Re: [PATCH v11 4/4] firmware: ti_sci: add CPU latency constraint management

Nathan Chancellor
2024-09-03T00:54:24Z

Hi Markus,

On Thu, Aug 29, 2024 at 10:16:05PM +0200, Markus Schneider-Pargmann wrote:
> From: Kevin Hilman <khilman@baylibre.com>
>
> During system-wide suspend, check if any of the CPUs have PM QoS
> resume latency constraints set. If so, set TI SCI constraint.
>
> TI SCI has a single system-wide latency constraint, so use the max of
> any of the CPU latencies as the system-wide value.
>
> Note: DM firmware clears all constraints at resume time, so
> constraints need to be checked/updated/sent at each system suspend.
>
> Co-developed-by: Vibhore Vardhan <vibhore@ti.com>
> Signed-off-by: Vibhore Vardhan <vibhore@ti.com>
> Reviewed-by: Dhruva Gole <d-gole@ti.com>
> Signed-off-by: Dhruva Gole <d-gole@ti.com>
> Signed-off-by: Kevin Hilman <khilman@baylibre.com>
> Tested-by: Dhruva Gole <d-gole@ti.com>
> Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> ---
> drivers/firmware/ti_sci.c | 24 +++++++++++++++++++++++-
> 1 file changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/ti_sci.c b/drivers/firmware/ti_sci.c
> index 8482b7077eef..d5d64e5ffbd7 100644
> --- a/drivers/firmware/ti_sci.c
> +++ b/drivers/firmware/ti_sci.c
> @@ -10,6 +10,7 @@
> #define pr_fmt(fmt) "%s: " fmt, __func__
>
> #include <linux/bitmap.h>
> +#include <linux/cpu.h>
> #include <linux/debugfs.h>
> #include <linux/export.h>
> #include <linux/io.h>
> @@ -20,6 +21,7 @@
> #include <linux/of.h>
> #include <linux/of_platform.h>
> #include <linux/platform_device.h>
> +#include <linux/pm_qos.h>
> #include <linux/property.h>
> #include <linux/semaphore.h>
> #include <linux/slab.h>
> @@ -3669,7 +3671,27 @@ static int ti_sci_prepare_system_suspend(struct ti_sci_info *info)
> static int __maybe_unused ti_sci_suspend(struct device *dev)
> {
> struct ti_sci_info *info = dev_get_drvdata(dev);
> - int ret;
> + struct device *cpu_dev, *cpu_dev_max = NULL;
> + s32 val, cpu_lat = 0;
> + int i, ret;
> +
> + if (info->fw_caps & MSG_FLAG_CAPS_LPM_DM_MANAGED) {
> + for_each_possible_cpu(i) {
> + cpu_dev = get_cpu_device(i);
> + val = dev_pm_qos_read_value(cpu_dev, DEV_PM_QOS_RESUME_LATENCY);

This change is now in -next as commit 458d22d2e064 ("firmware: ti_sci:
add CPU latency constraint management"), where it breaks the build
when this driver is built as a module because dev_pm_qos_read_value() is
not exported to modules:

ERROR: modpost: "dev_pm_qos_read_value" [drivers/firmware/ti_sci.ko] undefined!

Obviously exporting it would fix the build but sometimes that is
controversial, hence just the report.

> + if (val != PM_QOS_RESUME_LATENCY_NO_CONSTRAINT) {
> + cpu_lat = max(cpu_lat, val);
> + cpu_dev_max = cpu_dev;
> + }
> + }
> + if (cpu_dev_max) {
> + dev_dbg(cpu_dev_max, "%s: sending max CPU latency=%u\n", __func__, cpu_lat);
> + ret = ti_sci_cmd_set_latency_constraint(&info->handle,
> + cpu_lat, TISCI_MSG_CONSTRAINT_SET);
> + if (ret)
> + return ret;
> + }
> + }
>
> ret = ti_sci_prepare_system_suspend(info);
> if (ret)
> --
> 2.45.2
>