Re: [PATCH V2 2/2] mailbox: introduce ARM SMC based mailbox

Hi Sudeep,

quoted

Subject: Re: [PATCH V2 2/2] mailbox: introduce ARM SMC based mailbox

On Mon, Jun 03, 2019 at 04:30:05PM +0800, peng.fan@nxp.com wrote:

quoted

From: Peng Fan <peng.fan@nxp.com>

This mailbox driver implements a mailbox which signals transmitted
data via an ARM smc (secure monitor call) instruction. The mailbox
receiver is implemented in firmware and can synchronously return data
when it returns execution to the non-secure world again.
An asynchronous receive path is not implemented.
This allows the usage of a mailbox to trigger firmware actions on SoCs
which either don't have a separate management processor or on which
such a core is not available. A user of this mailbox could be the SCP
interface.

Modified from Andre Przywara's v2 patch
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore
.kernel.org%2Fpatchwork%2Fpatch%2F812999%2F&amp;data=02%7C01%7

Cpeng.fa

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n%40nxp.com%7C6b37f78032e446be750e08d6f560e707%7C686ea1d3bc2b4
c6fa92cd

quoted

99c5c301635%7C0%7C0%7C636966193913988679&sdata=UNM4MTPs
brqoMqWStEy

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YzzwMEWTmX7hHO3TeNEz%2BOAw%3D&reserved=0

Cc: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
---

V2:
 Add interrupts notification support.

 drivers/mailbox/Kconfig                 |   7 ++
 drivers/mailbox/Makefile                |   2 +
 drivers/mailbox/arm-smc-mailbox.c       | 190

++++++++++++++++++++++++++++++++

quoted

 include/linux/mailbox/arm-smc-mailbox.h |  10 ++
 4 files changed, 209 insertions(+)
 create mode 100644 drivers/mailbox/arm-smc-mailbox.c  create mode
100644 include/linux/mailbox/arm-smc-mailbox.h

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig index

595542bfae85..c3bd0f1ddcd8 100644

--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig

@@ -15,6 +15,13 @@ config ARM_MHU
 	  The controller has 3 mailbox channels, the last of which can be
 	  used in Secure mode only.

+config ARM_SMC_MBOX
+	tristate "Generic ARM smc mailbox"
+	depends on OF && HAVE_ARM_SMCCC
+	help
+	  Generic mailbox driver which uses ARM smc calls to call into
+	  firmware for triggering mailboxes.
+
 config IMX_MBOX
 	tristate "i.MX Mailbox"
 	depends on ARCH_MXC || COMPILE_TEST

diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile index

c22fad6f696b..93918a84c91b 100644

--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile

@@ -7,6 +7,8 @@ obj-$(CONFIG_MAILBOX_TEST)	+= mailbox-test.o

 obj-$(CONFIG_ARM_MHU)	+= arm_mhu.o

+obj-$(CONFIG_ARM_SMC_MBOX)	+= arm-smc-mailbox.o
+
 obj-$(CONFIG_IMX_MBOX)	+= imx-mailbox.o

 obj-$(CONFIG_ARMADA_37XX_RWTM_MBOX)	+=

armada-37xx-rwtm-mailbox.o

quoted

diff --git a/drivers/mailbox/arm-smc-mailbox.c

b/drivers/mailbox/arm-smc-mailbox.c
new file mode 100644
index 000000000000..fef6e38d8b98

--- /dev/null
+++ b/drivers/mailbox/arm-smc-mailbox.c

@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2016,2017 ARM Ltd.
+ * Copyright 2019 NXP
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/mailbox_controller.h> #include
+<linux/mailbox/arm-smc-mailbox.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#define ARM_SMC_MBOX_USE_HVC	BIT(0)
+#define ARM_SMC_MBOX_USB_IRQ	BIT(1)
+
+struct arm_smc_chan_data {
+	u32 function_id;
+	u32 flags;
+	int irq;
+};
+
+static int arm_smc_send_data(struct mbox_chan *link, void *data) {
+	struct arm_smc_chan_data *chan_data = link->con_priv;
+	struct arm_smccc_mbox_cmd *cmd = data;
+	struct arm_smccc_res res;
+	u32 function_id;
+
+	if (chan_data->function_id != UINT_MAX)
+		function_id = chan_data->function_id;
+	else
+		function_id = cmd->a0;
+
+	if (chan_data->flags & ARM_SMC_MBOX_USE_HVC)
+		arm_smccc_hvc(function_id, cmd->a1, cmd->a2, cmd->a3,

cmd->a4,

quoted

+			      cmd->a5, cmd->a6, cmd->a7, &res);
+	else
+		arm_smccc_smc(function_id, cmd->a1, cmd->a2, cmd->a3,

cmd->a4,

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+			      cmd->a5, cmd->a6, cmd->a7, &res);
+

So how will the SMC/HVC handler in EL3/2 find which mailbox is being
referred with this command ? I prefer 2nd argument to be the mailbox
number.

You mean channel number as following?

@@ -37,10 +38,10 @@ static int arm_smc_send_data(struct mbox_chan *link, void *data)
                function_id = cmd->a0;

        if (chan_data->flags & ARM_SMC_MBOX_USE_HVC)
-               arm_smccc_hvc(function_id, cmd->a1, cmd->a2, cmd->a3, cmd->a4,
+               arm_smccc_hvc(function_id, chan_data->chan_id, cmd->a2, cmd->a3, cmd->a4,
                              cmd->a5, cmd->a6, cmd->a7, &res);
        else
-               arm_smccc_smc(function_id, cmd->a1, cmd->a2, cmd->a3, cmd->a4,
+               arm_smccc_smc(function_id, chan_data->chan_id, cmd->a2, cmd->a3, cmd->a4,
                              cmd->a5, cmd->a6, cmd->a7, &res);