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From:   Jassi Brar <jassisinghbrar@gmail.com>
Date:   Thu, 18 Jan 2018 13:31:24 +0530
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Subject: Re: FW: [PATCH v20 2/4] mailbox: mediatek: Add Mediatek CMDQ driver
To:     houlong wei <houlong.wei@mediatek.com>
Cc:     Rob Herring <robh+dt@kernel.org>,
        ", Matthias Brugger" <matthias.bgg@gmail.com>,
        ", Daniel Kurtz" <djkurtz@chromium.org>,
        ", Sascha Hauer" <s.hauer@pengutronix.de>,
        ", Devicetree List" <devicetree@vger.kernel.org>,
        ", Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
        ", linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, srv_heupstream" 
        <srv_heupstream@mediatek.com>,
        ", Sascha Hauer" <kernel@pengutronix.de>,
        ", Philipp Zabel" <p.zabel@pengutronix.de>,
        ", Nicolas Boichat" <drinkcat@chromium.org>,
        ", CK Hu" <ck.hu@mediatek.com>,
        ", 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>
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On Mon, Jan 8, 2018 at 2:08 PM, houlong wei <houlong.wei@mediatek.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.