Re: [PATCH 2/6] firmware: ti_sci: Partial-IO support

Nishanth Menon
2024-05-24T05:47:26Z

On 10:02-20240523, Markus Schneider-Pargmann wrote:
> Add support for Partial-IO poweroff. In Partial-IO pins of a few modules
> can generate system wakeups while DDR memory is not powered resulting in
> a fresh boot of the system. The modules that can be wakeup sources are
> defined by the devicetree.
>
> Only wakeup sources that are actually enabled by the user will be
> considered as a an active wakeup source. If none of the wakeup sources
> are enabled the system will do a normal poweroff. If at least one wakeup
> source is enabled it will instead send a TI_SCI_MSG_PREPARE_SLEEP
> message from the sys_off handler. Sending this message will result in an
> immediate shutdown of the system. No execution is expected after this
> point. The code will enter an infinite loop.
>
> The wakeup source device nodes are gathered during probe. But they are
> only resolved to the actual devices in the sys_off handler, if they
> exist. If they do not exist, they are ignored.

Would have helped to provide link to relevant documentation here.

>
> Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> ---
> drivers/firmware/ti_sci.c | 135 +++++++++++++++++++++++++++++++++++++-
> drivers/firmware/ti_sci.h | 31 +++++++++
> 2 files changed, 165 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/ti_sci.c b/drivers/firmware/ti_sci.c
> index 160968301b1f..04730c4df2de 100644
> --- a/drivers/firmware/ti_sci.c
> +++ b/drivers/firmware/ti_sci.c
> @@ -116,6 +116,9 @@ struct ti_sci_info {
> u8 host_id;
> /* protected by ti_sci_list_mutex */
> int users;
> +
> + int nr_wakeup_sources;
> + struct device_node **wakeup_source_nodes;

Documentation please.
> };
>
> #define cl_to_ti_sci_info(c) container_of(c, struct ti_sci_info, cl)
> @@ -380,6 +383,28 @@ static void ti_sci_put_one_xfer(struct ti_sci_xfers_info *minfo,
> up(&minfo->sem_xfer_count);
> }
>
> +/**
> + * ti_sci_do_send() - Do one send, do not expect a response

is ti_sci_send_no_response() a better name?

I have a basic question about an API at kernel level that does'nt
return back.. but I will ask in the context of tisci_enter_partial_io
below.

> + * @info: Pointer to SCI entity information
> + * @xfer: Transfer to initiate
> + *
> + * Return: If send error, return corresponding error, else
> + * if all goes well, return 0.
> + */
> +static inline int ti_sci_do_send(struct ti_sci_info *info,
> + struct ti_sci_xfer *xfer)
> +{
> + int ret;

should'nt we make sure TI_SCI_FLAG_REQ_ACK_ON_PROCESSED is not set?
> +
> + ret = mbox_send_message(info->chan_tx, &xfer->tx_message);
> + if (ret < 0)
> + return ret;
> +
> + mbox_client_txdone(info->chan_tx, ret);
> +
> + return 0;
> +}
> +

I am not sure I like two functions sending mbox_send_message. what do
you think of the following?

Use xfer-> hdr.flags and check against TI_SCI_FLAG_REQ_ACK_ON_PROCESSED
itself to decide if ti_sci_do_xfer should expect a response or not?

> /**
> * ti_sci_do_xfer() - Do one transfer
> * @info: Pointer to SCI entity information
> @@ -3262,6 +3287,79 @@ static int tisci_reboot_handler(struct sys_off_data *data)
> return NOTIFY_BAD;
> }
>
> +/* Does not return if successful */

It wasn't clear from the commit message the strategy used. You are
triggering system off path here - do we loose the contents of
DDR in this flow? The power state needs to clearly described and the
rationale of using a variant of "off" path documented as well.

Looking further in to the code, I see we are unconditionally registering
the sys_off_handler based on ti,partial-io-wakeup-sources property being
present - how do we differentiate between actual PMIC power off desire
of user Vs just a few IO down power state for the user.

