[PATCH 0/3] mailbox: New mailbox driver for ST

[PATCH 0/3] mailbox: New mailbox driver for ST

[Lee Jones]

This set provides support for ST's Mailbox IP.

In order to save IRQ lines, current platforms have been only been
given a single interrupt for receiving messages from co-processors.
The best way to work around this limitation is to use Mailbox 1
(A9) as the receiving MB.  This driver/binding then has the ability
to map the remaining Mailboxes back to Mailbox 1 where threaded
interrupts are used to extract data to send back to the user.

Lee Jones (3):
  ARM: STi: stih407-family: Add nodes for Mailbox
  mailbox: dt: Supply bindings for ST's Mailbox IP
  mailbox: Add support for ST's Mailbox IP

 .../devicetree/bindings/mailbox/sti-mailbox.txt    |  66 ++
 arch/arm/boot/dts/stih407-family.dtsi              |  67 +++
 drivers/mailbox/Kconfig                            |   7 +
 drivers/mailbox/Makefile                           |   2 +
 drivers/mailbox/mailbox-sti.c                      | 664 +++++++++++++++++++++
 include/linux/mailbox_sti.h                        | 128 ++++
 6 files changed, 934 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/sti-mailbox.txt
 create mode 100644 drivers/mailbox/mailbox-sti.c
 create mode 100644 include/linux/mailbox_sti.h

-- 
1.9.1

[PATCH 1/3] ARM: STi: stih407-family: Add nodes for Mailbox

[Lee Jones]

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 arch/arm/boot/dts/stih407-family.dtsi | 67 +++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/arch/arm/boot/dts/stih407-family.dtsi b/arch/arm/boot/dts/stih407-family.dtsi
index 0eb39d9..23916ac 100644
--- a/arch/arm/boot/dts/stih407-family.dtsi
+++ b/arch/arm/boot/dts/stih407-family.dtsi
@@ -12,6 +12,13 @@
 	#address-cells = <1>;
 	#size-cells = <1>;
 
+	aliases {
+		mailbox0 = &mailbox0;
+		mailbox1 = &mailbox1;
+		mailbox2 = &mailbox2;
+		mailbox3 = &mailbox3;
+	};
+
 	cpus {
 		#address-cells = <1>;
 		#size-cells = <0>;
@@ -275,6 +282,66 @@
 			status = "disabled";
 		};
 
+		mailbox0: mailbox at 0  {
+			compatible = "st,stih407-mailbox";
+			#address-cells = <1>;
+			#size-cells = <1>;
+			#mbox-cells = <1>;
+			reg = <0x8f00000 0x1000>;
+			reg-names = "mbox-reg";
+			interrupts = <GIC_SPI 1 IRQ_TYPE_NONE>;
+			interrupt-names = "mb0_irq";
+			status = "okay";
+			st,name = "a9";
+			st,mbox-rx;
+			st,mbox-rx-id = <0>;
+			st,mbox-names = "chan0_a9";
+			st,mbox-chans = <0 0 0 0>;
+		};
+
+		mailbox1: mailbox at 1 {
+			compatible = "st,stih407-mailbox";
+			#address-cells = <1>;
+			#size-cells = <1>;
+			#mbox-cells = <1>;
+			reg = <0x8f01000 0x1000>;
+			reg-names = "mbox-reg";
+			status = "okay";
+			st,name = "st231_gp_1";
+			st,mbox-rx-id = <0>;
+			st,mbox-names = "chan0_gp1";
+			st,mbox-chans = <0 1 0 1>;
+		};
+
+		mailbox2: mailbox at 2 {
+			compatible = "st,stih407-mailbox";
+			#address-cells = <1>;
+			#size-cells = <1>;
+			#mbox-cells = <1>;
+			reg = <0x8f02000 0x1000>;
+			reg-names = "mbox-reg";
+			status = "okay";
+			st,name = "st231_gp_0";
+			st,mbox-rx-id = <0>;
+			st,mbox-names = "chan0_gp0";
+			st,mbox-chans = <4 0 4 0>;
+		};
+
+		mailbox3: mailbox at 3 {
+			compatible = "st,stih407-mailbox";
+			#address-cells = <1>;
+			#size-cells = <1>;
+			#mbox-cells = <1>;
+			reg = <0x8f03000 0x1000>;
+			reg-names = "mbox-reg";
+			status = "okay";
+			st,name = "st231_audio_video";
+			st,mbox-rx-id = <0>;
+			st,mbox-names = "chan0_video", "chan0_audio";
+			st,mbox-chans = <0 3 0 3>,
+					<16 3 16 3>;
+		};
+
 		st231_gp0: st231-gp0 at 0 {
 			compatible = "st,st231-rproc";
 			reg = <0x40000000 0x01000000>;
-- 
1.9.1

[PATCH 2/3] mailbox: dt: Supply bindings for ST's Mailbox IP

[Lee Jones]

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 .../devicetree/bindings/mailbox/sti-mailbox.txt    | 66 ++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/sti-mailbox.txt

diff --git a/Documentation/devicetree/bindings/mailbox/sti-mailbox.txt b/Documentation/devicetree/bindings/mailbox/sti-mailbox.txt
new file mode 100644
index 0000000..c965c13
--- /dev/null
+++ b/Documentation/devicetree/bindings/mailbox/sti-mailbox.txt
@@ -0,0 +1,66 @@
+ST Microelectronics Mailbox Driver
+
+Required properties:
+- compatible		: Should be "st,stih407-mailbox"
+- reg			: Offset and length of the register set for the device
+- reg-names		: Should contain the reg name "mbox-reg".
+- st,name		: Name of the mailbox
+- st,mbox-chans		: Mbox/channels descriptor data private to each channel.
+			  The 4 cells represent the following data:
+				Cell #1 (rx_id) - rx mbox num in an instance.
+				Cell #2 (rx_inst) - rx mbox instance num.
+				Cell #3 (tx_id) - tx mbox num in an instance.
+				Cell #4 (tx_inst) - tx mbox instance num.
+
+			  Note that an IP Mailbox is composed by 4 instances and
+			  each instance is composed by 32 mailboxes.
+			  You define here the configuration of a channel (at
+			  framework level).
+
+Optional properties
+- st,mbox-rx		: Indicaties if the mailbox can be used as Rx mailbox.
+- st,mbox-rx-id		: If a Rx mailbox is affected to a Tx mailbox (to have
+			  full-duplex channel), this field indiactes the Id of
+			  the Rx mailbox to use.
+- interrupts		: Contains the IRQ line for a RX mailbox.
+- interrupt-names	: Should contain the interrupt name.
+
+Examples:
+
+mailbox0: mailbox at 0 {
+	compatible = "st,stih407-mailbox";
+	#address-cells = <1>;
+	#size-cells = <1>;
+	#mbox-cells = <1>;
+	reg = <0x8f00000 0x1000>;
+	reg-names = "mbox-reg";
+	interrupts = <GIC_SPI 1 IRQ_TYPE_NONE>;
+	interrupt-names = "mb0_irq";
+	st,name = "a9";
+	st,mbox-rx;
+	st,mbox-rx-id = <0>;
+	st,mbox-chans = <0 1 0 1>;
+};
+
+mailbox3: mailbox at 3 {
+	compatible = "st,stih407-mailbox";
+	#address-cells = <1>;
+	#size-cells = <1>;
+	#mbox-cells = <1>;
+	reg = <0x8f03000 0x100>;
+	reg-names = "mbox-reg";
+	st,name = "st231_video";
+	st,mbox-rx-id = <0>;
+	st,mbox-chans = <2 1 2 1>;
+};
+
+In this configuration, if you use channel 0 you will have the following
+configuration:
+- "chan0_video" will use mailbox0 as Rx mailbox.
+- "chan0_video" will use instance 1, bit 2 in mailbox0 for rx.
+- "chan0_video" will use instance 1, bit 2 in mailbox3 for tx.
+
+If you declare a channel only for Rx, you have to set magic number 0xff
+for tx_id and tx_instance.
+If you declare a channel only for Tx, you have to set magic number 0xff
+for rx_id and rx_instance.
-- 
1.9.1

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Lee Jones]

ST's platforms currently support a maximum of 5 channels, one for
each of the co-processors situated on the platforms.  The
difficulty with this IP is the fact that there is only one RX IRQ,
which requires some special handling within the driver.  In this
implementation channel 1, which is always the A9 channel, is
divided and allocated to each of the remaining Mailbox channels in
order for them to use it as their RX channel.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 drivers/mailbox/Kconfig       |   7 +
 drivers/mailbox/Makefile      |   2 +
 drivers/mailbox/mailbox-sti.c | 664 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/mailbox_sti.h   | 128 ++++++++
 4 files changed, 801 insertions(+)
 create mode 100644 drivers/mailbox/mailbox-sti.c
 create mode 100644 include/linux/mailbox_sti.h

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index c04fed9..b524806 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -45,4 +45,11 @@ config PCC
 	  states). Select this driver if your platform implements the
 	  PCC clients mentioned above.
 
+config STI_MBOX
+	tristate "STI Mailbox framework support"
+	depends on ARCH_STI && OF
+	help
+	  Mailbox implementation for STMicroelectonics family chips with
+	  hardware for interprocessor communication.
+
 endif
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index dd412c2..d0b2f05 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -7,3 +7,5 @@ obj-$(CONFIG_PL320_MBOX)	+= pl320-ipc.o
 obj-$(CONFIG_OMAP2PLUS_MBOX)	+= omap-mailbox.o
 
