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Message-ID: <1519185212.8716.32.camel@mtksdaap41>
Subject: Re: [PATCH v21 2/4] mailbox: mediatek: Add Mediatek CMDQ driver
From:   CK Hu <ck.hu@mediatek.com>
To:     <houlong.wei@mediatek.com>
CC:     Jassi Brar <jassisinghbrar@gmail.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Daniel Kurtz <djkurtz@chromium.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-mediatek@lists.infradead.org>,
        <srv_heupstream@mediatek.com>,
        Sascha Hauer <kernel@pengutronix.de>,
        "Philipp Zabel" <p.zabel@pengutronix.de>,
        Nicolas Boichat <drinkcat@chromium.org>,
        cawa cheng <cawa.cheng@mediatek.com>,
        Bibby Hsieh <bibby.hsieh@mediatek.com>,
        YT Shen <yt.shen@mediatek.com>,
        Daoyuan Huang <daoyuan.huang@mediatek.com>,
        Damon Chu <damon.chu@mediatek.com>,
        "Josh-YC Liu" <josh-yc.liu@mediatek.com>,
        Glory Hung <glory.hung@mediatek.com>,
        Jiaguang Zhang <jiaguang.zhang@mediatek.com>,
        Dennis-YC Hsieh <dennis-yc.hsieh@mediatek.com>,
        Monica Wang <monica.wang@mediatek.com>,
        "HS Liao" <hs.liao@mediatek.com>
Date:   Wed, 21 Feb 2018 11:53:32 +0800
In-Reply-To: <1517383693-25591-3-git-send-email-houlong.wei@mediatek.com>
References: <1517383693-25591-1-git-send-email-houlong.wei@mediatek.com>
         <1517383693-25591-3-git-send-email-houlong.wei@mediatek.com>
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Hi, Houlong:

I've one inline comment.

