MediaTek MT8173 CMDQ support

MediaTek MT8173 CMDQ support

[Houlong Wei]

Hi,

This is Mediatek MT8173 Command Queue(CMDQ) driver. The CMDQ is used
to help write registers with critical time limitation, such as
updating display configuration during the vblank. It controls Global
Command Engine (GCE) hardware to achieve this requirement.

Changes since v24:
 -move WARN_ON() into cmdq_pkt_append_command() from outside
Changes since v23:
 -rebase on v4.19-rc1
 -revise return value of cmdq_mbox_create()
 -revise cmdq_pkt_create()
 -add MODULE_LICENSE() for mtk-cmdq-helper.c
 -adjust functions order in mtk-cmdq.h
Changes since v22:
 -remove properties 'timeout' and 'thread-num' from device tree
 -move timer from CMDQ driver to CMDQ helper
 -move dma unmap from CMDQ driver to CMDQ helper
 -config thread number in CMDQ match table
 -remove reallocate mechanism and let client specify the cmdq buffer size
 -let client specify the timeout time
Changes since v21:
 -rebase on v4.18-rc1
 -remove subsys code and event id definition from mtk-cmdq-helper.c
 -add mt8173-gce.h to define the subsys code and envent id
Changes since v20:
 -rebase on v4.15-rc1
 -move dma_map_single outside of spinlock
Changes since v19:
 -rebase to v4.10-rc2

Houlong Wei (2):
  arm64: dts: mt8173: Add GCE node
  soc: mediatek: Add Mediatek CMDQ helper

 arch/arm64/boot/dts/mediatek/mt8173.dtsi |   10 +
 drivers/soc/mediatek/Kconfig             |   12 ++
 drivers/soc/mediatek/Makefile            |    1 +
 drivers/soc/mediatek/mtk-cmdq-helper.c   |  291 ++++++++++++++++++++++++++++++
 include/linux/soc/mediatek/mtk-cmdq.h    |  133 ++++++++++++++
 5 files changed, 447 insertions(+)
 create mode 100644 drivers/soc/mediatek/mtk-cmdq-helper.c
 create mode 100644 include/linux/soc/mediatek/mtk-cmdq.h

-- 
1.7.9.5

[PATCH v25 1/2] arm64: dts: mt8173: Add GCE node

[Houlong Wei]

This patch adds the device node of the GCE hardware for CMDQ module.

Signed-off-by: Houlong Wei <houlong.wei@mediatek.com>
Signed-off-by: HS Liao <hs.liao@mediatek.com>
---
 arch/arm64/boot/dts/mediatek/mt8173.dtsi |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/boot/dts/mediatek/mt8173.dtsi b/arch/arm64/boot/dts/mediatek/mt8173.dtsi
index abd2f15..412ffd4 100644
--- a/arch/arm64/boot/dts/mediatek/mt8173.dtsi
+++ b/arch/arm64/boot/dts/mediatek/mt8173.dtsi
@@ -18,6 +18,7 @@
 #include <dt-bindings/phy/phy.h>
 #include <dt-bindings/power/mt8173-power.h>
 #include <dt-bindings/reset/mt8173-resets.h>
+#include <dt-bindings/gce/mt8173-gce.h>
 #include "mt8173-pinfunc.h"
 
 / {
@@ -521,6 +522,15 @@
 			status = "disabled";
 		};
 
+		gce: mailbox@10212000 {
+			compatible = "mediatek,mt8173-gce";
+			reg = <0 0x10212000 0 0x1000>;
+			interrupts = <GIC_SPI 135 IRQ_TYPE_LEVEL_LOW>;
+			clocks = <&infracfg CLK_INFRA_GCE>;
+			clock-names = "gce";
+			#mbox-cells = <3>;
+		};
+
 		mipi_tx0: mipi-dphy@10215000 {
 			compatible = "mediatek,mt8173-mipi-tx";
 			reg = <0 0x10215000 0 0x1000>;
-- 
1.7.9.5

[PATCH v25 2/2] soc: mediatek: Add Mediatek CMDQ helper

[Houlong Wei]

Add Mediatek CMDQ helper to create CMDQ packet and assemble GCE op code.