 obj-$(CONFIG_PCC)		+= pcc.o
+
+obj-$(CONFIG_STI_MBOX)		+= mailbox-sti.o
diff --git a/drivers/mailbox/mailbox-sti.c b/drivers/mailbox/mailbox-sti.c
new file mode 100644
index 0000000..c5e52fc
--- /dev/null
+++ b/drivers/mailbox/mailbox-sti.c
@@ -0,0 +1,664 @@
+/*
+ * STi Mailbox
+ *
+ * Copyright (C) 2015 ST Microelectronics
+ *
+ * Author: Alexandre Torgue <alexandre.torgue@st.com> for ST Microelectronics
+ * Author: Olivier Lebreton <olivier.lebreton@st.com> for ST Microelectronics
+ * Author: Loic Pallardy <loic.pallardy@st.com> for ST Microelectronics
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/bitops.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
+#include <linux/mailbox_controller.h>
+#include <linux/mailbox_sti.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#define REG_MBOX_INT_STA_VAL	0x04
+#define REG_MBOX_INT_STA_SET	0x24
+#define REG_MBOX_INT_STA_CLR	0x44
+#define REG_MBOX_ENA_VAL	0x64
+#define REG_MBOX_ENA_SET	0x84
+#define REG_MBOX_ENA_CLR	0xa4
+
+#define ALL_MBOX_BITS(_nb)	(BIT(_nb) - 1)
+
+/*
+ * A Mailbox can be used in several configurations:
+ *	- Only for TX dir (no IRQ)
+ *	- Only for RX dir (one IRQ on A9)
+ *	- Both
+ * Max number of mailbox on our SoC (currently 5)
+ * mdev_rx represents potential Rx mailbox which could be used by a channel
+ */
+#define MBOX_HW_MAX		5
+#define MBOX_NO_RX		0xff
+
+static struct sti_mbox_device mdev_rxs[MBOX_HW_MAX];
+
+static DEFINE_SPINLOCK(sti_mbox_irqs_lock);
+
+/* Mailbox H/W preparations */
+static struct irq_chip sti_mbox_irq_chip;
+
+static inline bool sti_mbox_chan_is_rx(struct sti_mbox_dev_data *mbox)
+{
+	return ((mbox->rx_id != MBOX_NO_RX) && (mbox->rx_inst != MBOX_NO_RX));
+}
+
+static inline bool sti_mbox_chan_is_tx(struct sti_mbox_dev_data *mbox)
+{
+	return ((mbox->tx_id != MBOX_NO_RX) && (mbox->tx_inst != MBOX_NO_RX));
+}
+
+/* Message management */
+static void sti_mbox_read(struct sti_mbox_dev_data *mbox,
+			  struct sti_mbox_msg *msg)
+{
+	struct sti_mbox_data *md = &mbox->mdata;
+	void __iomem *hdr = md->rx_addr;
+
+	/* Read data payload */
+	msg->dsize = readb(hdr);
+	msg->pdata = (u8*)++hdr;
+}
+
+static void sti_mbox_write(struct sti_mbox_dev_data *mbox, void *data)
+{
+	struct sti_mbox_data *md = &mbox->mdata;
+	struct sti_mbox_msg *msg = (struct sti_mbox_msg *)data;
+	u32 len = msg->dsize;
+	void __iomem *hdr;
+	u8 *wrb;
+	unsigned int j;
+
+	hdr = md->tx_addr;
+
+	/* Payload size */
+	writeb((u8)len, hdr);
+
+	wrb = msg->pdata;
+	if (!wrb)
+		return;
+
+	/* Payload data */
+	for (j = 0, hdr++; j < len; j++, wrb++, hdr++)
+		writeb(*wrb, hdr);
+}
+
+/* Mailbox IRQ handle functions */
+static void sti_mbox_enable_irq(struct sti_mbox_instance *mbinst, u32 msk)
+{
+	struct sti_mbox_device *mdev = mbinst->parent;
+	struct sti_mbox_attribute *p = mdev->cfg;
+	void __iomem *base;
+	unsigned long flags;
+
+	base = mdev->mdev_rx->mbox_reg_base + (mbinst->id * p->num_inst);
+	spin_lock_irqsave(&sti_mbox_irqs_lock, flags);
+	mbinst->irq_msk |= msk;
+
+	writel_relaxed(msk, base + p->reg_ena_set);
+
+	spin_unlock_irqrestore(&sti_mbox_irqs_lock, flags);
+}
+
+static void sti_mbox_disable_irq(struct sti_mbox_instance *mbinst, u32 msk)
+{
+	struct sti_mbox_device *mdev = mbinst->parent;
+	struct sti_mbox_attribute *p = mdev->cfg;
+	void __iomem *base;
+	unsigned long flags;
+
+	base = mdev->mdev_rx->mbox_reg_base + (mbinst->id * p->num_inst);
+	spin_lock_irqsave(&sti_mbox_irqs_lock, flags);
+	mbinst->irq_msk &= ~msk;
+	writel_relaxed(msk, base + p->reg_ena_clr);
+	spin_unlock_irqrestore(&sti_mbox_irqs_lock, flags);
+}
+
+static void sti_mbox_clr_irq(struct sti_mbox_instance *mbinst, u32 msk)
+{
+	struct sti_mbox_device *mdev = mbinst->parent;
+	struct sti_mbox_attribute *p = mdev->cfg;
+	void __iomem *base;
+
+	base = mdev->mdev_rx->mbox_reg_base + (mbinst->id * p->num_inst);
+	writel_relaxed(msk, base + p->reg_clr);
+}
+
+static irqreturn_t sti_mbox_thread_interrupt(int irq, void *data)
+{
+	struct mbox_chan *chan = data;
+	struct sti_mbox_dev_data *mbox = chan->con_priv;
+	struct sti_mbox_device *mdev_rx = mbox->parent->mdev_rx;
+
+	mbox_chan_received_data(chan, (void *)mbox->msg);
+	sti_mbox_enable_irq(mdev_rx->mbinst[mbox->rx_inst], BIT(mbox->rx_id));
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t sti_mbox_interrupt(int irq, void *data)
+{
+	struct mbox_chan *chan = data;
+	struct sti_mbox_dev_data *mbox = chan->con_priv;
+	struct sti_mbox_data *md = &mbox->mdata;
+	struct sti_mbox_device *mdev_rx = mbox->parent->mdev_rx;
+
+	sti_mbox_disable_irq(mdev_rx->mbinst[mbox->rx_inst], BIT(mbox->rx_id));
+
+	if (md->rx_addr != NULL)
+		sti_mbox_read(mbox, mbox->msg);
+
+	return IRQ_WAKE_THREAD;
+}
+
+
+static irqreturn_t sti_mbox_irq_handler(int irq, void *data)
+{
+	struct sti_mbox_device *mdev_rx = data;
+	struct sti_mbox_attribute *p = mdev_rx->cfg;
+	struct irq_domain *mbox_irq_domain;
+	void __iomem *base;
+	u32 irq_chan;
+	unsigned long bits = 0;
+	u8 n;
+	int i;
+
+	base = mdev_rx->mbox_reg_base + mdev_rx->cfg->reg_val;
+
+	for (i = 0; i < p->num_inst; i++) {
+		bits = readl_relaxed(base + (i * p->num_inst));
+		if (bits)
+			break;
+	}
+
+	if (unlikely(!bits))
+		return IRQ_NONE;
+
+	mbox_irq_domain = mdev_rx->mbinst[i]->irq_domain;
+
+	for (n = 0; bits; n++) {
+		if (test_and_clear_bit(n, &bits)) {
+
+			irq_chan = irq_find_mapping(mbox_irq_domain, n);
+			if (mdev_rx->mbinst[i]->irq_msk & BIT(n)) {
+				generic_handle_irq(irq_chan);
+				sti_mbox_clr_irq(mdev_rx->mbinst[i], BIT(n));
+
+			} else
+				dev_warn(mdev_rx->dev,
+					 "Unexpected mailbox interrupt\n"
+					 "mask: %x\n",
+					 mdev_rx->mbinst[i]->irq_msk);
+		}
+	}
+	return IRQ_HANDLED;
+}
+
+/* Channel management */
+static int sti_mbox_startup(struct mbox_chan *chan)
+{
+	struct sti_mbox_dev_data *mbox = chan->con_priv;
+	struct sti_mbox_device *mdev = mbox->parent;
+	char name[32];
+	int ret = 0;
+
+	/* Allocate Rx msg per channel */
+	mbox->msg = devm_kzalloc(mdev->dev, sizeof(struct sti_mbox_device),
+				  GFP_KERNEL);
+	if (!mbox->msg)
+		return -ENOMEM;
+
+	if (sti_mbox_chan_is_rx(mbox)) {
+		snprintf(name, sizeof(name), "%s-%d", mdev->name,
+			 mbox->chan_id);
+		/* IRQ automatically enabled */
+		ret = request_threaded_irq(mbox->irq, sti_mbox_interrupt,
+					   sti_mbox_thread_interrupt,
+					   IRQF_SHARED, name, chan);
+		if (ret)
+			dev_err(mdev->dev,
+				"failed to register mailbox interrupt:%d\n",
+				ret);
+	}
+
+	return ret;
+}
+
+static void sti_mbox_shutdown(struct mbox_chan *chan)
+{
+	struct sti_mbox_dev_data *mbox = chan->con_priv;
+	struct sti_mbox_device *mdev = mbox->parent;
+
+	/* IRQ automatically disabled */
+	free_irq(mbox->irq, chan);
+
+	/* Free Rx msg */
+	devm_kfree(mdev->dev, mbox->msg);
+}
+
+static bool sti_mbox_tx_is_ready(struct mbox_chan *chan)
+{
+	struct sti_mbox_dev_data *mbox = chan->con_priv;
+	struct sti_mbox_device *mdev = mbox->parent;
+	struct sti_mbox_attribute *p = mdev->cfg;
+	void __iomem *base;
+
+	/*
+	 *  Check if tx mbox has got a pending interrupt, and if it is enabled
+	 *  before sending a new message
+	 */
+	base = mdev->mbox_reg_base + (p->num_inst * mbox->tx_inst);
+
+	if (!(readl_relaxed(base + p->reg_ena_val) & BIT(mbox->tx_id))) {
+		dev_warn(mdev->dev, "Mbox: %d, inst: %x, chan: %x disabled\n",
+			mdev->id, mbox->tx_inst, mbox->tx_id);
+		return false;
+	}
+
+	if (readl_relaxed(base + p->reg_val) & BIT(mbox->tx_id)) {
+		dev_warn(mdev->dev, "Mbox: %d, inst: %x, chan: %x not ready\n",
+			mdev->id, mbox->tx_inst, mbox->tx_id);
+		return false;
+	}
+
+	return true;
+}
+
+static bool sti_mbox_tx_is_done(struct mbox_chan *chan)
+{
+	return sti_mbox_tx_is_ready(chan);
+}
+
+static int sti_mbox_send_data(struct mbox_chan *chan, void *data)
+{
+	struct sti_mbox_dev_data *mbox = chan->con_priv;
+	struct sti_mbox_data *md = &mbox->mdata;
+	struct sti_mbox_device *mdev = mbox->parent;
+	struct sti_mbox_attribute *p = mdev->cfg;
+	void __iomem *base;
+
+	dev_info(mdev->dev, "Using Mbox (%x) %s: channel (%d)\n",
+		 mdev->id, mdev->name, mbox->chan_id);
+
+	base = mdev->mbox_reg_base + (p->num_inst * mbox->tx_inst);
+
+	if ((!data) || (!sti_mbox_chan_is_tx(mbox)))
+		return -EINVAL;
+
+	if (sti_mbox_tx_is_ready(chan)) {
+		if (md->tx_addr != NULL)
+			sti_mbox_write(mbox, data);
+
+		/* send event */
+		writel_relaxed(BIT(mbox->tx_id), base + p->reg_set);
+		return 0;
+	}
+
+	return -EBUSY;
+}
+
+static struct mbox_chan_ops sti_mbox_ops = {
+	.startup	= sti_mbox_startup,
+	.send_data	= sti_mbox_send_data,
+	.shutdown	= sti_mbox_shutdown,
+	.last_tx_done	= sti_mbox_tx_is_done,
+};
+
+/*
+ * Interrupt management
+ *
+ * mask/unmask must be managed by SW
+ */
+static void mbox_irq_enable(struct irq_data *d)
+{
+	struct sti_mbox_instance *mbinst =
+		(struct sti_mbox_instance *)d->domain->host_data;
+
+	sti_mbox_enable_irq(mbinst, BIT(d->hwirq));
+}
+
+static void mbox_irq_disable(struct irq_data *d)
+{
+	struct sti_mbox_instance *mbinst =
+		(struct sti_mbox_instance *)d->domain->host_data;
+
+	sti_mbox_disable_irq(mbinst, BIT(d->hwirq));
+}
+
+static struct irq_chip sti_mbox_irq_chip = {
+	.name		= "sti_mbox",
+	.irq_enable	= mbox_irq_enable,
+	.irq_disable	= mbox_irq_disable,
+	.irq_mask	= mbox_irq_disable,
+	.irq_unmask	= mbox_irq_enable,
+};
+
+static int sti_mbox_irq_map(struct irq_domain *d, unsigned int irq,
+			    irq_hw_number_t hwirq)
+{
+	irq_set_chip_and_handler(irq, &sti_mbox_irq_chip,
+				 handle_simple_irq);
+	set_irq_flags(irq, IRQF_VALID);
+
+	return 0;
+}
+
+static const struct irq_domain_ops sti_mbox_irq_ops = {
+	.map    = sti_mbox_irq_map,
+	.xlate  = irq_domain_xlate_onecell,
+};
+
+static const struct sti_mbox_attribute mbox_config_407 = {
+	.num_inst	= 4,
+	.num_mbox	= 32,
+	.reg_set	= REG_MBOX_INT_STA_SET,
+	.reg_clr	= REG_MBOX_INT_STA_CLR,
+	.reg_val	= REG_MBOX_INT_STA_VAL,
+	.reg_ena_set	= REG_MBOX_ENA_SET,
+	.reg_ena_val	= REG_MBOX_ENA_VAL,
+	.reg_ena_clr	= REG_MBOX_ENA_CLR,
+};
+
+static const struct of_device_id sti_mailbox_match[] = {
+	{
+		.compatible = "st,stih407-mailbox",
+		.data = (void *)&mbox_config_407
+	},
+	{ }
+};
+
+static int sti_mbox_map_tx_to_rx(struct platform_device *pdev,
+				 struct sti_mbox_device *mdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	u32 id;
+	int ret;
+
+	mdev->mdev_rx = devm_kzalloc(&pdev->dev, sizeof(struct sti_mbox_device),
+				     GFP_KERNEL);
+	if (!mdev->mdev_rx)
+		return -ENOMEM;
+
+	ret = of_property_read_u32(np, "st,mbox-rx-id", &id);
+	if (!ret) {
+		mdev->rx_id = id;
+		mdev->mdev_rx =  &mdev_rxs[mdev->rx_id];
+	} else
+		mdev->rx_id = MBOX_NO_RX;
+
+	return 0;