On Wed, 2018-01-31 at 15:28 +0800, houlong.wei@mediatek.com wrote:
> From: "hs.liao@mediatek.com" <hs.liao@mediatek.com>
> 
> This patch is first version of Mediatek 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.
> Currently, CMDQ only supports display related hardwares, but we expect
> it can be extended to other hardwares for future requirements.
> 
> Signed-off-by: Houlong Wei <houlong.wei@mediatek.com>
> Signed-off-by: HS Liao <hs.liao@mediatek.com>
> Signed-off-by: CK Hu <ck.hu@mediatek.com>
> ---
>  drivers/mailbox/Kconfig                  |   10 +
>  drivers/mailbox/Makefile                 |    2 +
>  drivers/mailbox/mtk-cmdq-mailbox.c       |  594 ++++++++++++++++++++++++++++++
>  include/linux/mailbox/mtk-cmdq-mailbox.h |   77 ++++
>  4 files changed, 683 insertions(+)
>  create mode 100644 drivers/mailbox/mtk-cmdq-mailbox.c
>  create mode 100644 include/linux/mailbox/mtk-cmdq-mailbox.h
> 
> diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
> index ba2f152..43bb26f 100644
> --- a/drivers/mailbox/Kconfig
> +++ b/drivers/mailbox/Kconfig
> @@ -171,4 +171,14 @@ config BCM_FLEXRM_MBOX
>  	  Mailbox implementation of the Broadcom FlexRM ring manager,
>  	  which provides access to various offload engines on Broadcom
>  	  SoCs. Say Y here if you want to use the Broadcom FlexRM.
> +
> +config MTK_CMDQ_MBOX
> +	bool "MediaTek CMDQ Mailbox Support"
> +	depends on ARM64 && ( ARCH_MEDIATEK || COMPILE_TEST )
> +	select MTK_INFRACFG
> +	help
> +	  Say yes here to add support for the MediaTek Command Queue (CMDQ)
> +	  mailbox driver. The CMDQ is used to help read/write registers with
> +	  critical time limitation, such as updating display configuration
> +	  during the vblank.
>  endif
> diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
> index 4896f8d..484d341 100644
> --- a/drivers/mailbox/Makefile
> +++ b/drivers/mailbox/Makefile
> @@ -36,3 +36,5 @@ obj-$(CONFIG_BCM_FLEXRM_MBOX)	+= bcm-flexrm-mailbox.o
>  obj-$(CONFIG_QCOM_APCS_IPC)	+= qcom-apcs-ipc-mailbox.o
>  
>  obj-$(CONFIG_TEGRA_HSP_MBOX)	+= tegra-hsp.o
> +
> +obj-$(CONFIG_MTK_CMDQ_MBOX)	+= mtk-cmdq-mailbox.o
> diff --git a/drivers/mailbox/mtk-cmdq-mailbox.c b/drivers/mailbox/mtk-cmdq-mailbox.c
> new file mode 100644
> index 0000000..394a335
> --- /dev/null
> +++ b/drivers/mailbox/mtk-cmdq-mailbox.c
> @@ -0,0 +1,594 @@
> +/*
> + * Copyright (c) 2015 MediaTek Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/clk.h>
> +#include <linux/clk-provider.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/errno.h>
> +#include <linux/interrupt.h>
> +#include <linux/iopoll.h>
> +#include <linux/kernel.h>
> +#include <linux/mailbox_controller.h>
> +#include <linux/mailbox/mtk-cmdq-mailbox.h>
> +#include <linux/timer.h>
> +
> +#define CMDQ_THR_MAX_COUNT		16
> +#define CMDQ_OP_CODE_MASK		(0xff << CMDQ_OP_CODE_SHIFT)
> +#define CMDQ_TIMEOUT_MS			1000
> +#define CMDQ_IRQ_MASK			0xffff
> +#define CMDQ_NUM_CMD(t)			(t->cmd_buf_size / CMDQ_INST_SIZE)
> +
> +#define CMDQ_CURR_IRQ_STATUS		0x10
> +#define CMDQ_THR_SLOT_CYCLES		0x30
> +
> +#define CMDQ_THR_BASE			0x100
> +#define CMDQ_THR_SIZE			0x80
> +#define CMDQ_THR_WARM_RESET		0x00
> +#define CMDQ_THR_ENABLE_TASK		0x04
> +#define CMDQ_THR_SUSPEND_TASK		0x08
> +#define CMDQ_THR_CURR_STATUS		0x0c
> +#define CMDQ_THR_IRQ_STATUS		0x10
> +#define CMDQ_THR_IRQ_ENABLE		0x14
> +#define CMDQ_THR_CURR_ADDR		0x20
> +#define CMDQ_THR_END_ADDR		0x24
> +#define CMDQ_THR_WAIT_TOKEN		0x30
> +
> +#define CMDQ_THR_ENABLED		0x1
> +#define CMDQ_THR_DISABLED		0x0
> +#define CMDQ_THR_SUSPEND		0x1
> +#define CMDQ_THR_RESUME			0x0
> +#define CMDQ_THR_STATUS_SUSPENDED	BIT(1)
> +#define CMDQ_THR_DO_WARM_RESET		BIT(0)