Signed-off-by: Houlong Wei <houlong.wei@mediatek.com>
Signed-off-by: HS Liao <hs.liao@mediatek.com>
---
 drivers/soc/mediatek/Kconfig           |   12 ++
 drivers/soc/mediatek/Makefile          |    1 +
 drivers/soc/mediatek/mtk-cmdq-helper.c |  291 ++++++++++++++++++++++++++++++++
 include/linux/soc/mediatek/mtk-cmdq.h  |  133 +++++++++++++++
 4 files changed, 437 insertions(+)
 create mode 100644 drivers/soc/mediatek/mtk-cmdq-helper.c
 create mode 100644 include/linux/soc/mediatek/mtk-cmdq.h

diff --git a/drivers/soc/mediatek/Kconfig b/drivers/soc/mediatek/Kconfig
index a7d0667..17bd759 100644
--- a/drivers/soc/mediatek/Kconfig
+++ b/drivers/soc/mediatek/Kconfig
@@ -4,6 +4,18 @@
 menu "MediaTek SoC drivers"
 	depends on ARCH_MEDIATEK || COMPILE_TEST
 
+config MTK_CMDQ
+	tristate "MediaTek CMDQ Support"
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+	select MAILBOX
+	select MTK_CMDQ_MBOX
+	select MTK_INFRACFG
+	help
+	  Say yes here to add support for the MediaTek Command Queue (CMDQ)
+	  driver. The CMDQ is used to help read/write registers with critical
+	  time limitation, such as updating display configuration during the
+	  vblank.
+
 config MTK_INFRACFG
 	bool "MediaTek INFRACFG Support"
 	select REGMAP
diff --git a/drivers/soc/mediatek/Makefile b/drivers/soc/mediatek/Makefile
index 12998b0..64ce5ee 100644
--- a/drivers/soc/mediatek/Makefile
+++ b/drivers/soc/mediatek/Makefile
@@ -1,3 +1,4 @@
+obj-$(CONFIG_MTK_CMDQ) += mtk-cmdq-helper.o
 obj-$(CONFIG_MTK_INFRACFG) += mtk-infracfg.o
 obj-$(CONFIG_MTK_PMIC_WRAP) += mtk-pmic-wrap.o
 obj-$(CONFIG_MTK_SCPSYS) += mtk-scpsys.o
diff --git a/drivers/soc/mediatek/mtk-cmdq-helper.c b/drivers/soc/mediatek/mtk-cmdq-helper.c
new file mode 100644
index 0000000..86a7ab5
--- /dev/null
+++ b/drivers/soc/mediatek/mtk-cmdq-helper.c
@@ -0,0 +1,291 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Copyright (c) 2018 MediaTek Inc.
+
+#include <linux/completion.h>
+#include <linux/errno.h>
+#include <linux/dma-mapping.h>
+#include <linux/module.h>
+#include <linux/mailbox_controller.h>
+#include <linux/soc/mediatek/mtk-cmdq.h>
+
+#define CMDQ_ARG_A_WRITE_MASK	0xffff
+#define CMDQ_WRITE_ENABLE_MASK	BIT(0)
+#define CMDQ_EOC_IRQ_EN		BIT(0)
+#define CMDQ_EOC_CMD		((u64)((CMDQ_CODE_EOC << CMDQ_OP_CODE_SHIFT)) \
+				<< 32 | CMDQ_EOC_IRQ_EN)
+
+static void cmdq_client_timeout(struct timer_list *t)
+{
+	struct cmdq_client *client = from_timer(client, t, timer);
+
+	dev_err(client->client.dev, "cmdq timeout!\n");
+}
+
+struct cmdq_client *cmdq_mbox_create(struct device *dev, int index, u32 timeout)
+{
+	struct cmdq_client *client;
+
+	client = kzalloc(sizeof(*client), GFP_KERNEL);
+	if (!client)
+		return (struct cmdq_client *)-ENOMEM;
+
+	client->timeout_ms = timeout;
+	if (timeout != CMDQ_NO_TIMEOUT) {
+		spin_lock_init(&client->lock);
+		timer_setup(&client->timer, cmdq_client_timeout, 0);
+	}
+	client->pkt_cnt = 0;
+	client->client.dev = dev;
+	client->client.tx_block = false;
+	client->chan = mbox_request_channel(&client->client, index);
+
+	if (IS_ERR(client->chan)) {
+		long err;
+
+		dev_err(dev, "failed to request channel\n");
+		err = PTR_ERR(client->chan);
+		kfree(client);
+
+		return ERR_PTR(err);
+	}
+
+	return client;
+}
+EXPORT_SYMBOL(cmdq_mbox_create);
+
+void cmdq_mbox_destroy(struct cmdq_client *client)
+{