+}
+
+static int sti_mbox_create_chan_ctrl(struct platform_device *pdev,
+				     struct sti_mbox_device *mdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct sti_mbox_attribute *p = mdev->cfg;
+	struct sti_mbox_dev_data *mbox;
+	struct mbox_chan *chans;
+	struct sti_mbox_instance *mbinst;
+	const char *name;
+	const __be32 *tmp;
+	const __be32 *mbox_chans;
+	int i, ret, data_len, mb_count = 0;
+
+	of_property_read_string(np, "st,name", &name);
+	strcpy(mdev->name, name);
+
+	/* In case of TX mailbox affect an RX mailbox if needed  */
+	ret = sti_mbox_map_tx_to_rx(pdev, mdev);
+	if (ret)
+		return ret;
+
+	/* Check mailbox configuration from DT */
+	mb_count = of_property_count_strings(np, "st,mbox-names");
+	if (!mb_count || mb_count > p->num_mbox) {
+		dev_err(&pdev->dev,
+			"Wrong number [%d/%d] of mbox devices found\n",
+			mb_count, p->num_mbox);
+		return -ENODEV;
+	}
+
+	chans = devm_kzalloc(&pdev->dev,
+			     (mb_count + 1) * sizeof(struct mbox_chan),
+			     GFP_KERNEL);
+	if (!chans)
+		return -ENOMEM;
+
+	mbox = devm_kzalloc(&pdev->dev,
+			    mb_count * sizeof(struct sti_mbox_dev_data),
+			    GFP_KERNEL);
+	if (!mbox)
+		return -ENOMEM;
+
+	mbox_chans = of_get_property(np, "st,mbox-chans", &data_len);
+	if (!mbox_chans) {
+		dev_err(&pdev->dev, "no mbox device data found\n");
+		return -ENODEV;
+	}
+
+	for (i = 0; i < mb_count; i++) {
+		tmp = mbox_chans + i;
+		mbox->rx_id = (u32)of_read_number(tmp, 1);
+		mbox->rx_inst = (u32)of_read_number(tmp+1, 1);
+		mbox->tx_id = (u32)of_read_number(tmp+2, 1);
+		mbox->tx_inst = (u32)of_read_number(tmp+3, 1);
+
+		/* Affect Rx configuration to the channel if needed */
+		if (sti_mbox_chan_is_rx(mbox)) {
+			if (mdev->rx_id == MBOX_NO_RX) {
+				dev_err(&pdev->dev, "Mbox Rx id not defined for Mailbox: %s\n"
+					, mdev->name);
+				return -EINVAL;
+			}
+
+			mbinst = mdev->mdev_rx->mbinst[mbox->rx_inst];
+
+			if (!mbinst)
+				return -EINVAL;
+
+			if (!mbinst->irq_domain)
+				return -EINVAL;
+
+			mbox->irq = irq_create_mapping(mbinst->irq_domain,
+						       mbox->rx_id);
+			sti_mbox_disable_irq(mbinst, BIT(mbox->rx_id));
+			sti_mbox_clr_irq(mbinst, BIT(mbox->rx_id));
+		}
+		/*
+		 * read here rx_id and fill mbox->instance accordly to what
+		 * we have registered.
+		 */
+		mbox->parent = mdev;
+		mbox->chan_id = i;
+		chans[i].con_priv = (struct sti_mbox_dev_data *)mbox;
+	}
+	mdev->dev = &pdev->dev;
+
+	/* sti mailbox does not have a Tx-Done or Tx-Ready IRQ */
+	mdev->controller.txdone_irq = false;
+	mdev->controller.txdone_poll = true;
+	mdev->controller.txpoll_period = 1000;
+	mdev->controller.ops = &sti_mbox_ops;
+	mdev->controller.chans = chans;
+	mdev->controller.num_chans = mb_count;
+	mdev->controller.dev = mdev->dev;
+
+	ret = mbox_controller_register(&mdev->controller);
+	if (ret)
+		return ret;
+
+	dev_info(&pdev->dev, "Mbox (%x) %s: %x channel registered\n", mdev->id,
+		 mdev->name, mb_count);
+
+	return 0;
+}
+
+static int sti_mbox_create_mbinst(struct platform_device *pdev,
+				  struct sti_mbox_device *mdev,
+				  struct sti_mbox_instance *mbinst)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct sti_mbox_attribute *p = mdev->cfg;
+
+	mbinst->parent = mdev;
+
+	mbinst->irq_domain = irq_domain_add_linear(np, p->num_mbox,
+						   &sti_mbox_irq_ops, mbinst);
+
+	if (!mbinst->irq_domain) {
+		dev_err(&pdev->dev, "Failed to create irqdomain\n");
+		return -ENOSYS;
+	}
+
+	return 0;
+}
+
+static int sti_mbox_create_rx_interrupt(struct platform_device *pdev,
+					struct sti_mbox_device *mdev)
+{
+	struct sti_mbox_instance *mbinst = NULL;
+	struct sti_mbox_attribute *p = mdev->cfg;
+	int ret, i;
+
+	mdev->irq = platform_get_irq(pdev, 0);
+	ret = devm_request_irq(&pdev->dev, mdev->irq, sti_mbox_irq_handler,
+			       IRQF_NO_SUSPEND | IRQF_ONESHOT,	"sti_mbox",
+			       mdev);
+	if (ret)
+		return -EINVAL;
+
+	/*
+	 *  create 4 irq domain per RX Hw Mailbox. Corespond to 4 HW
+	 *  instances
+	 */
+	for (i = 0; i < p->num_inst; i++) {
+		mbinst = devm_kzalloc(&pdev->dev, p->num_inst * sizeof(*mbinst),
+				      GFP_KERNEL);
+		if (!mbinst)
+			return -ENOMEM;
+
+		ret = sti_mbox_create_mbinst(pdev, mdev, mbinst);
+		if (ret)
+			return ret;
+
+		mbinst->id = i;
+
+		mdev->mbinst[i] = mbinst;
+	}
+
+	/* Fill potential Rx mailboxes */
+	mdev_rxs[mdev->id] = *mdev;
+
+	return 0;
+}
+
+static int sti_mbox_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct resource *mem;
+	struct sti_mbox_device *mdev;
+	struct sti_mbox_attribute *cfg;
+	int ret;
+
+	mdev = devm_kzalloc(&pdev->dev, sizeof(struct sti_mbox_device),
+			    GFP_KERNEL);
+	if (!mdev)
+		return -ENOMEM;
+
+	cfg = (struct sti_mbox_attribute *)of_match_device(sti_mailbox_match,
+							   &pdev->dev)->data;
+	if (!cfg) {
+		/* No mailbox configuration */
+		dev_err(&pdev->dev, "No configuration found\n");
+		return -ENODEV;
+	}
+	mdev->cfg = cfg;
+	mdev->id = of_alias_get_id(np, "mailbox");
+	if (mdev->id < 0) {
+		dev_err(&pdev->dev, "No alias found\n");
+		return mdev->id;
+	}
+
+	mem = platform_get_resource_byname(pdev, IORESOURCE_MEM, "mbox-reg");
+	if (!mem)
+		return -ENOENT;
+	if (!devm_request_mem_region(&pdev->dev, mem->start, resource_size(mem),
+				     pdev->name))
+		return -EBUSY;
+	mdev->mbox_reg_base = devm_ioremap(&pdev->dev, mem->start,
+					   resource_size(mem));
+	if (!mdev->mbox_reg_base)
+		return -ENOMEM;
+
+	/* Register interrupt if mailbox is Rx capable */
+	if (of_property_read_bool(np, "st,mbox-rx")) {
+		ret = sti_mbox_create_rx_interrupt(pdev, mdev);
+		if (ret)
+			return ret;
+	}
+
+	/*  Create channels */
+	ret = sti_mbox_create_chan_ctrl(pdev, mdev);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, mdev);
+
+	return 0;
+}
+
+static int sti_mbox_remove(struct platform_device *pdev)
+{
+	struct sti_mbox_device *mdev = platform_get_drvdata(pdev);
+
+	mbox_controller_unregister(&mdev->controller);
+
+	return 0;
+}
+
+static struct platform_driver sti_mbox_driver = {
+	.probe = sti_mbox_probe,
+	.remove = sti_mbox_remove,
+	.driver = {
+		.name = "sti-mailbox",
+		.of_match_table = sti_mailbox_match,
+	},
+};
+
+static int __init sti_mbox_init(void)
+{
+	return platform_driver_register(&sti_mbox_driver);
+}
+
+static void __exit sti_mbox_exit(void)
+{
+	platform_driver_unregister(&sti_mbox_driver);
+}
+
+postcore_initcall(sti_mbox_init);
+module_exit(sti_mbox_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("stmicroelectronics mailbox: st architecture specific functions");
+MODULE_AUTHOR("Alexandre Torgue <alexandre.torgue@st.com>");
+MODULE_AUTHOR("Olivier Lebreton <olivier.lebreton@st.com>");
+MODULE_AUTHOR("Loic Pallardy <loic.pallardy@st.com>");
+MODULE_ALIAS("platform:sti-mailbox");
diff --git a/include/linux/mailbox_sti.h b/include/linux/mailbox_sti.h
new file mode 100644
index 0000000..ff19d07
--- /dev/null
+++ b/include/linux/mailbox_sti.h
@@ -0,0 +1,128 @@
+/*
+ * mailbox-sti.h
+ *
+ * Copyright (C) 2014 ST Microelectronics
+ *
+ * Author:  <olivier.lebreton@st.com> for ST Microelectronics
+ * Author:  <alexandre.torgue@st.com> for ST Microelectronics
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/ioport.h>
+#include <linux/mailbox_controller.h>
+
+/* Max instance per HW mailbox */
+#define MBOX_INST_MAX		4
+
+/*
+ * struct sti_mbox_msg - sti mailbox message description
+ * @dsize:		data payload size
+ * @pdata:		message data payload
+ */
+struct sti_mbox_msg {
+	u32		dsize;
+	u8		*pdata;
+};
+
+/*
+ * struct sti_mbox_attribute - sti mailbox device attribute info
+ * @num_inst:		maximum number of instance in one HW mailbox
+ * @num_mbox:		maximum number of channel per instance
+ * @reg_set:		register offset to generate mailbox interrupt
+ * @reg_clr:		register offset to clear pending interrupt
+ * @reg_val:		register offset to read interrupt status
+ * @reg_ena_set:	register offset to enable mailbox
+ * @reg_ena_val:	register offset to read enable status
+ * @reg_ena_clr:	register offset to disable mailbox
+ */
+struct sti_mbox_attribute {
+	int		num_inst;
+	int		num_mbox;
+	int		reg_set;
+	int		reg_clr;
+	int		reg_val;
+	int		reg_ena_val;
+	int		reg_ena_set;
+	int		reg_ena_clr;
+};
+
+/*
+ * struct sti_mbox_data - sti mailbox buffer attribute info
+ * @rx_offset:		rx mailbox addr in shared memory
+ * @tx_offset:		tx mailbox addr in shared memory
+ */
+struct sti_mbox_data {
+	void __iomem	*rx_addr;
+	void __iomem	*tx_addr;
+};
+
+/*
+ * struct sti_mbox_dev_data - sti channel info
+ * An IP mailbox is composed by 4 instances.
+ * Each instance is composed by 32 channels (also named mbox)
+ * This means that we have potentially 128 channels (128 sw interrupts).
+ * A channel an be used for TX way, RX way or both.
+ *
+ * @mdata:		mailbox buffer info
+ * @parent:		mailbox device to which it is attached
+ * @msg:		rx message
+ * @chan_id:		channel id in an instance
+ * @irq:		irq number (virtual) assigned to the channel
+ * @rx_inst:		instance for the channel used in RX way
+ * @rx_id:		id in an instance for the channel used in RX way
+ * @tx_inst:		instance for the channel used in TX way
+ * @tx_id:		id in an instance for the channel used in TX way
+ */
+struct sti_mbox_dev_data {
+	struct sti_mbox_data		mdata;
+	struct sti_mbox_device		*parent;
+	struct sti_mbox_msg		*msg;
+	u32				chan_id;
+	u32				irq;
+	u32				rx_inst;
+	u32				rx_id;
+	u32				tx_inst;
+	u32				tx_id;
+};
+
+struct sti_mbox_instance {
+	struct irq_domain	*irq_domain;
+	struct sti_mbox_device	*parent;
+	u32			irq_msk;
+	int			id;
+};
+
+/*
+ * struct sti_mbox_device - sti mailbox device data
+ * An IP mailbox is composed by 4 instances.
+ * Each instance is composed by 32 channels (also named mbox)
+ * This means that we have potentially 128 channels (128 sw interrupts).
+ * A channel an be used for TX way, RX way or both.
+ *
+ * @id:			Id of the mailbox
+ * @irq:		Interrupt number assigned to mailbox Rx
+ * @cfg:		mailbox attribute data
+ * @dev:		device to which it is attached
+ * @mbox_reg_base:	base address of the register mapping region
+ * @controller:		representation of a communication channel controller
+ * @type:		type of mailbox (tx, rx or rx_tx)
+ * @name:		name of the mailbox
+ * @mbox_inst		data for several instances in the mailbox
+ */
+struct sti_mbox_device {
+	int				id;
+	int				irq;
+	struct sti_mbox_attribute	*cfg;
+	struct device			*dev;
+	void __iomem			*mbox_reg_base;
+	struct mbox_controller		controller;
+	const char			*type;
+	struct sti_mbox_device		*mdev_rx;
+	u32				rx_id;
+	char				name[64];
+	struct sti_mbox_instance	*mbinst[MBOX_INST_MAX];
+};
-- 
1.9.1

