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Message-ID: <3a8836dd-99d3-faff-af05-2032d609f594@arm.com>
Date: Wed, 22 Jan 2020 12:44:32 +0000
From: Cristian Marussi <cristian.marussi@....com>
To: Viresh Kumar <viresh.kumar@...aro.org>, arnd@...db.de,
Sudeep Holla <sudeep.holla@....com>
Cc: jassisinghbrar@...il.com, peng.fan@....com,
peter.hilber@...nsynergy.com, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V3] firmware: arm_scmi: Make scmi core independent of the
transport type
Hi
On 21/01/2020 08:27, Viresh Kumar wrote:
> The SCMI specification is fairly independent of the transport protocol,
> which can be a simple mailbox (already implemented) or anything else.
> The current Linux implementation however is very much dependent on the
> mailbox transport layer.
>
> This patch makes the SCMI core code (driver.c) independent of the
> mailbox transport layer and moves all mailbox related code to a new
> file: mailbox.c.
>
> We can now implement more transport protocols to transport SCMI
> messages.
>
> The transport protocols just need to provide struct scmi_transport_ops,
> with its version of the callbacks to enable exchange of SCMI messages.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
[snip]
> +/* Offset of fields within the above structure */
> +#define SHMEM_CHANNEL_STATUS offsetof(struct scmi_shared_mem, channel_status)
> +#define SHMEM_FLAGS offsetof(struct scmi_shared_mem, flags)
> +#define SHMEM_LENGTH offsetof(struct scmi_shared_mem, length)
> +#define SHMEM_MSG_HEADER offsetof(struct scmi_shared_mem, msg_header)
> +#define SHMEM_MSG_PAYLOAD offsetof(struct scmi_shared_mem, msg_payload)
> +
> +struct scmi_info;
> +
> +/**
> + * struct scmi_chan_info - Structure representing a SCMI channel information
> + *
> + * @payload: Transmit/Receive payload area
> + * @dev: Reference to device in the SCMI hierarchy corresponding to this
> + * channel
> + * @handle: Pointer to SCMI entity handle
> + * @transport_info: Transport layer related information
> + */
commment is obsolete
> +struct scmi_chan_info {
> + struct scmi_info *info;
> + struct device *dev;
> + struct scmi_handle *handle;
> + void *transport_info;
> +};
> +
> +/**
> + * struct scmi_transport_ops - Structure representing a SCMI transport ops
> + *
> + * @send_message: Callback to send a message
> + * @mark_txdone: Callback to mark tx as done
> + * @chan_setup: Callback to allocate and setup a channel
> + * @chan_free: Callback to free a channel
> + */
commment is obsolete but I would also ask: are all of these operations supposed to be mandatory supported
on any possible foreseeable transport ? (beside the obviously needed like send_message)
I'm asking because they are all called straight away from the driver core without any NULL check
so that if a new transport should not need one of them it will be forced to anyway implement a dummy one
to comply, which it will be needlessly invoked every time.
> +struct scmi_transport_ops {
> + bool (*chan_available)(struct device *dev, int idx);
> + int (*chan_setup)(struct scmi_chan_info *cinfo, struct device *dev, bool tx);
> + int (*chan_free)(int id, void *p, void *data);
> + int (*send_message)(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer);
> + void (*mark_txdone)(struct scmi_chan_info *cinfo, int ret);
> + u32 (*read32)(struct scmi_chan_info *cinfo, unsigned int offset);
> + void (*write32)(struct scmi_chan_info *cinfo, u32 val, unsigned int offset);
> + void (*memcpy_from)(struct scmi_chan_info *cinfo, void *to, unsigned int offset, long len);
> + void (*memcpy_to)(struct scmi_chan_info *cinfo, unsigned int offset, void *from, long len);
> +
> +};
> +
> +/**
> + * struct scmi_desc - Description of SoC integration
> + *
> + * @max_rx_timeout_ms: Timeout for communication with SoC (in Milliseconds)
> + * @max_msg: Maximum number of messages that can be pending
> + * simultaneously in the system
> + * @max_msg_size: Maximum size of data per message that can be handled.
> + */
comment is obsolete
> +struct scmi_desc {
> + struct scmi_transport_ops *ops;
> + int max_rx_timeout_ms;
> + int max_msg;
> + int max_msg_size;
> +};
> +
[big snip]
>
> -static const struct scmi_desc scmi_generic_desc = {
> - .max_rx_timeout_ms = 30, /* We may increase this if required */
> - .max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
> - .max_msg_size = 128,
> -};
> -
> /* Each compatible listed below must have descriptor associated with it */
> static const struct of_device_id scmi_of_match[] = {
> - { .compatible = "arm,scmi", .data = &scmi_generic_desc },
> + { .compatible = "arm,scmi", .data = &scmi_mailbox_desc },
> { /* Sentinel */ },
> };
minor thing: shouldn't the chosen transport being configurable at compile time with some
option like CONFIG_SCMI_TRANSPORT_MBOX ? or via DT ?
(minor thing in fact since as of now we have only one transport...)
>
> diff --git a/drivers/firmware/arm_scmi/mailbox.c b/drivers/firmware/arm_scmi/mailbox.c
> new file mode 100644
> index 000000000000..7509e7eb262a
> --- /dev/null
> +++ b/drivers/firmware/arm_scmi/mailbox.c
> @@ -0,0 +1,202 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * System Control and Management Interface (SCMI) Message Mailbox Transport
> + * driver.
> + *
> + * Copyright (C) 2019 ARM Ltd.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/device.h>
> +#include <linux/mailbox_client.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/slab.h>
> +
> +#include "common.h"
> +
> +/**
> + * struct scmi_mailbox - Structure representing a SCMI mailbox transport
> + *
> + * @cl: Mailbox Client
> + * @chan: Transmit/Receive mailbox channel
> + * @cinfo: SCMI channel info
> + */
comment is obsolete
> +struct scmi_mailbox {
> + struct mbox_client cl;
> + struct mbox_chan *chan;
> + struct scmi_chan_info *cinfo;
> + void __iomem *payload;
> +};
> +
[snip]
> +static void mailbox_memcpy_from(struct scmi_chan_info *cinfo, void *to,
> + unsigned int offset, long len)
> +{
> + struct scmi_mailbox *smbox = cinfo->transport_info;
> +
> + memcpy_fromio(to, smbox->payload + offset, len);
> +}
> +
> +static void mailbox_memcpy_to(struct scmi_chan_info *cinfo, unsigned int offset,
> + void *from, long len)
> +{
> + struct scmi_mailbox *smbox = cinfo->transport_info;
> +
> + memcpy_toio(smbox->payload + offset, from, len);
> +}
> +
> +static struct scmi_transport_ops scmi_mailbox_ops = {
> + .chan_available = mailbox_chan_available,
> + .chan_setup = mailbox_chan_setup,
> + .chan_free = mailbox_chan_free,
> + .send_message = mailbox_send_message,
> + .mark_txdone = mailbox_mark_txdone,
> + .read32 = mailbox_read32,
> + .write32 = mailbox_write32,
> + .memcpy_from = mailbox_memcpy_from,
> + .memcpy_to = mailbox_memcpy_to,
> +};
> +
> +const struct scmi_desc scmi_mailbox_desc = {
> + .ops = &scmi_mailbox_ops,
> + .max_rx_timeout_ms = 30, /* We may increase this if required */
> + .max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
> + .max_msg_size = 128,
> +};
>
Regards
Cristian
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