> +#define CMDQ_THR_ACTIVE_SLOT_CYCLES	0x3200
> +#define CMDQ_THR_IRQ_DONE		0x1
> +#define CMDQ_THR_IRQ_ERROR		0x12
> +#define CMDQ_THR_IRQ_EN			(CMDQ_THR_IRQ_ERROR | CMDQ_THR_IRQ_DONE)
> +#define CMDQ_THR_IS_WAITING		BIT(31)
> +
> +#define CMDQ_JUMP_BY_OFFSET		0x10000000
> +#define CMDQ_JUMP_BY_PA			0x10000001
> +
> +struct cmdq_thread {
> +	struct mbox_chan	*chan;
> +	void __iomem		*base;
> +	struct list_head	task_busy_list;
> +	struct timer_list	timeout;
> +	bool			atomic_exec;
> +};
> +
> +struct cmdq_task {
> +	struct cmdq		*cmdq;
> +	struct list_head	list_entry;
> +	dma_addr_t		pa_base;
> +	struct cmdq_thread	*thread;
> +	struct cmdq_pkt		*pkt; /* the packet sent from mailbox client */
> +};
> +
> +struct cmdq {
> +	struct mbox_controller	mbox;
> +	void __iomem		*base;
> +	u32			irq;
> +	struct cmdq_thread	thread[CMDQ_THR_MAX_COUNT];
> +	struct clk		*clock;
> +	bool			suspended;
> +};
> +
> +static int cmdq_thread_suspend(struct cmdq *cmdq, struct cmdq_thread *thread)
> +{
> +	u32 status;
> +
> +	writel(CMDQ_THR_SUSPEND, thread->base + CMDQ_THR_SUSPEND_TASK);
> +
> +	/* If already disabled, treat as suspended successful. */
> +	if (!(readl(thread->base + CMDQ_THR_ENABLE_TASK) & CMDQ_THR_ENABLED))
> +		return 0;
> +
> +	if (readl_poll_timeout_atomic(thread->base + CMDQ_THR_CURR_STATUS,
> +			status, status & CMDQ_THR_STATUS_SUSPENDED, 0, 10)) {
> +		dev_err(cmdq->mbox.dev, "suspend GCE thread 0x%x failed\n",
> +			(u32)(thread->base - cmdq->base));
> +		return -EFAULT;
> +	}
> +
> +	return 0;
> +}
> +
> +static void cmdq_thread_resume(struct cmdq_thread *thread)
> +{
> +	writel(CMDQ_THR_RESUME, thread->base + CMDQ_THR_SUSPEND_TASK);
> +}
> +
> +static int cmdq_thread_reset(struct cmdq *cmdq, struct cmdq_thread *thread)
> +{
> +	u32 warm_reset;
> +
> +	writel(CMDQ_THR_DO_WARM_RESET, thread->base + CMDQ_THR_WARM_RESET);
> +	if (readl_poll_timeout_atomic(thread->base + CMDQ_THR_WARM_RESET,
> +			warm_reset, !(warm_reset & CMDQ_THR_DO_WARM_RESET),
> +			0, 10)) {
> +		dev_err(cmdq->mbox.dev, "reset GCE thread 0x%x failed\n",
> +			(u32)(thread->base - cmdq->base));
> +		return -EFAULT;
> +	}
> +	writel(CMDQ_THR_ACTIVE_SLOT_CYCLES, cmdq->base + CMDQ_THR_SLOT_CYCLES);
> +	return 0;
> +}
> +
> +static void cmdq_thread_disable(struct cmdq *cmdq, struct cmdq_thread *thread)
> +{
> +	cmdq_thread_reset(cmdq, thread);
> +	writel(CMDQ_THR_DISABLED, thread->base + CMDQ_THR_ENABLE_TASK);
> +}
> +
> +/* notify GCE to re-fetch commands by setting GCE thread PC */
> +static void cmdq_thread_invalidate_fetched_data(struct cmdq_thread *thread)
> +{
> +	writel(readl(thread->base + CMDQ_THR_CURR_ADDR),
> +	       thread->base + CMDQ_THR_CURR_ADDR);
> +}
> +
> +static void cmdq_task_insert_into_thread(struct cmdq_task *task)
> +{
> +	struct device *dev = task->cmdq->mbox.dev;
> +	struct cmdq_thread *thread = task->thread;
> +	struct cmdq_task *prev_task = list_last_entry(
> +			&thread->task_busy_list, typeof(*task), list_entry);
> +	u64 *prev_task_base = prev_task->pkt->va_base;
> +
> +	/* let previous task jump to this task */
> +	dma_sync_single_for_cpu(dev, prev_task->pa_base,
> +				prev_task->pkt->cmd_buf_size, DMA_TO_DEVICE);
> +	prev_task_base[CMDQ_NUM_CMD(prev_task->pkt) - 1] =
> +		(u64)CMDQ_JUMP_BY_PA << 32 | task->pa_base;
> +	dma_sync_single_for_device(dev, prev_task->pa_base,
> +				   prev_task->pkt->cmd_buf_size, DMA_TO_DEVICE);
> +
> +	cmdq_thread_invalidate_fetched_data(thread);
> +}
> +
> +static bool cmdq_command_is_wfe(u64 cmd)
> +{
> +	u64 wfe_option = CMDQ_WFE_UPDATE | CMDQ_WFE_WAIT | CMDQ_WFE_WAIT_VALUE;
> +	u64 wfe_op = (u64)(CMDQ_CODE_WFE << CMDQ_OP_CODE_SHIFT) << 32;
> +	u64 wfe_mask = (u64)CMDQ_OP_CODE_MASK << 32 | 0xffffffff;