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Arnd Bergmann]

On Tuesday 03 March 2015 10:41:23 Lee Jones wrote:
> +
> +/*
> + * struct sti_mbox_msg - sti mailbox message description
> + * @dsize:             data payload size
> + * @pdata:             message data payload
> + */
> +struct sti_mbox_msg {
> +       u32             dsize;
> +       u8              *pdata;
> +};

As mentioned in another thread, we may just want to add a 'size'
argument to the message send function, and a default helper for
messages with size of 32 bits.

I don't think it's good to fragment this further by adding
an indirect message interface in a particular driver.

	Arnd

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Jassi Brar]

On 3 March 2015 at 17:04, Arnd Bergmann <arnd@arndb.de> wrote:
> On Tuesday 03 March 2015 10:41:23 Lee Jones wrote:
>> +
>> +/*
>> + * struct sti_mbox_msg - sti mailbox message description
>> + * @dsize:             data payload size
>> + * @pdata:             message data payload
>> + */
>> +struct sti_mbox_msg {
>> +       u32             dsize;
>> +       u8              *pdata;
>> +};
>
> As mentioned in another thread, we may just want to add a 'size'
> argument to the message send function, and a default helper for
> messages with size of 32 bits.
>
Case-a) 'size' is a member of the payload structure itself
    The extra 'size' argument would only be used for sanity check.
    This driver seems so. Lee, can you not do without 'dsize'?

Case-b) 'size' is not a member of payload structure:
     b1)  payload is fixed length, that is 'size' := sizeof(struct my_payload)
            Here the size argument is redundant.

     b2)  payload length varies
            This case is highly unlikely because there would be no way
for remote to know how many bytes to read as the payload. Not to mean
we can't do without the 'size' argument.

Your opinion has huge weight, but I would like to be enlightened
before agreeing.

> I don't think it's good to fragment this further by adding
> an indirect message interface in a particular driver.
>
For example, I am reading this again and again without getting it.

Thanks
Jassi

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Jassi Brar]

On 3 March 2015 at 16:11, Lee Jones <lee.jones@linaro.org> wrote:

> ---
>  drivers/mailbox/Kconfig       |   7 +
>  drivers/mailbox/Makefile      |   2 +
>  drivers/mailbox/mailbox-sti.c | 664 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/mailbox_sti.h   | 128 ++++++++
>
How about the header in include/linux/soc/sti/  away from the limelight?

> + */
> +#define MBOX_HW_MAX            5
> +#define MBOX_NO_RX             0xff
> +
> +static struct sti_mbox_device mdev_rxs[MBOX_HW_MAX];
> +
> +static DEFINE_SPINLOCK(sti_mbox_irqs_lock);
> +
> +/* Mailbox H/W preparations */
> +static struct irq_chip sti_mbox_irq_chip;
> +
> +static inline bool sti_mbox_chan_is_rx(struct sti_mbox_dev_data *mbox)
> +{
> +       return ((mbox->rx_id != MBOX_NO_RX) && (mbox->rx_inst != MBOX_NO_RX));
> +}
> +
> +static inline bool sti_mbox_chan_is_tx(struct sti_mbox_dev_data *mbox)
> +{
> +       return ((mbox->tx_id != MBOX_NO_RX) && (mbox->tx_inst != MBOX_NO_RX));
>
  nit:  something neutral like MBOX_ABSENT or anything without RX?

> +/* Message management */
> +static void sti_mbox_read(struct sti_mbox_dev_data *mbox,
> +                         struct sti_mbox_msg *msg)
> +{
> +       struct sti_mbox_data *md = &mbox->mdata;
> +       void __iomem *hdr = md->rx_addr;
> +
> +       /* Read data payload */
> +       msg->dsize = readb(hdr);
> +       msg->pdata = (u8*)++hdr;
> +}
> +
> +static void sti_mbox_write(struct sti_mbox_dev_data *mbox, void *data)
> +{
> +       struct sti_mbox_data *md = &mbox->mdata;
> +       struct sti_mbox_msg *msg = (struct sti_mbox_msg *)data;
> +       u32 len = msg->dsize;
> +       void __iomem *hdr;
> +       u8 *wrb;
> +       unsigned int j;
> +
> +       hdr = md->tx_addr;
> +
> +       /* Payload size */
> +       writeb((u8)len, hdr);
>
So the first 1byte bitfield is the 'size' of the packset. could you
please get rid of sti_mbox_msg.dsize?

> +
> +       wrb = msg->pdata;
> +       if (!wrb)
> +               return;
> +
> +       /* Payload data */
> +       for (j = 0, hdr++; j < len; j++, wrb++, hdr++)
> +               writeb(*wrb, hdr);
> +}
> +
> +/* Mailbox IRQ handle functions */
> +static void sti_mbox_enable_irq(struct sti_mbox_instance *mbinst, u32 msk)
> +{
> +       struct sti_mbox_device *mdev = mbinst->parent;
> +       struct sti_mbox_attribute *p = mdev->cfg;
> +       void __iomem *base;
> +       unsigned long flags;
> +
> +       base = mdev->mdev_rx->mbox_reg_base + (mbinst->id * p->num_inst);
> +       spin_lock_irqsave(&sti_mbox_irqs_lock, flags);
> +       mbinst->irq_msk |= msk;
> +
> +       writel_relaxed(msk, base + p->reg_ena_set);
> +
> +       spin_unlock_irqrestore(&sti_mbox_irqs_lock, flags);
> +}
> +
> +static void sti_mbox_disable_irq(struct sti_mbox_instance *mbinst, u32 msk)
> +{
> +       struct sti_mbox_device *mdev = mbinst->parent;
> +       struct sti_mbox_attribute *p = mdev->cfg;
> +       void __iomem *base;
> +       unsigned long flags;
> +
> +       base = mdev->mdev_rx->mbox_reg_base + (mbinst->id * p->num_inst);
> +       spin_lock_irqsave(&sti_mbox_irqs_lock, flags);
> +       mbinst->irq_msk &= ~msk;
> +       writel_relaxed(msk, base + p->reg_ena_clr);
> +       spin_unlock_irqrestore(&sti_mbox_irqs_lock, flags);
> +}
> +
> +static void sti_mbox_clr_irq(struct sti_mbox_instance *mbinst, u32 msk)
> +{
> +       struct sti_mbox_device *mdev = mbinst->parent;
> +       struct sti_mbox_attribute *p = mdev->cfg;
> +       void __iomem *base;
> +
> +       base = mdev->mdev_rx->mbox_reg_base + (mbinst->id * p->num_inst);
> +       writel_relaxed(msk, base + p->reg_clr);
> +}
> +
> +static irqreturn_t sti_mbox_thread_interrupt(int irq, void *data)
> +{
> +       struct mbox_chan *chan = data;
> +       struct sti_mbox_dev_data *mbox = chan->con_priv;
> +       struct sti_mbox_device *mdev_rx = mbox->parent->mdev_rx;
> +
> +       mbox_chan_received_data(chan, (void *)mbox->msg);
> +       sti_mbox_enable_irq(mdev_rx->mbinst[mbox->rx_inst], BIT(mbox->rx_id));
> +
> +       return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t sti_mbox_interrupt(int irq, void *data)
> +{
> +       struct mbox_chan *chan = data;
> +       struct sti_mbox_dev_data *mbox = chan->con_priv;
> +       struct sti_mbox_data *md = &mbox->mdata;
> +       struct sti_mbox_device *mdev_rx = mbox->parent->mdev_rx;
> +
> +       sti_mbox_disable_irq(mdev_rx->mbinst[mbox->rx_inst], BIT(mbox->rx_id));
> +
> +       if (md->rx_addr != NULL)
> +               sti_mbox_read(mbox, mbox->msg);
> +
> +       return IRQ_WAKE_THREAD;
> +}
> +
> +
> +static irqreturn_t sti_mbox_irq_handler(int irq, void *data)
> +{
> +       struct sti_mbox_device *mdev_rx = data;
> +       struct sti_mbox_attribute *p = mdev_rx->cfg;
> +       struct irq_domain *mbox_irq_domain;
> +       void __iomem *base;
> +       u32 irq_chan;
> +       unsigned long bits = 0;
> +       u8 n;
> +       int i;
> +
> +       base = mdev_rx->mbox_reg_base + mdev_rx->cfg->reg_val;
> +
> +       for (i = 0; i < p->num_inst; i++) {
> +               bits = readl_relaxed(base + (i * p->num_inst));
> +               if (bits)
> +                       break;
> +       }
> +
> +       if (unlikely(!bits))
> +               return IRQ_NONE;
> +
> +       mbox_irq_domain = mdev_rx->mbinst[i]->irq_domain;
> +
> +       for (n = 0; bits; n++) {
> +               if (test_and_clear_bit(n, &bits)) {
> +
> +                       irq_chan = irq_find_mapping(mbox_irq_domain, n);
> +                       if (mdev_rx->mbinst[i]->irq_msk & BIT(n)) {
> +                               generic_handle_irq(irq_chan);
> +                               sti_mbox_clr_irq(mdev_rx->mbinst[i], BIT(n));
> +
> +                       } else
> +                               dev_warn(mdev_rx->dev,
> +                                        "Unexpected mailbox interrupt\n"
> +                                        "mask: %x\n",
> +                                        mdev_rx->mbinst[i]->irq_msk);
> +               }
> +       }
> +       return IRQ_HANDLED;
> +}
> +
> +/* Channel management */
> +static int sti_mbox_startup(struct mbox_chan *chan)
> +{
> +       struct sti_mbox_dev_data *mbox = chan->con_priv;
> +       struct sti_mbox_device *mdev = mbox->parent;
> +       char name[32];
> +       int ret = 0;
> +
> +       /* Allocate Rx msg per channel */
> +       mbox->msg = devm_kzalloc(mdev->dev, sizeof(struct sti_mbox_device),
> +                                 GFP_KERNEL);
> +       if (!mbox->msg)
> +               return -ENOMEM;
> +
> +       if (sti_mbox_chan_is_rx(mbox)) {
> +               snprintf(name, sizeof(name), "%s-%d", mdev->name,
> +                        mbox->chan_id);
> +               /* IRQ automatically enabled */
> +               ret = request_threaded_irq(mbox->irq, sti_mbox_interrupt,
> +                                          sti_mbox_thread_interrupt,
> +                                          IRQF_SHARED, name, chan);
> +               if (ret)
> +                       dev_err(mdev->dev,
> +                               "failed to register mailbox interrupt:%d\n",
> +                               ret);
> +       }
> +
> +       return ret;
> +}
> +
> +static void sti_mbox_shutdown(struct mbox_chan *chan)
> +{
> +       struct sti_mbox_dev_data *mbox = chan->con_priv;
> +       struct sti_mbox_device *mdev = mbox->parent;
> +
> +       /* IRQ automatically disabled */
> +       free_irq(mbox->irq, chan);
> +
> +       /* Free Rx msg */
> +       devm_kfree(mdev->dev, mbox->msg);
> +}
> +
> +static bool sti_mbox_tx_is_ready(struct mbox_chan *chan)
> +{
> +       struct sti_mbox_dev_data *mbox = chan->con_priv;
> +       struct sti_mbox_device *mdev = mbox->parent;
> +       struct sti_mbox_attribute *p = mdev->cfg;
> +       void __iomem *base;
> +
> +       /*
> +        *  Check if tx mbox has got a pending interrupt, and if it is enabled
> +        *  before sending a new message
> +        */
> +       base = mdev->mbox_reg_base + (p->num_inst * mbox->tx_inst);
> +
> +       if (!(readl_relaxed(base + p->reg_ena_val) & BIT(mbox->tx_id))) {
> +               dev_warn(mdev->dev, "Mbox: %d, inst: %x, chan: %x disabled\n",
> +                       mdev->id, mbox->tx_inst, mbox->tx_id);
> +               return false;
> +       }
> +
> +       if (readl_relaxed(base + p->reg_val) & BIT(mbox->tx_id)) {
> +               dev_warn(mdev->dev, "Mbox: %d, inst: %x, chan: %x not ready\n",
> +                       mdev->id, mbox->tx_inst, mbox->tx_id);
> +               return false;
> +       }
> +
> +       return true;
> +}
> +
> +static bool sti_mbox_tx_is_done(struct mbox_chan *chan)
> +{
> +       return sti_mbox_tx_is_ready(chan);
> +}
Why not simply move sti_mbox_tx_is_ready -> sti_mbox_tx_is_done ?