+	if (client->timeout_ms != CMDQ_NO_TIMEOUT) {
+		spin_lock(&client->lock);
+		del_timer_sync(&client->timer);
+		spin_unlock(&client->lock);
+	}
+	mbox_free_channel(client->chan);
+	kfree(client);
+}
+EXPORT_SYMBOL(cmdq_mbox_destroy);
+
+struct cmdq_pkt *cmdq_pkt_create(struct cmdq_client *client, size_t size)
+{
+	struct cmdq_pkt *pkt;
+	struct device *dev;
+	dma_addr_t dma_addr;
+
+	pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
+	if (!pkt)
+		return ERR_PTR(-ENOMEM);
+	pkt->va_base = kzalloc(size, GFP_KERNEL);
+	if (!pkt->va_base) {
+		kfree(pkt);
+		return ERR_PTR(-ENOMEM);
+	}
+	pkt->buf_size = size;
+	pkt->cl = (void *)client;
+
+	dev = client->chan->mbox->dev;
+	dma_addr = dma_map_single(dev, pkt->va_base, pkt->buf_size,
+				  DMA_TO_DEVICE);
+	if (dma_mapping_error(dev, dma_addr)) {
+		dev_err(dev, "dma map failed, size=%u\n", (u32)(u64)size);
+		kfree(pkt->va_base);
+		kfree(pkt);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	pkt->pa_base = dma_addr;
+
+	return pkt;
+}
+EXPORT_SYMBOL(cmdq_pkt_create);
+
+void cmdq_pkt_destroy(struct cmdq_pkt *pkt)
+{
+	struct cmdq_client *client = (struct cmdq_client *)pkt->cl;
+
+	dma_unmap_single(client->chan->mbox->dev, pkt->pa_base, pkt->buf_size,
+			 DMA_TO_DEVICE);
+	kfree(pkt->va_base);
+	kfree(pkt);
+}
+EXPORT_SYMBOL(cmdq_pkt_destroy);
+
+static int cmdq_pkt_append_command(struct cmdq_pkt *pkt, enum cmdq_code code,
+				   u32 arg_a, u32 arg_b)
+{
+	u64 *cmd_ptr;
+
+	if (unlikely(pkt->cmd_buf_size + CMDQ_INST_SIZE > pkt->buf_size)) {
+		pkt->cmd_buf_size += CMDQ_INST_SIZE;
+		WARN_ON(1);
+		return -ENOMEM;
+	}
+	cmd_ptr = pkt->va_base + pkt->cmd_buf_size;
+	(*cmd_ptr) = (u64)((code << CMDQ_OP_CODE_SHIFT) | arg_a) << 32 | arg_b;
+	pkt->cmd_buf_size += CMDQ_INST_SIZE;
+
+	return 0;
+}
+
+int cmdq_pkt_write(struct cmdq_pkt *pkt, u32 value, u32 subsys, u32 offset)
+{
+	u32 arg_a = (offset & CMDQ_ARG_A_WRITE_MASK) |
+		    (subsys << CMDQ_SUBSYS_SHIFT);
+
+	return cmdq_pkt_append_command(pkt, CMDQ_CODE_WRITE, arg_a, value);
+}
+EXPORT_SYMBOL(cmdq_pkt_write);
+
+int cmdq_pkt_write_mask(struct cmdq_pkt *pkt, u32 value,
+			u32 subsys, u32 offset, u32 mask)
+{
+	u32 offset_mask = offset;
+	int err = 0;
+
+	if (mask != 0xffffffff) {
+		err = cmdq_pkt_append_command(pkt, CMDQ_CODE_MASK, 0, ~mask);
+		offset_mask |= CMDQ_WRITE_ENABLE_MASK;
+	}
+	err |= cmdq_pkt_write(pkt, value, subsys, offset_mask);
+
+	return err;
+}
+EXPORT_SYMBOL(cmdq_pkt_write_mask);
+
+int cmdq_pkt_wfe(struct cmdq_pkt *pkt, u32 event)
+{
+	u32 arg_b;
+
+	if (event >= CMDQ_MAX_EVENT)
+		return -EINVAL;
+
+	/*
+	 * WFE arg_b
+	 * bit 0-11: wait value
+	 * bit 15: 1 - wait, 0 - no wait
+	 * bit 16-27: update value
+	 * bit 31: 1 - update, 0 - no update
+	 */
+	arg_b = CMDQ_WFE_UPDATE | CMDQ_WFE_WAIT | CMDQ_WFE_WAIT_VALUE;
+
+	return cmdq_pkt_append_command(pkt, CMDQ_CODE_WFE, event, arg_b);
+}
+EXPORT_SYMBOL(cmdq_pkt_wfe);
+
+int cmdq_pkt_clear_event(struct cmdq_pkt *pkt, u32 event)
+{
+	if (event >= CMDQ_MAX_EVENT)
+		return -EINVAL;
+
+	return cmdq_pkt_append_command(pkt, CMDQ_CODE_WFE, event,
+				       CMDQ_WFE_UPDATE);
+}
+EXPORT_SYMBOL(cmdq_pkt_clear_event);
+
+static int cmdq_pkt_finalize(struct cmdq_pkt *pkt)
+{
+	int err;
+
+	/* insert EOC and generate IRQ for each command iteration */
+	err = cmdq_pkt_append_command(pkt, CMDQ_CODE_EOC, 0, CMDQ_EOC_IRQ_EN);
+
