linux-kernel - Re: [PATCH v22 4/4] soc: mediatek: Add Mediatek CMDQ helper

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Date:   Fri, 29 Jun 2018 17:22:03 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     houlong wei <houlong.wei@...iatek.com>
CC:     Jassi Brar <jassisinghbrar@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Daniel Kurtz <djkurtz@...omium.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        srv_heupstream <srv_heupstream@...iatek.com>,
        Sascha Hauer <kernel@...gutronix.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "Nicolas Boichat" <drinkcat@...omium.org>,
        Bibby Hsieh (謝濟遠) 
        <Bibby.Hsieh@...iatek.com>,
        YT Shen (沈岳霆) 
        <Yt.Shen@...iatek.com>,
        Daoyuan Huang (黃道原) 
        <Daoyuan.Huang@...iatek.com>,
        Jiaguang Zhang (张加广) 
        <Jiaguang.Zhang@...iatek.com>,
        Dennis-YC Hsieh (謝宇哲) 
        <Dennis-YC.Hsieh@...iatek.com>,
        Monica Wang (王孟婷) 
        <monica.wang@...iatek.com>,
        Hs Liao (廖宏祥) 
        <Hs.Liao@...iatek.com>,
        Ginny Chen (陳治傑) 
        <ginny.chen@...iatek.com>,
        Enzhu Wang (王恩柱) 
        <enzhu.wang@...iatek.com>
Subject: Re: [PATCH v22 4/4] soc: mediatek: Add Mediatek CMDQ helper

Hi, Houlong:

On Fri, 2018-06-29 at 07:32 +0800, houlong wei wrote:
> On Thu, 2018-06-28 at 18:41 +0800, CK Hu wrote:
> > Hi, Houlong:
> > 
> > Some inline comment.
> > 
> > On Wed, 2018-06-27 at 19:16 +0800, Houlong Wei wrote:
> > > Add Mediatek CMDQ helper to create CMDQ packet and assemble GCE op code.
> > > 
> > > Signed-off-by: Houlong Wei <houlong.wei@...iatek.com>
> > > Signed-off-by: HS Liao <hs.liao@...iatek.com>
> > > ---
> > >  drivers/soc/mediatek/Kconfig           |   12 ++
> > >  drivers/soc/mediatek/Makefile          |    1 +
> > >  drivers/soc/mediatek/mtk-cmdq-helper.c |  258 ++++++++++++++++++++++++++++++++
> > >  include/linux/soc/mediatek/mtk-cmdq.h  |  132 ++++++++++++++++
> > >  4 files changed, 403 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
> > >  
> > 

[...]

> > > +
> > > +static int cmdq_pkt_finalize(struct cmdq_pkt *pkt)
> > > +{
> > > +	int err;
> > > +
> > > +	if (cmdq_pkt_is_finalized(pkt))
> > > +		return 0;
> > > +
> > > +	/* insert EOC and generate IRQ for each command iteration */
> > > +	err = cmdq_pkt_append_command(pkt, CMDQ_CODE_EOC, 0, CMDQ_EOC_IRQ_EN);
> > > +	if (err < 0)
> > > +		return err;
> > > +
> > > +	/* JUMP to end */
> > > +	err = cmdq_pkt_append_command(pkt, CMDQ_CODE_JUMP, 0, CMDQ_JUMP_PASS);
> > > +	if (err < 0)
> > > +		return err;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +int cmdq_pkt_flush_async(struct cmdq_client *client, struct cmdq_pkt *pkt,
> > > +			 cmdq_async_flush_cb cb, void *data)
> > > +{
> > > +	int err;
> > > +	struct device *dev;
> > > +	dma_addr_t dma_addr;
> > > +
> > > +	err = cmdq_pkt_finalize(pkt);
> > > +	if (err < 0)
> > > +		return err;
> > > +
> > > +	dev = client->chan->mbox->dev;
> > > +	dma_addr = dma_map_single(dev, pkt->va_base, pkt->cmd_buf_size,
> > > +		DMA_TO_DEVICE);
> > 
> > You map here, but I could not find unmap, so the unmap should be done in
> > client driver. I would prefer a symmetric map/unmap which means that
> > both map and unmap are done in client driver. I think you put map here
> > because you should map after finalize. 
> 
> The unmap is done before callback to client, in function
> cmdq_task_exec_done, mtk-cmdq-mailbox.c.

You put unmap in mailbox controller, and map here (here would be mailbox
client), so this is not symmetric. If the code is asymmetric, it's easy
to cause bug and not easy to maintain. So I would like move both
map/unmap to client driver.

> 
> > Therefore, export
> > cmdq_pkt_finalize() to client driver and let client do finalize, so
> > there is no finalize in flush function. This method have a benefit that
> > if client reuse command buffer, it need not to map/unmap frequently.
> 
> If client reuse command buffer or cmdq_pkt(command queue packet), client
> will add new commands to the cmdq_pkt, so map/unmap are necessary for
> each cmdq_pkt flush.

If the buffer size is 4K bytes, client driver could map the whole 4K at
initialization. Before it write new command, it call
dma_sync_single_for_cpu(), after it write new command, it call
dma_sync_single_for_device(). And then it could flush this buffer to
mailbox controller. So client driver just call dma sync function when it
reuse the command buffer. dma sync function is much lightweight then dma
map because map would search the memory area which could be mapped.

Regards,
CK

> 
> > 
> > Regards,
> > CK
> > 
> > > +	if (dma_mapping_error(dev, dma_addr)) {
> > > +		dev_err(client->chan->mbox->dev, "dma map failed\n");
> > > +		return -ENOMEM;
> > > +	}
> > > +
> > > +	pkt->pa_base = dma_addr;
> > > +	pkt->cb.cb = cb;
> > > +	pkt->cb.data = data;
> > > +
> > > +	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 = data.data;
> > > +
> > > +	cmplt->err = data.err;
> > > +	complete(&cmplt->cmplt);
> > > +}
> > > +
> > > +int cmdq_pkt_flush(struct cmdq_client *client, struct cmdq_pkt *pkt)
> > > +{
> > > +	struct cmdq_flush_completion cmplt;
> > > +	int err;
> > > +
> > > +	init_completion(&cmplt.cmplt);
> > > +	err = cmdq_pkt_flush_async(client, 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);
> > 
> > [...]
> > 
> > 
> 
>