> +
> +static int sti_mbox_send_data(struct mbox_chan *chan, void *data)
> +{
> +       struct sti_mbox_dev_data *mbox = chan->con_priv;
> +       struct sti_mbox_data *md = &mbox->mdata;
> +       struct sti_mbox_device *mdev = mbox->parent;
> +       struct sti_mbox_attribute *p = mdev->cfg;
> +       void __iomem *base;
> +
> +       dev_info(mdev->dev, "Using Mbox (%x) %s: channel (%d)\n",
> +                mdev->id, mdev->name, mbox->chan_id);
> +
> +       base = mdev->mbox_reg_base + (p->num_inst * mbox->tx_inst);
> +
> +       if ((!data) || (!sti_mbox_chan_is_tx(mbox)))
>
nit: too much protection.

> +               return -EINVAL;
> +
> +       if (sti_mbox_tx_is_ready(chan)) {
.send_data() isn't called, unless last_tx_done(). So you may drop the check


> +
> +       mbox_chans = of_get_property(np, "st,mbox-chans", &data_len);
> +       if (!mbox_chans) {
> +               dev_err(&pdev->dev, "no mbox device data found\n");
> +               return -ENODEV;
> +       }
> +
> +       for (i = 0; i < mb_count; i++) {
> +               tmp = mbox_chans + i;
> +               mbox->rx_id = (u32)of_read_number(tmp, 1);
> +               mbox->rx_inst = (u32)of_read_number(tmp+1, 1);
> +               mbox->tx_id = (u32)of_read_number(tmp+2, 1);
> +               mbox->tx_inst = (u32)of_read_number(tmp+3, 1);
nit:   some spaces and
  of_property_read_u32_index(np, "st,mbox-chans", 0, &mbox->rx_id)
  of_property_read_u32_index(np, "st,mbox-chans", 1, &mbox->rx_inst)
  of_property_read_u32_index(np, "st,mbox-chans", 2, &mbox->tx_id)
  of_property_read_u32_index(np, "st,mbox-chans", 3, &mbox->tx_inst)  ?


> +
> +               /* Affect Rx configuration to the channel if needed */
> +               if (sti_mbox_chan_is_rx(mbox)) {
> +                       if (mdev->rx_id == MBOX_NO_RX) {
> +                               dev_err(&pdev->dev, "Mbox Rx id not defined for Mailbox: %s\n"
> +                                       , mdev->name);
> +                               return -EINVAL;
> +                       }
> +
> +                       mbinst = mdev->mdev_rx->mbinst[mbox->rx_inst];
> +
> +                       if (!mbinst)
> +                               return -EINVAL;
> +
> +                       if (!mbinst->irq_domain)
> +                               return -EINVAL;
> +
> +                       mbox->irq = irq_create_mapping(mbinst->irq_domain,
> +                                                      mbox->rx_id);
>
simply assigning same IRQ to all controller DT nodes and using
IRQF_SHARED for the common handler, wouldn't work?


> +                       sti_mbox_disable_irq(mbinst, BIT(mbox->rx_id));
> +                       sti_mbox_clr_irq(mbinst, BIT(mbox->rx_id));
> +               }
> +               /*
> +                * read here rx_id and fill mbox->instance accordly to what
> +                * we have registered.
> +                */
> +               mbox->parent = mdev;
> +               mbox->chan_id = i;
> +               chans[i].con_priv = (struct sti_mbox_dev_data *)mbox;
>
isn't mbox already a struct sti_mbox_dev_data *


> +       }
> +       mdev->dev = &pdev->dev;
> +
> +       /* sti mailbox does not have a Tx-Done or Tx-Ready IRQ */
> +       mdev->controller.txdone_irq = false;
> +       mdev->controller.txdone_poll = true;
> +       mdev->controller.txpoll_period = 1000;
>
does your remote really take ~1sec to respond?


> +++ b/include/linux/mailbox_sti.h
> @@ -0,0 +1,128 @@
> +/*
> + * mailbox-sti.h
> + *
> + * Copyright (C) 2014 ST Microelectronics
> + *
> + * Author:  <olivier.lebreton@st.com> for ST Microelectronics
> + * Author:  <alexandre.torgue@st.com> for ST Microelectronics
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#include <linux/ioport.h>
> +#include <linux/mailbox_controller.h>
> +
> +/* Max instance per HW mailbox */
> +#define MBOX_INST_MAX          4
> +
> +/*
> + * struct sti_mbox_msg - sti mailbox message description
> + * @dsize:             data payload size
> + * @pdata:             message data payload
> + */
> +struct sti_mbox_msg {
> +       u32             dsize;
> +       u8              *pdata;
> +};
> +
> +/*
> + * struct sti_mbox_attribute - sti mailbox device attribute info
> + * @num_inst:          maximum number of instance in one HW mailbox
> + * @num_mbox:          maximum number of channel per instance
> + * @reg_set:           register offset to generate mailbox interrupt
> + * @reg_clr:           register offset to clear pending interrupt
> + * @reg_val:           register offset to read interrupt status
> + * @reg_ena_set:       register offset to enable mailbox
> + * @reg_ena_val:       register offset to read enable status
> + * @reg_ena_clr:       register offset to disable mailbox
> + */
> +struct sti_mbox_attribute {
> +       int             num_inst;
> +       int             num_mbox;
> +       int             reg_set;
> +       int             reg_clr;
> +       int             reg_val;
> +       int             reg_ena_val;
> +       int             reg_ena_set;
> +       int             reg_ena_clr;
> +};
> +
> +/*
> + * struct sti_mbox_data - sti mailbox buffer attribute info
> + * @rx_offset:         rx mailbox addr in shared memory
> + * @tx_offset:         tx mailbox addr in shared memory
> + */
> +struct sti_mbox_data {
> +       void __iomem    *rx_addr;
> +       void __iomem    *tx_addr;
> +};
> +
> +/*
> + * struct sti_mbox_dev_data - sti channel info
> + * An IP mailbox is composed by 4 instances.
> + * Each instance is composed by 32 channels (also named mbox)
> + * This means that we have potentially 128 channels (128 sw interrupts).
> + * A channel an be used for TX way, RX way or both.
> + *
> + * @mdata:             mailbox buffer info
> + * @parent:            mailbox device to which it is attached
> + * @msg:               rx message
> + * @chan_id:           channel id in an instance
> + * @irq:               irq number (virtual) assigned to the channel
> + * @rx_inst:           instance for the channel used in RX way
> + * @rx_id:             id in an instance for the channel used in RX way
> + * @tx_inst:           instance for the channel used in TX way
> + * @tx_id:             id in an instance for the channel used in TX way
> + */
> +struct sti_mbox_dev_data {
> +       struct sti_mbox_data            mdata;
> +       struct sti_mbox_device          *parent;
> +       struct sti_mbox_msg             *msg;
> +       u32                             chan_id;
> +       u32                             irq;
> +       u32                             rx_inst;
> +       u32                             rx_id;
> +       u32                             tx_inst;
> +       u32                             tx_id;
> +};
> +
> +struct sti_mbox_instance {
> +       struct irq_domain       *irq_domain;
> +       struct sti_mbox_device  *parent;
> +       u32                     irq_msk;
> +       int                     id;
> +};
> +
> +/*
> + * struct sti_mbox_device - sti mailbox device data
> + * An IP mailbox is composed by 4 instances.
> + * Each instance is composed by 32 channels (also named mbox)
> + * This means that we have potentially 128 channels (128 sw interrupts).
> + * A channel an be used for TX way, RX way or both.
> + *
> + * @id:                        Id of the mailbox
> + * @irq:               Interrupt number assigned to mailbox Rx
> + * @cfg:               mailbox attribute data
> + * @dev:               device to which it is attached
> + * @mbox_reg_base:     base address of the register mapping region
> + * @controller:                representation of a communication channel controller
> + * @type:              type of mailbox (tx, rx or rx_tx)
> + * @name:              name of the mailbox
> + * @mbox_inst          data for several instances in the mailbox
> + */
> +struct sti_mbox_device {
> +       int                             id;
> +       int                             irq;
> +       struct sti_mbox_attribute       *cfg;
> +       struct device                   *dev;
> +       void __iomem                    *mbox_reg_base;
> +       struct mbox_controller          controller;
> +       const char                      *type;
> +       struct sti_mbox_device          *mdev_rx;
> +       u32                             rx_id;
> +       char                            name[64];
> +       struct sti_mbox_instance        *mbinst[MBOX_INST_MAX];
> +};
>
There isn't any client driver in this patchset to tell exactly, but it
seems the header could be split into one shared between mailbox
clients and provider and another internal to client/provider ?

[PATCH 2/3] mailbox: dt: Supply bindings for ST's Mailbox IP

[Jassi Brar]

On 3 March 2015 at 16:11, Lee Jones <lee.jones@linaro.org> wrote:
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
>  .../devicetree/bindings/mailbox/sti-mailbox.txt    | 66 ++++++++++++++++++++++
>  1 file changed, 66 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mailbox/sti-mailbox.txt
>
> diff --git a/Documentation/devicetree/bindings/mailbox/sti-mailbox.txt b/Documentation/devicetree/bindings/mailbox/sti-mailbox.txt
> new file mode 100644
> index 0000000..c965c13
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/sti-mailbox.txt
> @@ -0,0 +1,66 @@
> +ST Microelectronics Mailbox Driver
> +
> +Required properties:
> +- compatible           : Should be "st,stih407-mailbox"
> +- reg                  : Offset and length of the register set for the device
> +- reg-names            : Should contain the reg name "mbox-reg".
> +- st,name              : Name of the mailbox
> +- st,mbox-chans                : Mbox/channels descriptor data private to each channel.
> +                         The 4 cells represent the following data:
> +                               Cell #1 (rx_id) - rx mbox num in an instance.
> +                               Cell #2 (rx_inst) - rx mbox instance num.
> +                               Cell #3 (tx_id) - tx mbox num in an instance.
> +                               Cell #4 (tx_inst) - tx mbox instance num.
> +
> +                         Note that an IP Mailbox is composed by 4 instances and
> +                         each instance is composed by 32 mailboxes.
> +                         You define here the configuration of a channel (at
> +                         framework level).
>
mbox-cells ?

