linux-kernel - [PATCH] firmware: ti_sci: Convert CPU latency constraint from us to ms

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Message-ID: <20250425153754.2141984-1-k-willis@ti.com>
Date: Fri, 25 Apr 2025 10:37:54 -0500
From: Kendall Willis <k-willis@...com>
To: <nm@...com>, <kristo@...nel.org>, <ssantosh@...nel.org>, <d-gole@...com>
CC: <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <k-willis@...com>
Subject: [PATCH] firmware: ti_sci: Convert CPU latency constraint from us to ms

Fix CPU resume latency constraint units sent to TI SCI firmware.
CPU latency constraints are set using the PM QoS framework. The PM QoS
framework uses usecs as the units for latency whereas the device manager
uses msecs, so a conversion is needed before passing to device manager.

Signed-off-by: Kendall Willis <k-willis@...com>
Reviewed-by: Dhruva Gole <d-gole@...com>
---
Test log [1] shows entry to MCU Only low power mode by sending a CPU
resume latency constraint of 100000 us using PM QoS. MCU Only is shown
to be entered by 0x1 as the printed mode.

[1] https://gist.github.com/kwillis01/059a2ca38232387b414bc6f4b87c7475
---
 drivers/firmware/ti_sci.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/ti_sci.c b/drivers/firmware/ti_sci.c
index 806a975fff22..bc138a837430 100644
--- a/drivers/firmware/ti_sci.c
+++ b/drivers/firmware/ti_sci.c
@@ -3670,6 +3670,7 @@ static int __maybe_unused ti_sci_suspend(struct device *dev)
 	struct ti_sci_info *info = dev_get_drvdata(dev);
 	struct device *cpu_dev, *cpu_dev_max = NULL;
 	s32 val, cpu_lat = 0;
+	u16 cpu_lat_ms;
 	int i, ret;
 
 	if (info->fw_caps & MSG_FLAG_CAPS_LPM_DM_MANAGED) {
@@ -3682,9 +3683,13 @@ static int __maybe_unused ti_sci_suspend(struct device *dev)
 			}
 		}
 		if (cpu_dev_max) {
-			dev_dbg(cpu_dev_max, "%s: sending max CPU latency=%u\n", __func__, cpu_lat);
+			/* PM QoS latency unit is usecs, TI SCI uses msecs */
+			cpu_lat_ms = cpu_lat / USEC_PER_MSEC;
+			dev_dbg(cpu_dev_max, "%s: sending max CPU latency=%u ms\n", __func__,
+				cpu_lat_ms);
 			ret = ti_sci_cmd_set_latency_constraint(&info->handle,
-								cpu_lat, TISCI_MSG_CONSTRAINT_SET);
+								cpu_lat_ms,
+								TISCI_MSG_CONSTRAINT_SET);
 			if (ret)
 				return ret;
 		}

base-commit: 393d0c54cae31317deaa9043320c5fd9454deabc
-- 
2.34.1