+	/* JUMP to end */
+	err |= cmdq_pkt_append_command(pkt, CMDQ_CODE_JUMP, 0, CMDQ_JUMP_PASS);
+
+	return err;
+}
+
+static void cmdq_pkt_flush_async_cb(struct cmdq_cb_data data)
+{
+	struct cmdq_pkt *pkt = (struct cmdq_pkt *)data.data;
+	struct cmdq_task_cb *cb = &pkt->cb;
+	struct cmdq_client *client = (struct cmdq_client *)pkt->cl;
+
+	if (client->timeout_ms != CMDQ_NO_TIMEOUT) {
+		unsigned long flags = 0;
+
+		spin_lock_irqsave(&client->lock, flags);
+		if (--client->pkt_cnt == 0)
+			del_timer(&client->timer);
+		else
+			mod_timer(&client->timer, jiffies +
+				  msecs_to_jiffies(client->timeout_ms));
+		spin_unlock_irqrestore(&client->lock, flags);
+	}
+
+	dma_sync_single_for_cpu(client->chan->mbox->dev, pkt->pa_base,
+				pkt->cmd_buf_size, DMA_TO_DEVICE);
+	if (cb->cb) {
+		data.data = cb->data;
+		cb->cb(data);
+	}
+}
+
+int cmdq_pkt_flush_async(struct cmdq_pkt *pkt, cmdq_async_flush_cb cb,
+			 void *data)
+{
+	int err;
+	unsigned long flags = 0;
+	struct cmdq_client *client = (struct cmdq_client *)pkt->cl;
+
+	err = cmdq_pkt_finalize(pkt);
+	if (err < 0)
+		return err;
+
+	pkt->cb.cb = cb;
+	pkt->cb.data = data;
+	pkt->async_cb.cb = cmdq_pkt_flush_async_cb;
+	pkt->async_cb.data = pkt;
+
+	dma_sync_single_for_device(client->chan->mbox->dev, pkt->pa_base,
+				   pkt->cmd_buf_size, DMA_TO_DEVICE);
+
+	if (client->timeout_ms != CMDQ_NO_TIMEOUT) {
+		spin_lock_irqsave(&client->lock, flags);
+		if (client->pkt_cnt++ == 0)
+			mod_timer(&client->timer, jiffies +
+				  msecs_to_jiffies(client->timeout_ms));
+		spin_unlock_irqrestore(&client->lock, flags);
+	}
+
+	mbox_send_message(client->chan, pkt);
+	/* We can send next packet immediately, so just call txdone. */
+	mbox_client_txdone(client->chan, 0);
+
+	return 0;
+}
+EXPORT_SYMBOL(cmdq_pkt_flush_async);
+
+struct cmdq_flush_completion {
+	struct completion cmplt;
+	bool err;
+};
+
+static void cmdq_pkt_flush_cb(struct cmdq_cb_data data)
+{
+	struct cmdq_flush_completion *cmplt;
+
+	cmplt = (struct cmdq_flush_completion *)data.data;
+	if (data.sta != CMDQ_CB_NORMAL)
+		cmplt->err = true;
+	else
+		cmplt->err = false;
+	complete(&cmplt->cmplt);
+}
+
+int cmdq_pkt_flush(struct cmdq_pkt *pkt)
+{
+	struct cmdq_flush_completion cmplt;
+	int err;
+
+	init_completion(&cmplt.cmplt);
+	err = cmdq_pkt_flush_async(pkt, cmdq_pkt_flush_cb, &cmplt);
+	if (err < 0)
+		return err;
+	wait_for_completion(&cmplt.cmplt);
+
+	return cmplt.err ? -EFAULT : 0;
+}
+EXPORT_SYMBOL(cmdq_pkt_flush);
+
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/soc/mediatek/mtk-cmdq.h b/include/linux/soc/mediatek/mtk-cmdq.h
new file mode 100644
index 0000000..54ade13
--- /dev/null
+++ b/include/linux/soc/mediatek/mtk-cmdq.h
@@ -0,0 +1,133 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2018 MediaTek Inc.
+ *
+ */
+
+#ifndef __MTK_CMDQ_H__
+#define __MTK_CMDQ_H__
+
+#include <linux/mailbox_client.h>
+#include <linux/mailbox/mtk-cmdq-mailbox.h>
+#include <linux/timer.h>
+
+#define CMDQ_NO_TIMEOUT		0xffffffffu
+
+/** cmdq event maximum */
+#define CMDQ_MAX_EVENT				0x3ff
+
+struct cmdq_pkt;
+
+struct cmdq_client {
+	spinlock_t lock;
+	u32 pkt_cnt;
+	struct mbox_client client;
+	struct mbox_chan *chan;
+	struct timer_list timer;
+	u32 timeout_ms; /* in unit of microsecond */
+};
+
+/**
+ * cmdq_mbox_create() - create CMDQ mailbox client and channel
