The initial implementation of request intent response handling dealt with two outcomes; granted allocations, and all other cases being considered -ECANCELLED (likely from "cancelling the operation as the remote is going down").

But on some channels intent allocation is not supported, instead the remote will pre-allocate and announce a fixed number of intents for the sender to use. If for such channels an rpmsg_send() is being invoked before any channels have been announced, an intent request will be issued and as this comes back rejected the call is failed with -ECANCELLED.

Given that this is reported in the same way as the remote being shut down, there's no way for the client to differentiate the two cases.

In line with the original GLINK design, change the return value to -EAGAIN for the case where the remote rejects an intent allocation request.

It's tempting to handle this case in the GLINK core, as we expect intents to show up in this case. But there's no way to distinguish between this case and a rejection for a too big allocation, nor is it possible to predict if a currently used (and seeminly suitable) intent will be returned for reuse or not. As such, returning the error to the client and allow it to react seems to be the only sensible solution.

In addition to this, commit 'c05dfce0b89e ("rpmsg: glink: Wait for intent, not just request ack")' changed the logic such that the code always wait for an intent request response and an intent. This works out in most cases, but in the event that a intent request is rejected and no further intent arrives (e.g. client asks for a too big intent), the code will stall for 10 seconds and then return -ETIMEDOUT; instead of a more suitable error.

This change also resulted in intent requests racing with the shutdown of the remote would be exposed to this same problem, unless some intent happens to arrive. A patch for this was developed and posted by Sarannya S [1], and has been incorporated here.

To summarize, the intent request can end in 4 ways: - Timeout, no response arrived => return -ETIMEDOUT - Abort TX, the edge is going away => return -ECANCELLED - Intent request was rejected => return -EAGAIN - Intent request was accepted, and an intent arrived => return 0

This patch was developed with input from Sarannya S, Deepak Kumar Singh, and Chris Lew.

[1] https://lore.kernel.org/all/20240925072328.1163183-1-quic_deesin@quicinc.com...

Fixes: c05dfce0b89e ("rpmsg: glink: Wait for intent, not just request ack") Cc: stable@vger.kernel.org Signed-off-by: Bjorn Andersson bjorn.andersson@oss.qualcomm.com --- drivers/rpmsg/qcom_glink_native.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c index 0b2f290069080638581a13b3a580054d31e176c2..d3af1dfa3c7d71b95dda911dfc7ad844679359d6 100644 --- a/drivers/rpmsg/qcom_glink_native.c +++ b/drivers/rpmsg/qcom_glink_native.c @@ -1440,14 +1440,18 @@ static int qcom_glink_request_intent(struct qcom_glink *glink, goto unlock;

ret = wait_event_timeout(channel->intent_req_wq, - READ_ONCE(channel->intent_req_result) >= 0 && - READ_ONCE(channel->intent_received), + READ_ONCE(channel->intent_req_result) == 0 || + (READ_ONCE(channel->intent_req_result) > 0 && + READ_ONCE(channel->intent_received)) || + glink->abort_tx, 10 * HZ); if (!ret) { dev_err(glink->dev, "intent request timed out\n"); ret = -ETIMEDOUT; + } else if (glink->abort_tx) { + ret = -ECANCELED; } else { - ret = READ_ONCE(channel->intent_req_result) ? 0 : -ECANCELED; + ret = READ_ONCE(channel->intent_req_result) ? 0 : -EAGAIN; }

unlock:

Some versions of the pmic_glink firmware does not allow dynamic GLINK intent allocations, attempting to send a message before the firmware has allocated its receive buffers and announced these intent allocations will fail. When this happens something like this showns up in the log:

[ 9.799719] pmic_glink_altmode.pmic_glink_altmode pmic_glink.altmode.0: failed to send altmode request: 0x10 (-125) [ 9.812446] pmic_glink_altmode.pmic_glink_altmode pmic_glink.altmode.0: failed to request altmode notifications: -125 [ 9.831796] ucsi_glink.pmic_glink_ucsi pmic_glink.ucsi.0: failed to send UCSI read request: -125

GLINK has been updated to distinguish between the cases where the remote is going down (-ECANCELLED) and the intent allocation being rejected (-EAGAIN).

Retry the send until intent buffers becomes available, or an actual error occur.

To avoid infinitely waiting for the firmware in the event that this misbehaves and no intents arrive, an arbitrary 10 second timeout is used.

This patch was developed with input from Chris Lew.

Reported-by: Johan Hovold johan@kernel.org Closes: https://lore.kernel.org/all/Zqet8iInnDhnxkT9@hovoldconsulting.com/#t Cc: stable@vger.kernel.org Signed-off-by: Bjorn Andersson bjorn.andersson@oss.qualcomm.com --- drivers/soc/qcom/pmic_glink.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/soc/qcom/pmic_glink.c b/drivers/soc/qcom/pmic_glink.c index 9606222993fd78e80d776ea299cad024a0197e91..221639f3da149da1f967dbc769a97d327ffd6c63 100644 --- a/drivers/soc/qcom/pmic_glink.c +++ b/drivers/soc/qcom/pmic_glink.c @@ -13,6 +13,8 @@ #include <linux/soc/qcom/pmic_glink.h> #include <linux/spinlock.h>

+#define PMIC_GLINK_SEND_TIMEOUT (10*HZ) + enum { PMIC_GLINK_CLIENT_BATT = 0, PMIC_GLINK_CLIENT_ALTMODE, @@ -112,13 +114,23 @@ EXPORT_SYMBOL_GPL(pmic_glink_client_register); int pmic_glink_send(struct pmic_glink_client *client, void *data, size_t len) { struct pmic_glink *pg = client->pg; + unsigned long start; + bool timeout_reached = false; int ret;

mutex_lock(&pg->state_lock); - if (!pg->ept) + if (!pg->ept) { ret = -ECONNRESET; - else - ret = rpmsg_send(pg->ept, data, len); + } else { + start = jiffies; + do { + timeout_reached = time_after(jiffies, start + PMIC_GLINK_SEND_TIMEOUT); + ret = rpmsg_send(pg->ept, data, len); + } while (ret == -EAGAIN && !timeout_reached); + + if (ret == -EAGAIN && timeout_reached) + ret = -ETIMEDOUT; + } mutex_unlock(&pg->state_lock);

return ret;