> +
> +	return ((cmd & wfe_mask) == (wfe_op | wfe_option));
> +}
> +
> +/* we assume tasks in the same display GCE thread are waiting the same event. */
> +static void cmdq_task_remove_wfe(struct cmdq_task *task)
> +{
> +	struct device *dev = task->cmdq->mbox.dev;
> +	u64 *base = task->pkt->va_base;
> +	int i;
> +
> +	dma_sync_single_for_cpu(dev, task->pa_base, task->pkt->cmd_buf_size,
> +				DMA_TO_DEVICE);
> +	for (i = 0; i < CMDQ_NUM_CMD(task->pkt); i++)
> +		if (cmdq_command_is_wfe(base[i]))
> +			base[i] = (u64)CMDQ_JUMP_BY_OFFSET << 32 |
> +				  CMDQ_JUMP_PASS;
> +	dma_sync_single_for_device(dev, task->pa_base, task->pkt->cmd_buf_size,
> +				   DMA_TO_DEVICE);
> +}
> +
> +static bool cmdq_thread_is_in_wfe(struct cmdq_thread *thread)
> +{
> +	return readl(thread->base + CMDQ_THR_WAIT_TOKEN) & CMDQ_THR_IS_WAITING;
> +}
> +
> +static void cmdq_thread_wait_end(struct cmdq_thread *thread,
> +				 unsigned long end_pa)
> +{
> +	struct device *dev = thread->chan->mbox->dev;
> +	unsigned long curr_pa;
> +
> +	if (readl_poll_timeout_atomic(thread->base + CMDQ_THR_CURR_ADDR,
> +			curr_pa, curr_pa == end_pa, 1, 20))
> +		dev_err(dev, "GCE thread cannot run to end.\n");
> +}
> +
> +static void cmdq_task_exec(struct cmdq_pkt *pkt, struct cmdq_thread *thread)
> +{
> +	struct cmdq *cmdq;
> +	struct cmdq_task *task;
> +	unsigned long curr_pa, end_pa;
> +
> +	cmdq = dev_get_drvdata(thread->chan->mbox->dev);
> +
> +	/* Client should not flush new tasks if suspended. */
> +	WARN_ON(cmdq->suspended);
> +
> +	task = kzalloc(sizeof(*task), GFP_ATOMIC);
> +	task->cmdq = cmdq;
> +	INIT_LIST_HEAD(&task->list_entry);
> +	task->pa_base = pkt->pa_base;
> +	task->thread = thread;
> +	task->pkt = pkt;
> +
> +	if (list_empty(&thread->task_busy_list)) {
> +		WARN_ON(clk_enable(cmdq->clock) < 0);
> +		WARN_ON(cmdq_thread_reset(cmdq, thread) < 0);
> +
> +		writel(task->pa_base, thread->base + CMDQ_THR_CURR_ADDR);
> +		writel(task->pa_base + pkt->cmd_buf_size,
> +		       thread->base + CMDQ_THR_END_ADDR);
> +		writel(CMDQ_THR_IRQ_EN, thread->base + CMDQ_THR_IRQ_ENABLE);
> +		writel(CMDQ_THR_ENABLED, thread->base + CMDQ_THR_ENABLE_TASK);
> +
> +		mod_timer(&thread->timeout,
> +			  jiffies + msecs_to_jiffies(CMDQ_TIMEOUT_MS));
> +	} else {
> +		WARN_ON(cmdq_thread_suspend(cmdq, thread) < 0);
> +		curr_pa = readl(thread->base + CMDQ_THR_CURR_ADDR);
> +		end_pa = readl(thread->base + CMDQ_THR_END_ADDR);
> +
> +		/*
> +		 * Atomic execution should remove the following wfe, i.e. only
> +		 * wait event at first task, and prevent to pause when running.
> +		 */
> +		if (thread->atomic_exec) {
> +			/* GCE is executing if command is not WFE */
> +			if (!cmdq_thread_is_in_wfe(thread)) {
> +				cmdq_thread_resume(thread);
> +				cmdq_thread_wait_end(thread, end_pa);
> +				WARN_ON(cmdq_thread_suspend(cmdq, thread) < 0);
> +				/* set to this task directly */
> +				writel(task->pa_base,
> +				       thread->base + CMDQ_THR_CURR_ADDR);
> +			} else {
> +				cmdq_task_insert_into_thread(task);
> +				cmdq_task_remove_wfe(task);
> +				smp_mb(); /* modify jump before enable thread */
> +			}
> +		} else {
> +			/* check boundary */
> +			if (curr_pa == end_pa - CMDQ_INST_SIZE ||
> +			    curr_pa == end_pa) {
> +				/* set to this task directly */
> +				writel(task->pa_base,
> +				       thread->base + CMDQ_THR_CURR_ADDR);
> +			} else {
> +				cmdq_task_insert_into_thread(task);
> +				smp_mb(); /* modify jump before enable thread */
> +			}
> +		}
> +		writel(task->pa_base + pkt->cmd_buf_size,
> +		       thread->base + CMDQ_THR_END_ADDR);
> +		cmdq_thread_resume(thread);
> +	}
> +	list_move_tail(&task->list_entry, &thread->task_busy_list);