> +
> +Optional properties
> +- st,mbox-rx           : Indicaties if the mailbox can be used as Rx mailbox.
>
isn't this property implied by the presence of interrupts property,
and hence redundant?

> +- st,mbox-rx-id                : If a Rx mailbox is affected to a Tx mailbox (to have
> +                         full-duplex channel), this field indiactes the Id of
> +                         the Rx mailbox to use.
> +- interrupts           : Contains the IRQ line for a RX mailbox.
> +- interrupt-names      : Should contain the interrupt name.
> +
> +Examples:
> +
> +mailbox0: mailbox at 0 {
> +       compatible = "st,stih407-mailbox";
> +       #address-cells = <1>;
> +       #size-cells = <1>;
> +       #mbox-cells = <1>;
> +       reg = <0x8f00000 0x1000>;
> +       reg-names = "mbox-reg";
> +       interrupts = <GIC_SPI 1 IRQ_TYPE_NONE>;
> +       interrupt-names = "mb0_irq";
> +       st,name = "a9";
> +       st,mbox-rx;
> +       st,mbox-rx-id = <0>;
> +       st,mbox-chans = <0 1 0 1>;
> +};
> +
> +mailbox3: mailbox at 3 {
> +       compatible = "st,stih407-mailbox";
> +       #address-cells = <1>;
> +       #size-cells = <1>;
> +       #mbox-cells = <1>;
> +       reg = <0x8f03000 0x100>;
> +       reg-names = "mbox-reg";
> +       st,name = "st231_video";
> +       st,mbox-rx-id = <0>;
> +       st,mbox-chans = <2 1 2 1>;
> +};
> +
> +In this configuration, if you use channel 0 you will have the following
> +configuration:
> +- "chan0_video" will use mailbox0 as Rx mailbox.
> +- "chan0_video" will use instance 1, bit 2 in mailbox0 for rx.
> +- "chan0_video" will use instance 1, bit 2 in mailbox3 for tx.
> +
> +If you declare a channel only for Rx, you have to set magic number 0xff
> +for tx_id and tx_instance.
> +If you declare a channel only for Tx, you have to set magic number 0xff
> +for rx_id and rx_instance.
>
some client node example would look great here

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Lee Jones]

On Wed, 04 Mar 2015, Jassi Brar wrote:
> On 3 March 2015 at 16:11, Lee Jones <lee.jones@linaro.org> wrote:
> 
> > ---
> >  drivers/mailbox/Kconfig       |   7 +
> >  drivers/mailbox/Makefile      |   2 +
> >  drivers/mailbox/mailbox-sti.c | 664 ++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/mailbox_sti.h   | 128 ++++++++

[...]

> > +static int sti_mbox_send_data(struct mbox_chan *chan, void *data)
> > +{
> > +       struct sti_mbox_dev_data *mbox = chan->con_priv;
> > +       struct sti_mbox_data *md = &mbox->mdata;
> > +       struct sti_mbox_device *mdev = mbox->parent;
> > +       struct sti_mbox_attribute *p = mdev->cfg;
> > +       void __iomem *base;
> > +
> > +       dev_info(mdev->dev, "Using Mbox (%x) %s: channel (%d)\n",
> > +                mdev->id, mdev->name, mbox->chan_id);
> > +
> > +       base = mdev->mbox_reg_base + (p->num_inst * mbox->tx_inst);
> > +
> > +       if ((!data) || (!sti_mbox_chan_is_tx(mbox)))
> >
> nit: too much protection.

What makes you think that?

[...]

> > +                       mbox->irq = irq_create_mapping(mbinst->irq_domain,
> > +                                                      mbox->rx_id);
> >
> simply assigning same IRQ to all controller DT nodes and using
> IRQF_SHARED for the common handler, wouldn't work?

I do have intentions to simplify this driver somewhat, but that will
take some time as it will require a great deal of consultation and
testing from the ST side.  This is the current internal implementation
which is used in the wild and has been fully tested.  If you'll allow
me to conduct my adaptions subsequently we can have full history and a
possible reversion plan if anything untoward take place i.e. I mess
something up.

[...]

> > + * struct sti_mbox_msg - sti mailbox message description
> > + * @dsize:             data payload size
> > + * @pdata:             message data payload
> > + */
> > +struct sti_mbox_msg {
> > +       u32             dsize;
> > +       u8              *pdata;
> > +};
> >
> There isn't any client driver in this patchset to tell exactly, but it
> seems the header could be split into one shared between mailbox
> clients and provider and another internal to client/provider ?

I believe only the above will be required by the client.  Seems silly
to create a client specific header just for that, don't you think?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org ? Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Lee Jones]

On Tue, 03 Mar 2015, Jassi Brar wrote:

> On 3 March 2015 at 17:04, Arnd Bergmann <arnd@arndb.de> wrote:
> > On Tuesday 03 March 2015 10:41:23 Lee Jones wrote:
> >> +
> >> +/*
> >> + * struct sti_mbox_msg - sti mailbox message description
> >> + * @dsize:             data payload size
> >> + * @pdata:             message data payload
> >> + */
> >> +struct sti_mbox_msg {
> >> +       u32             dsize;
> >> +       u8              *pdata;
> >> +};
> >
> > As mentioned in another thread, we may just want to add a 'size'
> > argument to the message send function, and a default helper for
> > messages with size of 32 bits.
> >
> Case-a) 'size' is a member of the payload structure itself
>     The extra 'size' argument would only be used for sanity check.
>     This driver seems so. Lee, can you not do without 'dsize'?
> 
> Case-b) 'size' is not a member of payload structure:
>      b1)  payload is fixed length, that is 'size' := sizeof(struct my_payload)
>             Here the size argument is redundant.
> 
>      b2)  payload length varies
>             This case is highly unlikely because there would be no way
> for remote to know how many bytes to read as the payload. Not to mean
> we can't do without the 'size' argument.
> 
> Your opinion has huge weight, but I would like to be enlightened
> before agreeing.

Let's simplify this.

If you want to have varying length payloads, you have to carry the
size in the payload.  If you wish to force fixed size payloads, then
you may do without a size segment.

Do you really want to force all users of Mailbox to use fixed size
payloads?  That sounds daft to me, as we have no idea how the payload
is being used by the remote processor.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org ? Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Jassi Brar]

On Wed, Mar 18, 2015 at 6:42 PM, Lee Jones <lee.jones@linaro.org> wrote:
> On Wed, 04 Mar 2015, Jassi Brar wrote:
>
>> > +
>> > +       if ((!data) || (!sti_mbox_chan_is_tx(mbox)))
>> >
>> nit: too much protection.
>
> What makes you think that?
>
 Usually we write
               if (!data || !sti_mbox_chan_is_tx(mbox))


>> > +                       mbox->irq = irq_create_mapping(mbinst->irq_domain,
>> > +                                                      mbox->rx_id);
>> >
>> simply assigning same IRQ to all controller DT nodes and using
>> IRQF_SHARED for the common handler, wouldn't work?
>
> I do have intentions to simplify this driver somewhat, but that will
> take some time as it will require a great deal of consultation and
> testing from the ST side.  This is the current internal implementation
> which is used in the wild and has been fully tested.  If you'll allow
> me to conduct my adaptions subsequently we can have full history and a
> possible reversion plan if anything untoward take place i.e. I mess
> something up.
>
OK, but wouldn't that break the bindings of this driver when you
eventually do that?

>> > + * struct sti_mbox_msg - sti mailbox message description
>> > + * @dsize:             data payload size
>> > + * @pdata:             message data payload
>> > + */
>> > +struct sti_mbox_msg {
>> > +       u32             dsize;
>> > +       u8              *pdata;
>> > +};
>> >
>> There isn't any client driver in this patchset to tell exactly, but it
>> seems the header could be split into one shared between mailbox
>> clients and provider and another internal to client/provider ?
>
> I believe only the above will be required by the client.  Seems silly
> to create a client specific header just for that, don't you think?
>
Do you mean to have copies of the structure in controller and client driver? :O

-Jassi

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Jassi Brar]

On Wed, Mar 18, 2015 at 6:47 PM, Lee Jones <lee.jones@linaro.org> wrote:
> On Tue, 03 Mar 2015, Jassi Brar wrote:
>
>> On 3 March 2015 at 17:04, Arnd Bergmann <arnd@arndb.de> wrote:
>> > On Tuesday 03 March 2015 10:41:23 Lee Jones wrote:
>> >> +
>> >> +/*
>> >> + * struct sti_mbox_msg - sti mailbox message description
>> >> + * @dsize:             data payload size
>> >> + * @pdata:             message data payload
>> >> + */
>> >> +struct sti_mbox_msg {
>> >> +       u32             dsize;
>> >> +       u8              *pdata;
>> >> +};
>> >
>> > As mentioned in another thread, we may just want to add a 'size'
>> > argument to the message send function, and a default helper for
>> > messages with size of 32 bits.
>> >
>> Case-a) 'size' is a member of the payload structure itself
>>     The extra 'size' argument would only be used for sanity check.
>>     This driver seems so. Lee, can you not do without 'dsize'?
>>
>> Case-b) 'size' is not a member of payload structure:
>>      b1)  payload is fixed length, that is 'size' := sizeof(struct my_payload)
>>             Here the size argument is redundant.
>>
>>      b2)  payload length varies
>>             This case is highly unlikely because there would be no way
>> for remote to know how many bytes to read as the payload. Not to mean
>> we can't do without the 'size' argument.
>>
>> Your opinion has huge weight, but I would like to be enlightened
>> before agreeing.
>
> Let's simplify this.
>
> If you want to have varying length payloads, you have to carry the
> size in the payload.  If you wish to force fixed size payloads, then
> you may do without a size segment.
>
> Do you really want to force all users of Mailbox to use fixed size
> payloads?
>
No. I only observed the fact that every known mailbox controller
driver already has a way to figure out the payload length because
either the protocol uses fixed length payloads or has the 'size' field
in every payload.
I am yet to see a platform that uses both, then the 'size' argument
will be helpful but still not necessary.

-Jassi

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Lee Jones]

On Wed, 18 Mar 2015, Jassi Brar wrote:
> On Wed, Mar 18, 2015 at 6:42 PM, Lee Jones <lee.jones@linaro.org> wrote:
> > On Wed, 04 Mar 2015, Jassi Brar wrote:
> >
> >> > +
> >> > +       if ((!data) || (!sti_mbox_chan_is_tx(mbox)))
> >> >
> >> nit: too much protection.
> >
> > What makes you think that?
> >
>  Usually we write
>                if (!data || !sti_mbox_chan_is_tx(mbox))

Ah, the parentheses.  Yes, I agree.  Thanks for clarifying.

> >> > +                       mbox->irq = irq_create_mapping(mbinst->irq_domain,
> >> > +                                                      mbox->rx_id);
> >> >
> >> simply assigning same IRQ to all controller DT nodes and using
> >> IRQF_SHARED for the common handler, wouldn't work?
> >
> > I do have intentions to simplify this driver somewhat, but that will
> > take some time as it will require a great deal of consultation and
> > testing from the ST side.  This is the current internal implementation
> > which is used in the wild and has been fully tested.  If you'll allow
> > me to conduct my adaptions subsequently we can have full history and a
> > possible reversion plan if anything untoward take place i.e. I mess
> > something up.
> >
> OK, but wouldn't that break the bindings of this driver when you
> eventually do that?

