linux-kernel - Re: FW: [PATCH v20 2/4] mailbox: mediatek: Add Mediatek CMDQ driver

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Message-ID: <CABb+yY02S=+00mY-NTkJUBPiVruYdf0xuovKomehUxLNOQPLuA@mail.gmail.com>
Date:   Thu, 18 Jan 2018 13:31:24 +0530
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     houlong wei <houlong.wei@...iatek.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        ", Matthias Brugger" <matthias.bgg@...il.com>,
        ", Daniel Kurtz" <djkurtz@...omium.org>,
        ", Sascha Hauer" <s.hauer@...gutronix.de>,
        ", Devicetree List" <devicetree@...r.kernel.org>,
        ", Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        ", linux-arm-kernel@...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>,
        ", CK Hu" <ck.hu@...iatek.com>,
        ", Cawa Cheng" <cawa.cheng@...iatek.com>,
        ", Bibby Hsieh" <Bibby.Hsieh@...iatek.com>,
        ", YT Shen" <yt.shen@...iatek.com>,
        ", Daoyuan Huang" <Daoyuan.Huang@...iatek.com>,
        ", Damon Chu" <damon.chu@...iatek.com>,
        ", Josh-YC Liu" <Josh-YC.Liu@...iatek.com>,
        ", Glory Hung" <glory.hung@...iatek.com>,
        ", Jiaguang Zhang" <Jiaguang.Zhang@...iatek.com>,
        ", Dennis-YC Hsieh" <Dennis-YC.Hsieh@...iatek.com>,
        ", Monica Wang" <monica.wang@...iatek.com>,
        ", Hs Liao" <hs.liao@...iatek.com>
Subject: Re: FW: [PATCH v20 2/4] mailbox: mediatek: Add Mediatek CMDQ driver

On Mon, Jan 8, 2018 at 2:08 PM, houlong wei <houlong.wei@...iatek.com> wrote:
> Hi Jassi,
>
> Sorry for reply so late.
> According to previous discussion, there are two methods to move
> dma_map_single() outside of spin_lock.
> (1) put in mtk-cmdq-helper.c, as described by HS on 2017-02-09.
>   > I think a trade-off solution is to put in mtk-cmdq-helper.c.
>   > Although it is a mailbox client, it is not a CMDQ client.
>   > We can include mailbox_controller.h in mtk-cmdq-helper.c (instead of
> mtk-cmdq.h), and then map dma at cmdq_pkt_flush_async before
> mbox_send_message.
>
>   > pkt->pa_base = dma_map_single(client->chan->mbox->dev, pkt->va_base,
>   >                              pkt->cmd_buf_size, DMA_TO_DEVICE);
> (2) schedule a tasklet in send_data().
>
> After internal discussion with HS and other experts, now we prefer
> method (1).
> How do you think about it?
>
I don't exactly see how you mean but please remember send_data()
callback is supposed to be atomic ... it is protected by
spin_lock_irqsave/restore in drivers/mailbox/mailbox.c:msg_submit()

BTW, how many requests max can be queued in the GCE h/w buffer?
And since it's been over a year now, could you please resubmit after
checking for checkpatch with the --strict option?

Thanks.