You implement a list to queue command because you need to execute
multiple packet in the same vblank period. I've a suggestion that you
need not to implement a list. Once cmdq driver receive two packet as
below:

Packet 1:
(1) clear vblank event
(2) wait vblank event
(3) write register setting 1
(4) no operation

Packet 2:
(1) clear vblank event
(2) wait vblank event
(3) write register setting 2
(4) no operation

In your current design, you modify these two packet as:

Packet 1:
(1) clear vblank event
(2) wait vblank event
(3) write register setting 1
(4) Jump to packet 2 (modified)

Packet 2:
(1) no operation (modified)
(2) no operation (modified)
(3) write register setting 2
(4) no operation

So the register setting 1 and register setting 2 could be executed in
the same vblank period.

My suggestion is: when the client want to send packet 2, it 'abort'
packet 1 at first. The 'abort' means remove it from channel. In current
mailbox interface, mbox_free_channel() is most like abort function, but
my abort would keep the channel. So maybe you need to implement a new
mailbox interface which could remove packet in the channel. So the step
would be:

(1) Client generate packet 1 which include write register setting 1
(2) Client send packet 1 to channel A

When client want to send register setting 2,

(3) Client abort channel A
(4) Client generate packet 2 which include write register setting 1 & 2
(5) Client send packet 2 to channel A

Once you have the abort function, you could use the queue mechanism in
mailbox core instead of implementing your own.

For the client which have the atomic requirement, it also need not to
implement a list to keep what command have not executed. So the abort
interface would make client and controller much simpler.

