Messages in this thread Patch in this message | | | From | Cristian Marussi <> | Subject | [PATCH 2/7] firmware: arm_scmi: Add support for v3.2 NEGOTIATE_PROTOCOL_VERSION | Date | Wed, 14 Feb 2024 18:30:01 +0000 |
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Freshly introduced NEGOTIATE_PROTOCOL_VERSION allows the agent to ascertain upfront if a specific, usually older, protocol version is supported by the platform.
It is used by the agent in case the platform has advertised the support of a newer protocol version than the latest version supported by the agent, since backward compatibility cannot be automatically assumed.
Emit a warning about possible incompatibility when negotiation was not possible or just print the successfully negotiated protocol.
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> --- drivers/firmware/arm_scmi/driver.c | 65 ++++++++++++++++++++++++--- drivers/firmware/arm_scmi/protocols.h | 1 + 2 files changed, 61 insertions(+), 5 deletions(-)
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c index 4a64ad5c21ee..34d77802c990 100644 --- a/drivers/firmware/arm_scmi/driver.c +++ b/drivers/firmware/arm_scmi/driver.c @@ -86,6 +86,12 @@ struct scmi_xfers_info { * @users: A refcount to track effective users of this protocol. * @priv: Reference for optional protocol private data. * @version: Protocol version supported by the platform as detected at runtime. + * @negotiated_version: When the platform supports a newer protocol version, + * the agent will try to negotiate with the platform the + * usage of the newest version known to it, since + * backward compatibility is NOT automatically assured. + * This field is NON-zero when a successful negotiation + * has completed. * @ph: An embedded protocol handle that will be passed down to protocol * initialization code to identify this instance. * @@ -99,6 +105,7 @@ struct scmi_protocol_instance { refcount_t users; void *priv; unsigned int version; + unsigned int negotiated_version; struct scmi_protocol_handle ph; }; @@ -1815,6 +1822,44 @@ scmi_revision_area_get(const struct scmi_protocol_handle *ph) return pi->handle->version; } +/** + * scmi_protocol_version_negotiate - Negotiate protocol version + * + * @ph: A reference to the protocol handle. + * + * An helper to negotiate a protocol version different from the latest + * advertised as supported from the platform: on Success backward + * compatibility is assured by the platform. + * + * Return: 0 on Success + */ +static int scmi_protocol_version_negotiate(struct scmi_protocol_handle *ph) +{ + int ret; + struct scmi_xfer *t; + struct scmi_protocol_instance *pi = ph_to_pi(ph); + + /* At first check if NEGOTIATE_PROTOCOL_VERSION is supported ... */ + ret = scmi_protocol_msg_check(ph, NEGOTIATE_PROTOCOL_VERSION, NULL); + if (ret) + return ret; + + /* ... then attempt protocol version negotiation */ + ret = xfer_get_init(ph, NEGOTIATE_PROTOCOL_VERSION, + sizeof(__le32), 0, &t); + if (ret) + return ret; + + put_unaligned_le32(pi->proto->supported_version, t->tx.buf); + ret = do_xfer(ph, t); + if (!ret) + pi->negotiated_version = pi->proto->supported_version; + + xfer_put(ph, t); + + return ret; +} + /** * scmi_alloc_init_protocol_instance - Allocate and initialize a protocol * instance descriptor. @@ -1887,11 +1932,21 @@ scmi_alloc_init_protocol_instance(struct scmi_info *info, devres_close_group(handle->dev, pi->gid); dev_dbg(handle->dev, "Initialized protocol: 0x%X\n", pi->proto->id); - if (pi->version > proto->supported_version) - dev_warn(handle->dev, - "Detected UNSUPPORTED higher version 0x%X for protocol 0x%X." - "Backward compatibility is NOT assured.\n", - pi->version, pi->proto->id); + if (pi->version > proto->supported_version) { + ret = scmi_protocol_version_negotiate(&pi->ph); + if (!ret) { + dev_info(handle->dev, + "Protocol 0x%X successfully negotiated version 0x%X\n", + proto->id, pi->negotiated_version); + } else { + dev_warn(handle->dev, + "Detected UNSUPPORTED higher version 0x%X for protocol 0x%X.\n", + pi->version, pi->proto->id); + dev_warn(handle->dev, + "Trying version 0x%X. Backward compatibility is NOT assured.\n", + pi->proto->supported_version); + } + } return pi; diff --git a/drivers/firmware/arm_scmi/protocols.h b/drivers/firmware/arm_scmi/protocols.h index 26a3edd49fea..693019fff0f6 100644 --- a/drivers/firmware/arm_scmi/protocols.h +++ b/drivers/firmware/arm_scmi/protocols.h @@ -33,6 +33,7 @@ enum scmi_common_cmd { PROTOCOL_VERSION = 0x0, PROTOCOL_ATTRIBUTES = 0x1, PROTOCOL_MESSAGE_ATTRIBUTES = 0x2, + NEGOTIATE_PROTOCOL_VERSION = 0x10, }; /** -- 2.43.0
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