That's going to happen regardless, since these bindings are already in
use internally.  Mainline (i.e. v4.0+) isn't going to be used in
products for years to come, so we have a lot of time until any new
bindings become ABI.

> >> > + * struct sti_mbox_msg - sti mailbox message description
> >> > + * @dsize:             data payload size
> >> > + * @pdata:             message data payload
> >> > + */
> >> > +struct sti_mbox_msg {
> >> > +       u32             dsize;
> >> > +       u8              *pdata;
> >> > +};
> >> >
> >> There isn't any client driver in this patchset to tell exactly, but it
> >> seems the header could be split into one shared between mailbox
> >> clients and provider and another internal to client/provider ?
> >
> > I believe only the above will be required by the client.  Seems silly
> > to create a client specific header just for that, don't you think?
> >
> Do you mean to have copies of the structure in controller and client driver? :O

I do not.  I planned on sharing the main header with with client
also.

But I guess by your reaction you suggest having a teeny client header
as the best way forward then.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org ? Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Lee Jones]

On Wed, 18 Mar 2015, Jassi Brar wrote:

> On Wed, Mar 18, 2015 at 6:47 PM, Lee Jones <lee.jones@linaro.org> wrote:
> > On Tue, 03 Mar 2015, Jassi Brar wrote:
> >
> >> On 3 March 2015 at 17:04, Arnd Bergmann <arnd@arndb.de> wrote:
> >> > On Tuesday 03 March 2015 10:41:23 Lee Jones wrote:
> >> >> +
> >> >> +/*
> >> >> + * struct sti_mbox_msg - sti mailbox message description
> >> >> + * @dsize:             data payload size
> >> >> + * @pdata:             message data payload
> >> >> + */
> >> >> +struct sti_mbox_msg {
> >> >> +       u32             dsize;
> >> >> +       u8              *pdata;
> >> >> +};
> >> >
> >> > As mentioned in another thread, we may just want to add a 'size'
> >> > argument to the message send function, and a default helper for
> >> > messages with size of 32 bits.
> >> >
> >> Case-a) 'size' is a member of the payload structure itself
> >>     The extra 'size' argument would only be used for sanity check.
> >>     This driver seems so. Lee, can you not do without 'dsize'?
> >>
> >> Case-b) 'size' is not a member of payload structure:
> >>      b1)  payload is fixed length, that is 'size' := sizeof(struct my_payload)
> >>             Here the size argument is redundant.
> >>
> >>      b2)  payload length varies
> >>             This case is highly unlikely because there would be no way
> >> for remote to know how many bytes to read as the payload. Not to mean
> >> we can't do without the 'size' argument.
> >>
> >> Your opinion has huge weight, but I would like to be enlightened
> >> before agreeing.
> >
> > Let's simplify this.
> >
> > If you want to have varying length payloads, you have to carry the
> > size in the payload.  If you wish to force fixed size payloads, then
> > you may do without a size segment.
> >
> > Do you really want to force all users of Mailbox to use fixed size
> > payloads?
> >
> No. I only observed the fact that every known mailbox controller
> driver already has a way to figure out the payload length because
> either the protocol uses fixed length payloads or has the 'size' field
> in every payload.
> I am yet to see a platform that uses both, then the 'size' argument
> will be helpful but still not necessary.

I see.  So your real concern is that controllers shouldn't have two
means of obtaining size.  Restricting messages to be fixed size sounds
very, well, restrictive.  So we either need to represent the size as
part of the payload or insist on a message-end delimiter.

Arnd's idea of placing the message size as part of the send_message()
call is fine, but it's still going to end up in the payload isn't it?
Or else the recipient isn't going to know the length.  And what about
receiving?  Again, it'll need to be contained, or we won't know how
big the message the co-proc is trying to send.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org ? Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Jassi Brar]

On Wed, Mar 18, 2015 at 8:56 PM, Lee Jones <lee.jones@linaro.org> wrote:
> On Wed, 18 Mar 2015, Jassi Brar wrote:

>> >> > +                       mbox->irq = irq_create_mapping(mbinst->irq_domain,
>> >> > +                                                      mbox->rx_id);
>> >> >
>> >> simply assigning same IRQ to all controller DT nodes and using
>> >> IRQF_SHARED for the common handler, wouldn't work?
>> >
>> > I do have intentions to simplify this driver somewhat, but that will
>> > take some time as it will require a great deal of consultation and
>> > testing from the ST side.  This is the current internal implementation
>> > which is used in the wild and has been fully tested.  If you'll allow
>> > me to conduct my adaptions subsequently we can have full history and a
>> > possible reversion plan if anything untoward take place i.e. I mess
>> > something up.
>> >
>> OK, but wouldn't that break the bindings of this driver when you
>> eventually do that?
>
> That's going to happen regardless, since these bindings are already in
> use internally.  Mainline (i.e. v4.0+) isn't going to be used in
> products for years to come, so we have a lot of time until any new
> bindings become ABI.
>
I thought time starts from upstream. It doesn't seem right to
knowingly introduce a binding that we are going to break in coming
weeks. For this reason, it needs ACK from some DT maintainer.


>> >> > + * struct sti_mbox_msg - sti mailbox message description
>> >> > + * @dsize:             data payload size
>> >> > + * @pdata:             message data payload
>> >> > + */
>> >> > +struct sti_mbox_msg {
>> >> > +       u32             dsize;
>> >> > +       u8              *pdata;
>> >> > +};
>> >> >
>> >> There isn't any client driver in this patchset to tell exactly, but it
>> >> seems the header could be split into one shared between mailbox
>> >> clients and provider and another internal to client/provider ?
>> >
>> > I believe only the above will be required by the client.  Seems silly
>> > to create a client specific header just for that, don't you think?
>> >
>> Do you mean to have copies of the structure in controller and client driver? :O
>
> I do not.  I planned on sharing the main header with with client
> also.
>
> But I guess by your reaction you suggest having a teeny client header
> as the best way forward then.
>
Yes, please. And also no header that's included by exactly one file.

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Jassi Brar]

On Wed, Mar 18, 2015 at 9:04 PM, Lee Jones <lee.jones@linaro.org> wrote:
> On Wed, 18 Mar 2015, Jassi Brar wrote:
>
>> On Wed, Mar 18, 2015 at 6:47 PM, Lee Jones <lee.jones@linaro.org> wrote:
>> > On Tue, 03 Mar 2015, Jassi Brar wrote:
>> >
>> >> On 3 March 2015 at 17:04, Arnd Bergmann <arnd@arndb.de> wrote:
>> >> > On Tuesday 03 March 2015 10:41:23 Lee Jones wrote:
>> >> >> +
>> >> >> +/*
>> >> >> + * struct sti_mbox_msg - sti mailbox message description
>> >> >> + * @dsize:             data payload size
>> >> >> + * @pdata:             message data payload
>> >> >> + */
>> >> >> +struct sti_mbox_msg {
>> >> >> +       u32             dsize;
>> >> >> +       u8              *pdata;
>> >> >> +};
>> >> >
>> >> > As mentioned in another thread, we may just want to add a 'size'
>> >> > argument to the message send function, and a default helper for
>> >> > messages with size of 32 bits.
>> >> >
>> >> Case-a) 'size' is a member of the payload structure itself
>> >>     The extra 'size' argument would only be used for sanity check.
>> >>     This driver seems so. Lee, can you not do without 'dsize'?
>> >>
>> >> Case-b) 'size' is not a member of payload structure:
>> >>      b1)  payload is fixed length, that is 'size' := sizeof(struct my_payload)
>> >>             Here the size argument is redundant.
>> >>
>> >>      b2)  payload length varies
>> >>             This case is highly unlikely because there would be no way
>> >> for remote to know how many bytes to read as the payload. Not to mean
>> >> we can't do without the 'size' argument.
>> >>
>> >> Your opinion has huge weight, but I would like to be enlightened
>> >> before agreeing.
>> >
>> > Let's simplify this.
>> >
>> > If you want to have varying length payloads, you have to carry the
>> > size in the payload.  If you wish to force fixed size payloads, then
>> > you may do without a size segment.
>> >
>> > Do you really want to force all users of Mailbox to use fixed size
>> > payloads?
>> >
>> No. I only observed the fact that every known mailbox controller
>> driver already has a way to figure out the payload length because
>> either the protocol uses fixed length payloads or has the 'size' field
>> in every payload.
>> I am yet to see a platform that uses both, then the 'size' argument
>> will be helpful but still not necessary.
>
> I see.  So your real concern is that controllers shouldn't have two
> means of obtaining size.
>
I think right now there's not much need to expand the api for 'u32'
sized payloads.

> Arnd's idea of placing the message size as part of the send_message()
> call is fine, but it's still going to end up in the payload isn't it?
>
... or it will be implied by sizeof(struct my_packet) if the protocol
has finite set of payloads.

> And what about receiving?
>
Similar to sending - controller driver passes pointer to RX buffer
which the client parses. Remember the protocol would already have a
way to communicate payload length.

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Lee Jones]

On Thu, 19 Mar 2015, Jassi Brar wrote:

> On Wed, Mar 18, 2015 at 9:04 PM, Lee Jones <lee.jones@linaro.org> wrote:
> > On Wed, 18 Mar 2015, Jassi Brar wrote:
> >
> >> On Wed, Mar 18, 2015 at 6:47 PM, Lee Jones <lee.jones@linaro.org> wrote:
> >> > On Tue, 03 Mar 2015, Jassi Brar wrote:
> >> >
> >> >> On 3 March 2015 at 17:04, Arnd Bergmann <arnd@arndb.de> wrote:
> >> >> > On Tuesday 03 March 2015 10:41:23 Lee Jones wrote:
> >> >> >> +
> >> >> >> +/*
> >> >> >> + * struct sti_mbox_msg - sti mailbox message description
> >> >> >> + * @dsize:             data payload size
> >> >> >> + * @pdata:             message data payload
> >> >> >> + */
> >> >> >> +struct sti_mbox_msg {
> >> >> >> +       u32             dsize;
> >> >> >> +       u8              *pdata;
> >> >> >> +};
> >> >> >
> >> >> > As mentioned in another thread, we may just want to add a 'size'
> >> >> > argument to the message send function, and a default helper for
> >> >> > messages with size of 32 bits.
> >> >> >
> >> >> Case-a) 'size' is a member of the payload structure itself
> >> >>     The extra 'size' argument would only be used for sanity check.
> >> >>     This driver seems so. Lee, can you not do without 'dsize'?
> >> >>
> >> >> Case-b) 'size' is not a member of payload structure:
> >> >>      b1)  payload is fixed length, that is 'size' := sizeof(struct my_payload)
> >> >>             Here the size argument is redundant.
> >> >>
> >> >>      b2)  payload length varies
> >> >>             This case is highly unlikely because there would be no way
> >> >> for remote to know how many bytes to read as the payload. Not to mean
> >> >> we can't do without the 'size' argument.
> >> >>
> >> >> Your opinion has huge weight, but I would like to be enlightened
> >> >> before agreeing.
> >> >
> >> > Let's simplify this.
> >> >
> >> > If you want to have varying length payloads, you have to carry the
> >> > size in the payload.  If you wish to force fixed size payloads, then
> >> > you may do without a size segment.
> >> >
> >> > Do you really want to force all users of Mailbox to use fixed size
> >> > payloads?
> >> >
> >> No. I only observed the fact that every known mailbox controller
> >> driver already has a way to figure out the payload length because
> >> either the protocol uses fixed length payloads or has the 'size' field
> >> in every payload.
> >> I am yet to see a platform that uses both, then the 'size' argument
> >> will be helpful but still not necessary.
> >
> > I see.  So your real concern is that controllers shouldn't have two
> > means of obtaining size.
> >
> I think right now there's not much need to expand the api for 'u32'
> sized payloads.
> 
> > Arnd's idea of placing the message size as part of the send_message()
> > call is fine, but it's still going to end up in the payload isn't it?
> >
> ... or it will be implied by sizeof(struct my_packet) if the protocol
> has finite set of payloads.
> 
> > And what about receiving?
> >
> Similar to sending - controller driver passes pointer to RX buffer
> which the client parses. Remember the protocol would already have a
> way to communicate payload length.