Regards,
CK

> +}
> +
> +static void cmdq_task_exec_done(struct cmdq_task *task, bool err)
> +{
> +	struct device *dev = task->cmdq->mbox.dev;
> +	struct cmdq_cb_data cmdq_cb_data;
> +
> +	dma_unmap_single(dev, task->pa_base, task->pkt->cmd_buf_size,
> +			 DMA_TO_DEVICE);
> +	if (task->pkt->cb.cb) {
> +		cmdq_cb_data.err = err;
> +		cmdq_cb_data.data = task->pkt->cb.data;
> +		task->pkt->cb.cb(cmdq_cb_data);
> +	}
> +	list_del(&task->list_entry);
> +}
> +
> +static void cmdq_task_handle_error(struct cmdq_task *task)
> +{
> +	struct cmdq_thread *thread = task->thread;
> +	struct cmdq_task *next_task;
> +
> +	dev_err(task->cmdq->mbox.dev, "task 0x%p error\n", task);
> +	WARN_ON(cmdq_thread_suspend(task->cmdq, thread) < 0);
> +	next_task = list_first_entry_or_null(&thread->task_busy_list,
> +			struct cmdq_task, list_entry);
> +	if (next_task)
> +		writel(next_task->pa_base, thread->base + CMDQ_THR_CURR_ADDR);
> +	cmdq_thread_resume(thread);
> +}
> +
> +static void cmdq_thread_irq_handler(struct cmdq *cmdq,
> +				    struct cmdq_thread *thread)
> +{
> +	struct cmdq_task *task, *tmp, *curr_task = NULL;
> +	u32 curr_pa, irq_flag, task_end_pa;
> +	bool err;
> +
> +	irq_flag = readl(thread->base + CMDQ_THR_IRQ_STATUS);
> +	writel(~irq_flag, thread->base + CMDQ_THR_IRQ_STATUS);
> +
> +	/*
> +	 * When ISR call this function, another CPU core could run
> +	 * "release task" right before we acquire the spin lock, and thus
> +	 * reset / disable this GCE thread, so we need to check the enable
> +	 * bit of this GCE thread.
> +	 */
> +	if (!(readl(thread->base + CMDQ_THR_ENABLE_TASK) & CMDQ_THR_ENABLED))
> +		return;
> +
> +	if (irq_flag & CMDQ_THR_IRQ_ERROR)
> +		err = true;
> +	else if (irq_flag & CMDQ_THR_IRQ_DONE)
> +		err = false;
> +	else
> +		return;
> +
> +	curr_pa = readl(thread->base + CMDQ_THR_CURR_ADDR);
> +
> +	list_for_each_entry_safe(task, tmp, &thread->task_busy_list,
> +				 list_entry) {
> +		task_end_pa = task->pa_base + task->pkt->cmd_buf_size;
> +		if (curr_pa >= task->pa_base && curr_pa < task_end_pa)
> +			curr_task = task;
> +
> +		if (!curr_task || curr_pa == task_end_pa - CMDQ_INST_SIZE) {
> +			cmdq_task_exec_done(task, false);
> +			kfree(task);
> +		} else if (err) {
> +			cmdq_task_exec_done(task, true);
> +			cmdq_task_handle_error(curr_task);
> +			kfree(task);
> +		}
> +
> +		if (curr_task)
> +			break;
> +	}
> +
> +	if (list_empty(&thread->task_busy_list)) {
> +		cmdq_thread_disable(cmdq, thread);
> +		clk_disable(cmdq->clock);
> +	} else {
> +		mod_timer(&thread->timeout,
> +			  jiffies + msecs_to_jiffies(CMDQ_TIMEOUT_MS));
> +	}
> +}
> +
> +static irqreturn_t cmdq_irq_handler(int irq, void *dev)
> +{
> +	struct cmdq *cmdq = dev;
> +	unsigned long irq_status, flags = 0L;
> +	int bit;
> +
> +	irq_status = readl(cmdq->base + CMDQ_CURR_IRQ_STATUS) & CMDQ_IRQ_MASK;
> +	if (!(irq_status ^ CMDQ_IRQ_MASK))
> +		return IRQ_NONE;
> +
> +	for_each_clear_bit(bit, &irq_status, fls(CMDQ_IRQ_MASK)) {
> +		struct cmdq_thread *thread = &cmdq->thread[bit];
> +
> +		spin_lock_irqsave(&thread->chan->lock, flags);
> +		cmdq_thread_irq_handler(cmdq, thread);
> +		spin_unlock_irqrestore(&thread->chan->lock, flags);
> +	}
> +	return IRQ_HANDLED;
> +}
> +
> +static void cmdq_thread_handle_timeout(struct timer_list *t)
> +{
> +	struct cmdq_thread *thread = from_timer(thread, t, timeout);
> +	struct cmdq *cmdq = container_of(thread->chan->mbox, struct cmdq, mbox);
> +	struct cmdq_task *task, *tmp;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&thread->chan->lock, flags);
> +	WARN_ON(cmdq_thread_suspend(cmdq, thread) < 0);
