of fixed sink PDOs */
> + unsigned int nr_var; /* number of variable sink PDOs */
> + unsigned int nr_batt; /* number of battery sink PDOs */
> u32 snk_vdo[VDO_MAX_OBJECTS];
> unsigned int nr_snk_vdo;
>
> @@ -1767,39 +1770,90 @@ static int tcpm_pd_check_request(struct tcpm_port
> *port)
> return 0;
> }
>
> -static int tcpm_pd_select_pdo(struct tcpm_port *port)
> +#define min_power(x, y) min(pdo_max_power(x), pdo_max_power(y))
> +#define min_current(x, y) min(pdo_max_current(x), pdo_max_current(y))
> +
> +static int tcpm_pd_select_pdo(struct tcpm_port *port, int *sink_pdo,
> + int *src_pdo)
> {
> - unsigned int i, max_mw = 0, max_mv = 0;
> + unsigned int i, j, max_mw = 0, max_mv = 0, mw = 0, mv = 0, ma = 0;
> int ret = -EINVAL;
>
> /*
> - * Select the source PDO providing the most power while staying within
> - * the board's voltage limits. Prefer PDO providing exp
> + * Select the source PDO providing the most power which has a
> + * matchig sink cap.
> */
> for (i = 0; i < port->nr_source_caps; i++) {
> u32 pdo = port->source_caps[i];
> enum pd_pdo_type type = pdo_type(pdo);
> - unsigned int mv, ma, mw;
>
> - if (type == PDO_TYPE_FIXED)
> - mv = pdo_fixed_voltage(pdo);
> - else
> - mv = pdo_min_voltage(pdo);
> -
> - if (type == PDO_TYPE_BATT) {
> - mw = pdo_max_power(pdo);
> - } else {
> - ma = min(pdo_max_current(pdo),
> - port->max_snk_ma);
> - mw = ma * mv / 1000;
> - }
> -
> - /* Perfer higher voltages if available */
> - if ((mw > max_mw || (mw == max_mw && mv > max_mv)) &&
> - mv <= port->max_snk_mv) {
> - ret = i;
> - max_mw = mw;
> - max_mv = mv;
> + if (type == PDO_TYPE_FIXED) {
> + for (j = 0; j < port->nr_fixed; j++) {
> + if (pdo_fixed_voltage(pdo) ==
> + pdo_fixed_voltage(port->snk_pdo[j])) {
> + ma = min_current(pdo, port->snk_pdo[j]);
> + mv = pdo_fixed_voltage(pdo);
> + mw = ma * mv / 1000;
> + if (mw > max_mw ||
> + (mw == max_mw && mv > max_mv)) {
> + ret = 0;
> + *src_pdo = i;
> + *sink_pdo = j;
> + max_mw = mw;
> + max_mv = mv;
> + }
> + /* There could only be one fixed pdo
> + * at a specific voltage level.
> + * So breaking here.
> + */
> + break;
> + }
> + }
> + } else if (type == PDO_TYPE_BATT) {
> + for (j = port->nr_fixed;
> + j < port->nr_fixed +
> + port->nr_batt;
> + j++) {
> + if (pdo_min_voltage(pdo) >=
> + pdo_min_voltage(port->snk_pdo[j]) &&
> + pdo_max_voltage(pdo) <=
> + pdo_max_voltage(port->snk_pdo[j])) {
> + mw = min_power(pdo, port->snk_pdo[j]);
> + mv = pdo_min_voltage(pdo);
> + if (mw > max_mw ||
> + (mw == max_mw && mv > max_mv)) {
> + ret = 0;
> + *src_pdo = i;
> + *sink_pdo = j;
> + max_mw = mw;
> + max_mv = mv;
> + }
> + }
> + }
> + } else if (type == PDO_TYPE_VAR) {
> + for (j = port->nr_fixed +
> + port->nr_batt;
> + j < port->nr_fixed +
> + port->nr_batt +
> + port->nr_var;
> + j++) {
> + if (pdo_min_voltage(pdo) >=
> + pdo_min_voltage(port->snk_pdo[j]) &&
> + pdo_max_voltage(pdo) <=
> + pdo_max_voltage(port->snk_pdo[j])) {
> + ma = min_current(pdo, port->snk_pdo[j]);
> + mv = pdo_min_voltage(pdo);
> + mw = ma * mv / 1000;
> + if (mw > max_mw ||
> + (mw == max_mw && mv > max_mv)) {
> + ret = 0;
> + *src_pdo = i;
> + *sink_pdo = j;
> + max_mw = mw;
> + max_mv = mv;
> + }
> + }
> + }
> }
> }
>
> @@ -1811,13 +1865,14 @@ static int tcpm_pd_build_request(struct tcpm_port
> *port, u32 *rdo)
> unsigned int mv, ma, mw, flags;
> unsigned int max_ma, max_mw;
> enum pd_pdo_type type;
> - int index;
> - u32 pdo;
> + int src_pdo_index, snk_pdo_index;