+ * @dev:	device of CMDQ mailbox client
+ * @index:	index of CMDQ mailbox channel
+ * @timeout:	timeout of a pkt execution by GCE, in unit of microsecond, set
+ *		CMDQ_NO_TIMEOUT if a timer is not used.
+ *
+ * Return: CMDQ mailbox client pointer
+ */
+struct cmdq_client *cmdq_mbox_create(struct device *dev, int index,
+				     u32 timeout);
+
+/**
+ * cmdq_mbox_destroy() - destroy CMDQ mailbox client and channel
+ * @client:	the CMDQ mailbox client
+ */
+void cmdq_mbox_destroy(struct cmdq_client *client);
+
+/**
+ * cmdq_pkt_create() - create a CMDQ packet
+ * @client:	the CMDQ mailbox client
+ * @size:	required CMDQ buffer size
+ *
+ * Return: CMDQ packet pointer
+ */
+struct cmdq_pkt *cmdq_pkt_create(struct cmdq_client *client, size_t size);
+
+/**
+ * cmdq_pkt_destroy() - destroy the CMDQ packet
+ * @pkt:	the CMDQ packet
+ */
+void cmdq_pkt_destroy(struct cmdq_pkt *pkt);
+
+/**
+ * cmdq_pkt_write() - append write command to the CMDQ packet
+ * @pkt:	the CMDQ packet
+ * @value:	the specified target register value
+ * @subsys:	the CMDQ sub system code
+ * @offset:	register offset from CMDQ sub system
+ *
+ * Return: 0 for success; else the error code is returned
+ */
+int cmdq_pkt_write(struct cmdq_pkt *pkt, u32 value, u32 subsys, u32 offset);
+
+/**
+ * cmdq_pkt_write_mask() - append write command with mask to the CMDQ packet
+ * @pkt:	the CMDQ packet
+ * @value:	the specified target register value
+ * @subsys:	the CMDQ sub system code
+ * @offset:	register offset from CMDQ sub system
+ * @mask:	the specified target register mask
+ *
+ * Return: 0 for success; else the error code is returned
+ */
+int cmdq_pkt_write_mask(struct cmdq_pkt *pkt, u32 value,
+			u32 subsys, u32 offset, u32 mask);
+
+/**
+ * cmdq_pkt_wfe() - append wait for event command to the CMDQ packet
+ * @pkt:	the CMDQ packet
+ * @event:	the desired event type to "wait and CLEAR"
+ *
+ * Return: 0 for success; else the error code is returned
+ */
+int cmdq_pkt_wfe(struct cmdq_pkt *pkt, u32 event);
+
+/**
+ * cmdq_pkt_clear_event() - append clear event command to the CMDQ packet
+ * @pkt:	the CMDQ packet
+ * @event:	the desired event to be cleared
+ *
+ * Return: 0 for success; else the error code is returned
+ */
+int cmdq_pkt_clear_event(struct cmdq_pkt *pkt, u32 event);
+
+/**
+ * cmdq_pkt_flush_async() - trigger CMDQ to asynchronously execute the CMDQ
+ *                          packet and call back at the end of done packet
+ * @pkt:	the CMDQ packet
+ * @cb:		called at the end of done packet
+ * @data:	this data will pass back to cb
+ *
+ * Return: 0 for success; else the error code is returned
+ *
+ * Trigger CMDQ to asynchronously execute the CMDQ packet and call back
+ * at the end of done packet. Note that this is an ASYNC function. When the
+ * function returned, it may or may not be finished.
+ */
+int cmdq_pkt_flush_async(struct cmdq_pkt *pkt, cmdq_async_flush_cb cb,
+			 void *data);
+
+/**
+ * cmdq_pkt_flush() - trigger CMDQ to execute the CMDQ packet
+ * @pkt:	the CMDQ packet
+ *
+ * Return: 0 for success; else the error code is returned
+ *
+ * Trigger CMDQ to execute the CMDQ packet. Note that this is a
+ * synchronous flush function. When the function returned, the recorded
+ * commands have been done.
+ */
+int cmdq_pkt_flush(struct cmdq_pkt *pkt);
+
+#endif	/* __MTK_CMDQ_H__ */
-- 
1.7.9.5