> +
> +	/*
> +	 * Although IRQ is disabled, GCE continues to execute.
> +	 * It may have pending IRQ before GCE thread is suspended,
> +	 * so check this condition again.
> +	 */
> +	cmdq_thread_irq_handler(cmdq, thread);
> +
> +	if (list_empty(&thread->task_busy_list)) {
> +		cmdq_thread_resume(thread);
> +		spin_unlock_irqrestore(&thread->chan->lock, flags);
> +		return;
> +	}
> +
> +	dev_err(cmdq->mbox.dev, "timeout\n");
> +	list_for_each_entry_safe(task, tmp, &thread->task_busy_list,
> +				 list_entry) {
> +		cmdq_task_exec_done(task, true);
> +		kfree(task);
> +	}
> +
> +	cmdq_thread_resume(thread);
> +	cmdq_thread_disable(cmdq, thread);
> +	clk_disable(cmdq->clock);
> +	spin_unlock_irqrestore(&thread->chan->lock, flags);
> +}
> +
> +static int cmdq_suspend(struct device *dev)
> +{
> +	struct cmdq *cmdq = dev_get_drvdata(dev);
> +	struct cmdq_thread *thread;
> +	int i;
> +	bool task_running = false;
> +
> +	cmdq->suspended = true;
> +
> +	for (i = 0; i < ARRAY_SIZE(cmdq->thread); i++) {
> +		thread = &cmdq->thread[i];
> +		if (!list_empty(&thread->task_busy_list)) {
> +			task_running = true;
> +			break;
> +		}
> +	}
> +
> +	if (task_running)
> +		dev_warn(dev, "exist running task(s) in suspend\n");
> +
> +	clk_unprepare(cmdq->clock);
> +	return 0;
> +}
> +
> +static int cmdq_resume(struct device *dev)
> +{
> +	struct cmdq *cmdq = dev_get_drvdata(dev);
> +
> +	WARN_ON(clk_prepare(cmdq->clock) < 0);
> +	cmdq->suspended = false;
> +	return 0;
> +}
> +
> +static int cmdq_remove(struct platform_device *pdev)
> +{
> +	struct cmdq *cmdq = platform_get_drvdata(pdev);
> +
> +	mbox_controller_unregister(&cmdq->mbox);
> +	clk_unprepare(cmdq->clock);
> +	return 0;
> +}
> +
> +static int cmdq_mbox_send_data(struct mbox_chan *chan, void *data)
> +{
> +	cmdq_task_exec(data, chan->con_priv);
> +	return 0;
> +}
> +
> +static int cmdq_mbox_startup(struct mbox_chan *chan)
> +{
> +	return 0;
> +}
> +
> +static void cmdq_mbox_shutdown(struct mbox_chan *chan)
> +{
> +}
> +
> +static bool cmdq_mbox_last_tx_done(struct mbox_chan *chan)
> +{
> +	return true;
> +}
> +
> +static const struct mbox_chan_ops cmdq_mbox_chan_ops = {
> +	.send_data = cmdq_mbox_send_data,
> +	.startup = cmdq_mbox_startup,
> +	.shutdown = cmdq_mbox_shutdown,
> +	.last_tx_done = cmdq_mbox_last_tx_done,
> +};
> +
> +static struct mbox_chan *cmdq_xlate(struct mbox_controller *mbox,
> +		const struct of_phandle_args *sp)
> +{
> +	int ind = sp->args[0];
> +	struct cmdq_thread *thread;
> +
> +	if (ind >= mbox->num_chans)
> +		return ERR_PTR(-EINVAL);
> +
> +	thread = mbox->chans[ind].con_priv;
> +	thread->atomic_exec = (sp->args[1] != 0);
> +	thread->chan = &mbox->chans[ind];
> +
> +	return &mbox->chans[ind];
> +}
> +
> +static int cmdq_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct resource *res;
> +	struct cmdq *cmdq;
> +	int err, i;
> +
> +	cmdq = devm_kzalloc(dev, sizeof(*cmdq), GFP_KERNEL);
> +	if (!cmdq)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	cmdq->base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(cmdq->base)) {
> +		dev_err(dev, "failed to ioremap gce\n");
> +		return PTR_ERR(cmdq->base);
> +	}
> +
> +	cmdq->irq = platform_get_irq(pdev, 0);
> +	if (!cmdq->irq) {
> +		dev_err(dev, "failed to get irq\n");
> +		return -EINVAL;
> +	}
> +	err = devm_request_irq(dev, cmdq->irq, cmdq_irq_handler, IRQF_SHARED,
> +			       "mtk_cmdq", cmdq);
> +	if (err < 0) {
> +		dev_err(dev, "failed to register ISR (%d)\n", err);
> +		return err;
> +	}
> +
> +	dev_dbg(dev, "cmdq device: addr:0x%p, va:0x%p, irq:%d\n",
> +		dev, cmdq->base, cmdq->irq);