So this is the bit that's getting me.  How do you pass payload length
to the remote processor if you don't have it in the payload?  Unless
we are using cross-terminology of course.  I'm thinking that the
payload is the entire message sent to the remote proc i.e:
[[ size ][ data]].

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org ? Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Lee Jones]

On Thu, 19 Mar 2015, Jassi Brar wrote:

> On Wed, Mar 18, 2015 at 8:56 PM, Lee Jones <lee.jones@linaro.org> wrote:
> > On Wed, 18 Mar 2015, Jassi Brar wrote:
> 
> >> >> > +                       mbox->irq = irq_create_mapping(mbinst->irq_domain,
> >> >> > +                                                      mbox->rx_id);
> >> >> >
> >> >> simply assigning same IRQ to all controller DT nodes and using
> >> >> IRQF_SHARED for the common handler, wouldn't work?
> >> >
> >> > I do have intentions to simplify this driver somewhat, but that will
> >> > take some time as it will require a great deal of consultation and
> >> > testing from the ST side.  This is the current internal implementation
> >> > which is used in the wild and has been fully tested.  If you'll allow
> >> > me to conduct my adaptions subsequently we can have full history and a
> >> > possible reversion plan if anything untoward take place i.e. I mess
> >> > something up.
> >> >
> >> OK, but wouldn't that break the bindings of this driver when you
> >> eventually do that?
> >
> > That's going to happen regardless, since these bindings are already in
> > use internally.  Mainline (i.e. v4.0+) isn't going to be used in
> > products for years to come, so we have a lot of time until any new
> > bindings become ABI.
> >
> I thought time starts from upstream. It doesn't seem right to
> knowingly introduce a binding that we are going to break in coming
> weeks. For this reason, it needs ACK from some DT maintainer.

Time starts from when binding comes out of active development mode and
becomes ABI.  I can issue a statement in the binding document to say
that is in a state of flux if that makes you feel better about it.

Development bindings change all the time.

> >> >> > + * struct sti_mbox_msg - sti mailbox message description
> >> >> > + * @dsize:             data payload size
> >> >> > + * @pdata:             message data payload
> >> >> > + */
> >> >> > +struct sti_mbox_msg {
> >> >> > +       u32             dsize;
> >> >> > +       u8              *pdata;
> >> >> > +};
> >> >> >
> >> >> There isn't any client driver in this patchset to tell exactly, but it
> >> >> seems the header could be split into one shared between mailbox
> >> >> clients and provider and another internal to client/provider ?
> >> >
> >> > I believe only the above will be required by the client.  Seems silly
> >> > to create a client specific header just for that, don't you think?
> >> >
> >> Do you mean to have copies of the structure in controller and client driver? :O
> >
> > I do not.  I planned on sharing the main header with with client
> > also.
> >
> > But I guess by your reaction you suggest having a teeny client header
> > as the best way forward then.
> >
> Yes, please.

Roger red leader.

> And also no header that's included by exactly one file.

So you also want me to drag in all of the controller structs into the
driver?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org ? Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Jassi Brar]

On Thu, Mar 19, 2015 at 2:47 PM, Lee Jones <lee.jones@linaro.org> wrote:
> On Thu, 19 Mar 2015, Jassi Brar wrote:
>
>> On Wed, Mar 18, 2015 at 9:04 PM, Lee Jones <lee.jones@linaro.org> wrote:
>> > On Wed, 18 Mar 2015, Jassi Brar wrote:
>> >
>> >> On Wed, Mar 18, 2015 at 6:47 PM, Lee Jones <lee.jones@linaro.org> wrote:
>> >> > On Tue, 03 Mar 2015, Jassi Brar wrote:
>> >> >
>> >> >> On 3 March 2015 at 17:04, Arnd Bergmann <arnd@arndb.de> wrote:
>> >> >> > On Tuesday 03 March 2015 10:41:23 Lee Jones wrote:
>> >> >> >> +
>> >> >> >> +/*
>> >> >> >> + * struct sti_mbox_msg - sti mailbox message description
>> >> >> >> + * @dsize:             data payload size
>> >> >> >> + * @pdata:             message data payload
>> >> >> >> + */
>> >> >> >> +struct sti_mbox_msg {
>> >> >> >> +       u32             dsize;
>> >> >> >> +       u8              *pdata;
>> >> >> >> +};
>> >> >> >
>> >> >> > As mentioned in another thread, we may just want to add a 'size'
>> >> >> > argument to the message send function, and a default helper for
>> >> >> > messages with size of 32 bits.
>> >> >> >
>> >> >> Case-a) 'size' is a member of the payload structure itself
>> >> >>     The extra 'size' argument would only be used for sanity check.
>> >> >>     This driver seems so. Lee, can you not do without 'dsize'?
>> >> >>
>> >> >> Case-b) 'size' is not a member of payload structure:
>> >> >>      b1)  payload is fixed length, that is 'size' := sizeof(struct my_payload)
>> >> >>             Here the size argument is redundant.
>> >> >>
>> >> >>      b2)  payload length varies
>> >> >>             This case is highly unlikely because there would be no way
>> >> >> for remote to know how many bytes to read as the payload. Not to mean
>> >> >> we can't do without the 'size' argument.
>> >> >>
>> >> >> Your opinion has huge weight, but I would like to be enlightened
>> >> >> before agreeing.
>> >> >
>> >> > Let's simplify this.
>> >> >
>> >> > If you want to have varying length payloads, you have to carry the
>> >> > size in the payload.  If you wish to force fixed size payloads, then
>> >> > you may do without a size segment.
>> >> >
>> >> > Do you really want to force all users of Mailbox to use fixed size
>> >> > payloads?
>> >> >
>> >> No. I only observed the fact that every known mailbox controller
>> >> driver already has a way to figure out the payload length because
>> >> either the protocol uses fixed length payloads or has the 'size' field
>> >> in every payload.
>> >> I am yet to see a platform that uses both, then the 'size' argument
>> >> will be helpful but still not necessary.
>> >
>> > I see.  So your real concern is that controllers shouldn't have two
>> > means of obtaining size.
>> >
>> I think right now there's not much need to expand the api for 'u32'
>> sized payloads.
>>
>> > Arnd's idea of placing the message size as part of the send_message()
>> > call is fine, but it's still going to end up in the payload isn't it?
>> >
>> ... or it will be implied by sizeof(struct my_packet) if the protocol
>> has finite set of payloads.
>>
>> > And what about receiving?
>> >
>> Similar to sending - controller driver passes pointer to RX buffer
>> which the client parses. Remember the protocol would already have a
>> way to communicate payload length.
>
> So this is the bit that's getting me.  How do you pass payload length
> to the remote processor if you don't have it in the payload?
>
Some protocol may use signature to identify a packet type.
For example, the remote supports upto 100 commands, each having unique
8bit code. At fixed offset of any payload is the command code. All the
remote needs to do is read the u8 value of predefined offset and use
it dispatch the payload to handler of that command. The command
handler would know the format of such requests.

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Jassi Brar]

On Thu, Mar 19, 2015 at 3:27 PM, Lee Jones <lee.jones@linaro.org> wrote:
> On Thu, 19 Mar 2015, Jassi Brar wrote:
>
>> And also no header that's included by exactly one file.
>
> So you also want me to drag in all of the controller structs into the
> driver?
>
Yes, please. Why have structures, internal to a code, in a header
file? Lets keep file count low.

thanks.

[PATCH 3/3] mailbox: Add support for ST's Mailbox IP

[Lee Jones]

On Thu, 19 Mar 2015, Jassi Brar wrote:

> On Thu, Mar 19, 2015 at 2:47 PM, Lee Jones <lee.jones@linaro.org> wrote:
> > On Thu, 19 Mar 2015, Jassi Brar wrote:
> >
> >> On Wed, Mar 18, 2015 at 9:04 PM, Lee Jones <lee.jones@linaro.org> wrote:
> >> > On Wed, 18 Mar 2015, Jassi Brar wrote:
> >> >
> >> >> On Wed, Mar 18, 2015 at 6:47 PM, Lee Jones <lee.jones@linaro.org> wrote:
> >> >> > On Tue, 03 Mar 2015, Jassi Brar wrote:
> >> >> >
> >> >> >> On 3 March 2015 at 17:04, Arnd Bergmann <arnd@arndb.de> wrote:
> >> >> >> > On Tuesday 03 March 2015 10:41:23 Lee Jones wrote:
> >> >> >> >> +
> >> >> >> >> +/*
> >> >> >> >> + * struct sti_mbox_msg - sti mailbox message description
> >> >> >> >> + * @dsize:             data payload size
> >> >> >> >> + * @pdata:             message data payload
> >> >> >> >> + */
> >> >> >> >> +struct sti_mbox_msg {
> >> >> >> >> +       u32             dsize;
> >> >> >> >> +       u8              *pdata;
> >> >> >> >> +};
> >> >> >> >
> >> >> >> > As mentioned in another thread, we may just want to add a 'size'
> >> >> >> > argument to the message send function, and a default helper for
> >> >> >> > messages with size of 32 bits.
> >> >> >> >
> >> >> >> Case-a) 'size' is a member of the payload structure itself
> >> >> >>     The extra 'size' argument would only be used for sanity check.
> >> >> >>     This driver seems so. Lee, can you not do without 'dsize'?
> >> >> >>
> >> >> >> Case-b) 'size' is not a member of payload structure:
> >> >> >>      b1)  payload is fixed length, that is 'size' := sizeof(struct my_payload)
> >> >> >>             Here the size argument is redundant.
> >> >> >>
> >> >> >>      b2)  payload length varies
> >> >> >>             This case is highly unlikely because there would be no way
> >> >> >> for remote to know how many bytes to read as the payload. Not to mean
> >> >> >> we can't do without the 'size' argument.
> >> >> >>
> >> >> >> Your opinion has huge weight, but I would like to be enlightened
> >> >> >> before agreeing.
> >> >> >
> >> >> > Let's simplify this.
> >> >> >
> >> >> > If you want to have varying length payloads, you have to carry the
> >> >> > size in the payload.  If you wish to force fixed size payloads, then
> >> >> > you may do without a size segment.
> >> >> >
> >> >> > Do you really want to force all users of Mailbox to use fixed size
> >> >> > payloads?
> >> >> >
> >> >> No. I only observed the fact that every known mailbox controller
> >> >> driver already has a way to figure out the payload length because
> >> >> either the protocol uses fixed length payloads or has the 'size' field
> >> >> in every payload.
> >> >> I am yet to see a platform that uses both, then the 'size' argument
> >> >> will be helpful but still not necessary.
> >> >
> >> > I see.  So your real concern is that controllers shouldn't have two
> >> > means of obtaining size.
> >> >
> >> I think right now there's not much need to expand the api for 'u32'
> >> sized payloads.
> >>
> >> > Arnd's idea of placing the message size as part of the send_message()
> >> > call is fine, but it's still going to end up in the payload isn't it?
> >> >
> >> ... or it will be implied by sizeof(struct my_packet) if the protocol
> >> has finite set of payloads.
> >>
> >> > And what about receiving?
> >> >
> >> Similar to sending - controller driver passes pointer to RX buffer
> >> which the client parses. Remember the protocol would already have a
> >> way to communicate payload length.
> >
> > So this is the bit that's getting me.  How do you pass payload length
> > to the remote processor if you don't have it in the payload?
> >
> Some protocol may use signature to identify a packet type.
> For example, the remote supports upto 100 commands, each having unique
> 8bit code. At fixed offset of any payload is the command code. All the
> remote needs to do is read the u8 value of predefined offset and use
> it dispatch the payload to handler of that command. The command
> handler would know the format of such requests.

Okay, I see what you're saying.  We'll push the knowledge of 'command
type', 'size' and anything else we wish to encode into the message
back into the client so the controller doesn't have to worry about
it.  Sounds reasonable to me.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org ? Open source software for ARM SoCs
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