[PATCH v2 2/2] soc: qcom: pmic_glink: Handle GLINK intent allocation rejections

[Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxxxx>]

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:

    pmic_glink_altmode.pmic_glink_altmode pmic_glink.altmode.0: failed to send altmode request: 0x10 (-125)
    pmic_glink_altmode.pmic_glink_altmode pmic_glink.altmode.0: failed to request altmode notifications: -125
    ucsi_glink.pmic_glink_ucsi pmic_glink.ucsi.0: failed to send UCSI read request: -125
    qcom_battmgr.pmic_glink_power_supply pmic_glink.power-supply.0: failed to request power notifications

GLINK has been updated to distinguish between the cases where the remote
is going down (-ECANCELED) 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 5 second timeout is
used.

This patch was developed with input from Chris Lew.

Reported-by: Johan Hovold <johan@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/Zqet8iInnDhnxkT9@xxxxxxxxxxxxxxxxxxxx/#t
Cc: stable@xxxxxxxxxxxxxxx # rpmsg: glink: Handle rejected intent request better
Fixes: 58ef4ece1e41 ("soc: qcom: pmic_glink: Introduce base PMIC GLINK driver")
Tested-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
Reviewed-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxxxx>
---
 drivers/soc/qcom/pmic_glink.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/soc/qcom/pmic_glink.c b/drivers/soc/qcom/pmic_glink.c
index 9606222993fd78e80d776ea299cad024a0197e91..baa4ac6704a901661d1055c5caeaab61dc315795 100644
--- a/drivers/soc/qcom/pmic_glink.c
+++ b/drivers/soc/qcom/pmic_glink.c
@@ -4,6 +4,7 @@
  * Copyright (c) 2022, Linaro Ltd
  */
 #include <linux/auxiliary_bus.h>
+#include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
@@ -13,6 +14,8 @@
 #include <linux/soc/qcom/pmic_glink.h>
 #include <linux/spinlock.h>
 
+#define PMIC_GLINK_SEND_TIMEOUT (5 * HZ)
+
 enum {
 	PMIC_GLINK_CLIENT_BATT = 0,
 	PMIC_GLINK_CLIENT_ALTMODE,
@@ -112,13 +115,29 @@ 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;
+	bool timeout_reached = false;
+	unsigned long start;
 	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;
+		for (;;) {
+			ret = rpmsg_send(pg->ept, data, len);
+			if (ret != -EAGAIN)
+				break;
+
+			if (timeout_reached) {
+				ret = -ETIMEDOUT;
+				break;
+			}
+
+			usleep_range(1000, 5000);
+			timeout_reached = time_after(jiffies, start + PMIC_GLINK_SEND_TIMEOUT);
+		}
+	}
 	mutex_unlock(&pg->state_lock);
 
 	return ret;

-- 
2.43.0