> +
> +	cmdq->clock = devm_clk_get(dev, "gce");
> +	if (IS_ERR(cmdq->clock)) {
> +		dev_err(dev, "failed to get gce clk\n");
> +		return PTR_ERR(cmdq->clock);
> +	}
> +
> +	cmdq->mbox.dev = dev;
> +	cmdq->mbox.chans = devm_kcalloc(dev, CMDQ_THR_MAX_COUNT,
> +					sizeof(*cmdq->mbox.chans), GFP_KERNEL);
> +	if (!cmdq->mbox.chans)
> +		return -ENOMEM;
> +
> +	cmdq->mbox.num_chans = CMDQ_THR_MAX_COUNT;
> +	cmdq->mbox.ops = &cmdq_mbox_chan_ops;
> +	cmdq->mbox.of_xlate = cmdq_xlate;
> +
> +	/* make use of TXDONE_BY_ACK */
> +	cmdq->mbox.txdone_irq = false;
> +	cmdq->mbox.txdone_poll = false;
> +
> +	for (i = 0; i < ARRAY_SIZE(cmdq->thread); i++) {
> +		cmdq->thread[i].base = cmdq->base + CMDQ_THR_BASE +
> +				CMDQ_THR_SIZE * i;
> +		INIT_LIST_HEAD(&cmdq->thread[i].task_busy_list);
> +		timer_setup(&cmdq->thread[i].timeout,
> +				cmdq_thread_handle_timeout, 0);
> +		cmdq->mbox.chans[i].con_priv = &cmdq->thread[i];
> +	}
> +
> +	err = mbox_controller_register(&cmdq->mbox);
> +	if (err < 0) {
> +		dev_err(dev, "failed to register mailbox: %d\n", err);
> +		return err;
> +	}
> +
> +	platform_set_drvdata(pdev, cmdq);
> +	WARN_ON(clk_prepare(cmdq->clock) < 0);
> +
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops cmdq_pm_ops = {
> +	.suspend = cmdq_suspend,
> +	.resume = cmdq_resume,
> +};
> +
> +static const struct of_device_id cmdq_of_ids[] = {
> +	{.compatible = "mediatek,mt8173-gce",},
> +	{}
> +};
> +
> +static struct platform_driver cmdq_drv = {
> +	.probe = cmdq_probe,
> +	.remove = cmdq_remove,
> +	.driver = {
> +		.name = "mtk_cmdq",
> +		.pm = &cmdq_pm_ops,
> +		.of_match_table = cmdq_of_ids,
> +	}
> +};
> +
> +builtin_platform_driver(cmdq_drv);
> diff --git a/include/linux/mailbox/mtk-cmdq-mailbox.h b/include/linux/mailbox/mtk-cmdq-mailbox.h
> new file mode 100644
> index 0000000..c463f2f
> --- /dev/null
> +++ b/include/linux/mailbox/mtk-cmdq-mailbox.h
> @@ -0,0 +1,77 @@
> +/*
> + * Copyright (c) 2015 MediaTek Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#ifndef __MTK_CMDQ_MAILBOX_H__
> +#define __MTK_CMDQ_MAILBOX_H__
> +
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +
> +#define CMDQ_INST_SIZE			8 /* instruction is 64-bit */
> +#define CMDQ_SUBSYS_SHIFT		16
> +#define CMDQ_OP_CODE_SHIFT		24
> +#define CMDQ_JUMP_PASS			CMDQ_INST_SIZE
> +
> +#define CMDQ_WFE_UPDATE			BIT(31)
> +#define CMDQ_WFE_WAIT			BIT(15)
> +#define CMDQ_WFE_WAIT_VALUE		0x1
> +
> +/*
> + * CMDQ_CODE_MASK:
> + *   set write mask
> + *   format: op mask
> + * CMDQ_CODE_WRITE:
> + *   write value into target register
> + *   format: op subsys address value
> + * CMDQ_CODE_JUMP:
> + *   jump by offset
> + *   format: op offset
> + * CMDQ_CODE_WFE:
> + *   wait for event and clear
> + *   it is just clear if no wait
> + *   format: [wait]  op event update:1 to_wait:1 wait:1
> + *           [clear] op event update:1 to_wait:0 wait:0
> + * CMDQ_CODE_EOC:
> + *   end of command
> + *   format: op irq_flag
> + */
> +enum cmdq_code {
> +	CMDQ_CODE_MASK = 0x02,
> +	CMDQ_CODE_WRITE = 0x04,
> +	CMDQ_CODE_JUMP = 0x10,
> +	CMDQ_CODE_WFE = 0x20,
> +	CMDQ_CODE_EOC = 0x40,
> +};
> +
> +struct cmdq_cb_data {
> +	bool	err;
> +	void	*data;
> +};
> +
> +typedef void (*cmdq_async_flush_cb)(struct cmdq_cb_data data);
> +
> +struct cmdq_task_cb {
> +	cmdq_async_flush_cb	cb;
> +	void			*data;
> +};
> +
> +struct cmdq_pkt {
> +	void			*va_base;
> +	dma_addr_t		pa_base;
> +	size_t			cmd_buf_size; /* command occupied size */
> +	size_t			buf_size; /* real buffer size */
> +	struct cmdq_task_cb	cb;
> +};
> +
> +#endif /* __MTK_CMDQ_MAILBOX_H__ */