> + u32 pdo, matching_snk_pdo;
>
> - index = tcpm_pd_select_pdo(port);
> - if (index < 0)
> + if (tcpm_pd_select_pdo(port, &snk_pdo_index, &src_pdo_index) < 0)
> return -EINVAL;
> - pdo = port->source_caps[index];
> +
> + pdo = port->source_caps[src_pdo_index];
> + matching_snk_pdo = port->snk_pdo[snk_pdo_index];
> type = pdo_type(pdo);
>
> if (type == PDO_TYPE_FIXED)
> @@ -1825,26 +1880,28 @@ static int tcpm_pd_build_request(struct tcpm_port
> *port, u32 *rdo)
> else
> mv = pdo_min_voltage(pdo);
>
> - /* Select maximum available current within the board's power limit */
> + /* Select maximum available current within the sink pdo's limit */
> if (type == PDO_TYPE_BATT) {
> - mw = pdo_max_power(pdo);
> - ma = 1000 * min(mw, port->max_snk_mw) / mv;
> + mw = min_power(pdo, matching_snk_pdo);
> + ma = 1000 * mw / mv;
> } else {
> - ma = min(pdo_max_current(pdo),
> - 1000 * port->max_snk_mw / mv);
> + ma = min_current(pdo, matching_snk_pdo);
> + mw = ma * mv / 1000;
> }
> - ma = min(ma, port->max_snk_ma);
>
> flags = RDO_USB_COMM | RDO_NO_SUSPEND;
>
> /* Set mismatch bit if offered power is less than operating power */
> - mw = ma * mv / 1000;
> max_ma = ma;
> max_mw = mw;
> if (mw < port->operating_snk_mw) {
> flags |= RDO_CAP_MISMATCH;
> - max_mw = port->operating_snk_mw;
> - max_ma = max_mw * 1000 / mv;
> + 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))
> + max_ma = pdo_max_current(matching_snk_pdo);
> }
>
> tcpm_log(port, "cc=%d cc1=%d cc2=%d vbus=%d vconn=%s polarity=%d",
> @@ -1853,16 +1910,16 @@ static int tcpm_pd_build_request(struct tcpm_port
> *port, u32 *rdo)
> port->polarity);
>
> if (type == PDO_TYPE_BATT) {
> - *rdo = RDO_BATT(index + 1, mw, max_mw, flags);
> + *rdo = RDO_BATT(src_pdo_index + 1, mw, max_mw, flags);
>
> tcpm_log(port, "Requesting PDO %d: %u mV, %u mW%s",
> - index, mv, mw,
> + src_pdo_index, mv, mw,
> flags & RDO_CAP_MISMATCH ? " [mismatch]" : "");
> } else {
> - *rdo = RDO_FIXED(index + 1, ma, max_ma, flags);
> + *rdo = RDO_FIXED(src_pdo_index + 1, ma, max_ma, flags);
>
> tcpm_log(port, "Requesting PDO %d: %u mV, %u mA%s",
> - index, mv, ma,
> + src_pdo_index, mv, ma,
> flags & RDO_CAP_MISMATCH ? " [mismatch]" : "");
> }
>
> @@ -3593,6 +3650,19 @@ int tcpm_update_sink_capabilities(struct tcpm_port
> *port, const u32 *pdo,
> }
> EXPORT_SYMBOL_GPL(tcpm_update_sink_capabilities);
>
> +static int nr_type_pdos(const u32 *pdo, unsigned int nr_pdo,
> + enum pd_pdo_type type)
> +{
> + int count = 0;
> + int i;
> +
> + for (i = 0; i < nr_pdo; i++) {
> + if (pdo_type(pdo[i]) == type)
> + count++;
> + }
> + return count;
> +}
> +
> struct tcpm_port *tcpm_register_port(struct device *dev, struct tcpc_dev *tcpc)
> {
> struct tcpm_port *port;
> @@ -3638,6 +3708,15 @@ struct tcpm_port *tcpm_register_port(struct device
> *dev, struct tcpc_dev *tcpc)
> tcpc->config->nr_src_pdo);
> port->nr_snk_pdo = tcpm_copy_pdos(port->snk_pdo, tcpc->config-
> >snk_pdo,
> tcpc->config->nr_snk_pdo);
> + port->nr_fixed = nr_type_pdos(port->snk_pdo,
> + port->nr_snk_pdo,
> + PDO_TYPE_FIXED);
> + port->nr_var = nr_type_pdos(port->snk_pdo,
> + port->nr_snk_pdo,
> + PDO_TYPE_VAR);
> + port->nr_batt = nr_type_pdos(port->snk_pdo,
> + port->nr_snk_pdo,
> + PDO_TYPE_BATT);
> port->nr_snk_vdo = tcpm_copy_vdos(port->snk_vdo, tcpc->config-
> >snk_vdo,
> tcpc->config->nr_snk_vdo);
>
> --
> 2.15.0.448.gf294e3d99a-goog
>
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