Re: [PATCH v25 2/2] soc: mediatek: Add Mediatek CMDQ helper

[Matthias Brugger]

On 29/09/2018 11:21, Houlong Wei wrote:
[...]

> +static int cmdq_pkt_append_command(struct cmdq_pkt *pkt, enum cmdq_code code,
> +				   u32 arg_a, u32 arg_b)
> +{
> +	u64 *cmd_ptr;
> +
> +	if (unlikely(pkt->cmd_buf_size + CMDQ_INST_SIZE > pkt->buf_size)) {
> +		pkt->cmd_buf_size += CMDQ_INST_SIZE;

Can you plesae provide some example code of a driver that will use this API, I
still don't understand why you need to update the cmd_buf_size here.

> +		WARN_ON(1);

can we add some debug information:
WARN_ON(1, "%s: buffer size too small for the amount of commands", __func__);

Would it make sense to use WARN_ONCE()?

> +		return -ENOMEM;
> +	}
> +	cmd_ptr = pkt->va_base + pkt->cmd_buf_size;
> +	(*cmd_ptr) = (u64)((code << CMDQ_OP_CODE_SHIFT) | arg_a) << 32 | arg_b;
> +	pkt->cmd_buf_size += CMDQ_INST_SIZE;
> +
> +	return 0;
> +}

Thanks,
Matthias

Re: [PATCH v25 2/2] soc: mediatek: Add Mediatek CMDQ helper

[houlong wei]

On Sat, 2018-09-29 at 20:50 +0800, Matthias Brugger wrote:
> 
> On 29/09/2018 11:21, Houlong Wei wrote:
> [...]
> 
> > +static int cmdq_pkt_append_command(struct cmdq_pkt *pkt, enum cmdq_code code,
> > +				   u32 arg_a, u32 arg_b)
> > +{
> > +	u64 *cmd_ptr;
> > +
> > +	if (unlikely(pkt->cmd_buf_size + CMDQ_INST_SIZE > pkt->buf_size)) {
> > +		pkt->cmd_buf_size += CMDQ_INST_SIZE;
> 
> Can you plesae provide some example code of a driver that will use this API, I
> still don't understand why you need to update the cmd_buf_size here.

In our previous design, when appending a new command to buffer and the
buffer gets overflow, we will re-allocate a larger buffer to use.
CK.Hu had concern about the performance of buffer re-allocation. Please
refer:
http://lists.infradead.org/pipermail/linux-mediatek/2018-June/013797.html
One of his suggestions is that the consumer dynamically allocates buffer
with a initial size. Because the consumer doesn't know how to calculate
the buffer size. So we increase cmdq_buf_size here, that will help the
consumer get the buffer size in developing phase. In release driver
code, consumer passes a constant value to function call
cmdq_pkt_create(client, cmdq_buffer_size), cmdq_buffer_size is the
specified command queue buffer size.

> 
> > +		WARN_ON(1);
> 
> can we add some debug information:
> WARN_ON(1, "%s: buffer size too small for the amount of commands", __func__);
> 
> Would it make sense to use WARN_ONCE()?
> 
Yes, I will add debug information and use WARN_ONCE().

> > +		return -ENOMEM;
> > +	}
> > +	cmd_ptr = pkt->va_base + pkt->cmd_buf_size;
> > +	(*cmd_ptr) = (u64)((code << CMDQ_OP_CODE_SHIFT) | arg_a) << 32 | arg_b;
> > +	pkt->cmd_buf_size += CMDQ_INST_SIZE;
> > +
> > +	return 0;
> > +}
> 
> Thanks,
> Matthias