> +static int tisci_enter_partial_io(struct ti_sci_info *info)
> +{
> + struct ti_sci_msg_req_prepare_sleep *req;
> + struct ti_sci_xfer *xfer;
> + struct device *dev = info->dev;
> + int ret = 0;
> +
> + xfer = ti_sci_get_one_xfer(info, TI_SCI_MSG_PREPARE_SLEEP,
> + TI_SCI_FLAG_REQ_GENERIC_NORESPONSE,
> + sizeof(*req), sizeof(struct ti_sci_msg_hdr));
> + if (IS_ERR(xfer)) {
> + ret = PTR_ERR(xfer);
> + dev_err(dev, "Message alloc failed(%d)\n", ret);
> + return ret;
> + }
> +
> + req = (struct ti_sci_msg_req_prepare_sleep *)xfer->xfer_buf;
> + req->mode = TISCI_MSG_VALUE_SLEEP_MODE_PARTIAL_IO;
> + req->ctx_lo = 0;
> + req->ctx_hi = 0;
> + req->debug_flags = 0;
> +
> + ret = ti_sci_do_send(info, xfer);
> + if (ret) {
> + dev_err(dev, "Mbox send fail %d\n", ret);
> + goto fail;
> + }
> +
> +fail:
> + ti_sci_put_one_xfer(&info->minfo, xfer);
> +
> + return ret;
> +}
> +
> +static int tisci_sys_off_handler(struct sys_off_data *data)
> +{
> + struct ti_sci_info *info = data->cb_data;
> + int i;
> + int ret;
> + bool enter_partial_io = false;
> +
> + for (i = 0; i != info->nr_wakeup_sources; ++i) {
> + struct platform_device *pdev =
> + of_find_device_by_node(info->wakeup_source_nodes[i]);
> +
> + if (!pdev)
> + continue;
> +
> + if (device_may_wakeup(&pdev->dev)) {
> + dev_dbg(info->dev, "%pOFp identified as wakeup source\n",
> + info->wakeup_source_nodes[i]);
> + enter_partial_io = true;
> + }
> + }
> +
> + if (!enter_partial_io)
> + return NOTIFY_DONE;
> +
> + ret = tisci_enter_partial_io(info);
> +
> + if (ret)
> + dev_err(info->dev,
> + "Failed to enter Partial-IO %pe, halting system\n",
> + ERR_PTR(ret));

Is there no other diagnostics we can provide here?

> +
> + /* Halt system/code execution */
> + while (1)
> + ;
Why halt (1) -> spinning CPU in a while loop is not a power save mode
(at least idle?) :D

Why not fall through and loose power state context and allow the PMIC or
some other shutdown handler to attempt to power off?
> +
> + return NOTIFY_DONE;
> +}
> +
> /* Description for K2G */
> static const struct ti_sci_desc ti_sci_pmmc_k2g_desc = {
> .default_host_id = 2,
> @@ -3398,6 +3496,35 @@ static int ti_sci_probe(struct platform_device *pdev)
> goto out;
> }
>
> + if (of_property_read_bool(dev->of_node, "ti,partial-io-wakeup-sources")) {
> + info->nr_wakeup_sources =
> + of_count_phandle_with_args(dev->of_node,
> + "ti,partial-io-wakeup-sources",
> + NULL);
> + info->wakeup_source_nodes =
> + devm_kzalloc(dev, sizeof(*info->wakeup_source_nodes),
> + GFP_KERNEL);
> +
> + for (i = 0; i != info->nr_wakeup_sources; ++i) {
> + struct device_node *devnode =
> + of_parse_phandle(dev->of_node,
> + "ti,partial-io-wakeup-sources",
> + i);
> + info->wakeup_source_nodes[i] = devnode;
> + }
> +
> + ret = devm_register_sys_off_handler(dev,
> + SYS_OFF_MODE_POWER_OFF,
> + SYS_OFF_PRIO_FIRMWARE,
> + tisci_sys_off_handler,
> + info);
> + if (ret) {
> + dev_err(dev, "Failed to register sys_off_handler %pe\n",
> + ERR_PTR(ret));
> + goto out;
> + }
> + }
> +
> dev_info(dev, "ABI: %d.%d (firmware rev 0x%04x '%s')\n",
> info->handle.version.abi_major, info->handle.version.abi_minor,
> info->handle.version.firmware_revision,
> @@ -3407,7 +3534,13 @@ static int ti_sci_probe(struct platform_device *pdev)
> list_add_tail(&info->node, &ti_sci_list);
> mutex_unlock(&ti_sci_list_mutex);
>
> - return of_platform_populate(dev->of_node, NULL, NULL, dev);
> + ret = of_platform_populate(dev->of_node, NULL, NULL, dev);
> + if (ret) {
> + dev_err(dev, "platform_populate failed %pe\n", ERR_PTR(ret));
> + goto out;
> + }
> + return 0;

Unrelated change - please separate into different patch. Sounds like a
fix?

> +
> out:
> if (!IS_ERR(info->chan_tx))
> mbox_free_channel(info->chan_tx);
> diff --git a/drivers/firmware/ti_sci.h b/drivers/firmware/ti_sci.h
> index ef3a8214d002..6d8b12341f68 100644
> --- a/drivers/firmware/ti_sci.h
> +++ b/drivers/firmware/ti_sci.h
> @@ -35,6 +35,9 @@
> #define TI_SCI_MSG_QUERY_CLOCK_FREQ 0x010d
> #define TI_SCI_MSG_GET_CLOCK_FREQ 0x010e
>
> +/* Low Power Mode Requests */
> +#define TI_SCI_MSG_PREPARE_SLEEP 0x0300

Looking at https://software-dl.ti.com/tisci/esd/latest/2_tisci_msgs/pm/lpm.html#device-configuration-and-control-apis

Don't you need TISCI_MSG_SET_IO_ISOLATION support?

Also, reading https://software-dl.ti.com/tisci/esd/latest/2_tisci_msgs/pm/lpm.html#tisci-msg-enter-sleep

"This message is to be sent after TISCI_MSG_PREPARE_SLEEP and actually
triggers entry into the specified low power mode."

our call sequence seems to be just prepare_sleep and expect it to power
off the SoC? does'nt the PMIC need to be powered off?

> +
> /* Resource Management Requests */
> #define TI_SCI_MSG_GET_RESOURCE_RANGE 0x1500
>
> @@ -545,6 +548,34 @@ struct ti_sci_msg_resp_get_clock_freq {
> u64 freq_hz;
> } __packed;
>
> +#define TISCI_MSG_VALUE_SLEEP_MODE_DEEP_SLEEP 0x0
> +#define TISCI_MSG_VALUE_SLEEP_MODE_MCU_ONLY 0x1
> +#define TISCI_MSG_VALUE_SLEEP_MODE_STANDBY 0x2
> +#define TISCI_MSG_VALUE_SLEEP_MODE_PARTIAL_IO 0x3

Where are these values coming from?
https://software-dl.ti.com/tisci/esd/latest/2_tisci_msgs/pm/lpm.html#tisci-msg-prepare-sleep

Does not seem to have these?

I think we are picking from:
https://software-dl.ti.com/tisci/esd/latest/2_tisci_msgs/pm/lpm.html#supported-low-power-modes

? The documentation could use a little cleanup there :(

> +
> +/**
> + * struct tisci_msg_prepare_sleep_req - Request for TISCI_MSG_PREPARE_SLEEP.

s/tisci_msg_prepare_sleep_req/ti_sci_msg_req_prepare_sleep ?

> + *
> + * @hdr TISCI header to provide ACK/NAK flags to the host.
> + * @mode Low power mode to enter.
> + * @ctx_lo Low 32-bits of physical pointer to address to use for context save.
> + * @ctx_hi High 32-bits of physical pointer to address to use for context save.
> + * @debug_flags Flags that can be set to halt the sequence during suspend or
> + * resume to allow JTAG connection and debug.

There are no schemes to enable there? Are we going to manually modify
the driver for every step of the debug?

> + *
> + * This message is used as the first step of entering a low power mode. It
> + * allows configurable information, including which state to enter to be
> + * easily shared from the application, as this is a non-secure message and
> + * therefore can be sent by anyone.
> + */
> +struct ti_sci_msg_req_prepare_sleep {
> + struct ti_sci_msg_hdr hdr;
> + u8 mode;
> + u32 ctx_lo;
> + u32 ctx_hi;
> + u32 debug_flags;
> +} __packed;

Also are we supposed to use this header for other low power sequences?
From the definitions of TISCI_MSG_VALUE_SLEEP_MODE_* it looks like there
are additional usage? Just trying to understand if follow on patches
will not have to refactor things here.

> +
> #define TI_SCI_IRQ_SECONDARY_HOST_INVALID 0xff
>
> /**
> --
> 2.43.0
>

--
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3 1A34 DDB5 849D 1736 249D