linux-kernel - Re: [PATCH v2 12/14] soc: mediatek: cmdq: add loop function

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Date:   Thu, 12 Dec 2019 09:37:32 +0800
From:   Dennis-YC Hsieh <dennis-yc.hsieh@...iatek.com>
To:     CK Hu <ck.hu@...iatek.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <wsd_upstream@...iatek.com>,
        Bibby Hsieh <bibby.hsieh@...iatek.com>,
        Houlong Wei <houlong.wei@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 12/14] soc: mediatek: cmdq: add loop function

Hi CK,

On Wed, 2019-12-11 at 09:48 +0800, CK Hu wrote:
> Hi, Dennis:
> 
> On Wed, 2019-11-27 at 09:58 +0800, Dennis YC Hsieh wrote:
> > Add finalize loop function in cmdq helper functions which loop whole pkt
> > in gce hardware thread without cpu operation.
> > 
> > Signed-off-by: Dennis YC Hsieh <dennis-yc.hsieh@...iatek.com>
> > ---
> >  drivers/soc/mediatek/mtk-cmdq-helper.c | 22 ++++++++++++++++++++++
> >  include/linux/soc/mediatek/mtk-cmdq.h  |  8 ++++++++
> >  2 files changed, 30 insertions(+)
> > 
> > diff --git a/drivers/soc/mediatek/mtk-cmdq-helper.c b/drivers/soc/mediatek/mtk-cmdq-helper.c
> > index 38e0c13e1922..10a9b4481e58 100644
> > --- a/drivers/soc/mediatek/mtk-cmdq-helper.c
> > +++ b/drivers/soc/mediatek/mtk-cmdq-helper.c
> > @@ -414,6 +414,28 @@ int cmdq_pkt_finalize(struct cmdq_pkt *pkt)
> >  }
> >  EXPORT_SYMBOL(cmdq_pkt_finalize);
> >  
> > +int cmdq_pkt_finalize_loop(struct cmdq_pkt *pkt)
> > +{
> > +	struct cmdq_client *cl = pkt->cl;
> > +	struct cmdq_instruction inst = { {0} };
> > +	int err;
> > +
> > +	/* insert EOC and generate IRQ for each command iteration */
> > +	inst.op = CMDQ_CODE_EOC;
> > +	err = cmdq_pkt_append_command(pkt, inst);
> > +	if (err < 0)
> > +		return err;
> 
> It looks like you want a pkt execute command repeatedly, but why do you
> repeatedly trigger IRQ? This IRQ would do nothing because this pkt would
> never finish.
> 

see following section

> > +
> > +	/* JUMP abaolute to begin */
> > +	inst.op = CMDQ_CODE_JUMP;
> > +	inst.offset = 1;
> > +	inst.value = pkt->pa_base >> cmdq_mbox_shift(cl->chan);
> > +	err = cmdq_pkt_append_command(pkt, inst);
> 
> Why not just export this function as cmdq_pkt_jump()? Let client decide
> where to jump would be more flexible.
> 
> Regards,
> CK
> 

ok, I will remove this part and expose cmdq_pkt_jump()


Regards,
Dennis

> > +
> > +	return err;
> > +}
> > +EXPORT_SYMBOL(cmdq_pkt_finalize_loop);
> > +
> >  static void cmdq_pkt_flush_async_cb(struct cmdq_cb_data data)
> >  {
> >  	struct cmdq_pkt *pkt = (struct cmdq_pkt *)data.data;
> > diff --git a/include/linux/soc/mediatek/mtk-cmdq.h b/include/linux/soc/mediatek/mtk-cmdq.h
> > index 998bc90f9da9..d15d8c941992 100644
> > --- a/include/linux/soc/mediatek/mtk-cmdq.h
> > +++ b/include/linux/soc/mediatek/mtk-cmdq.h
> > @@ -212,6 +212,14 @@ int cmdq_pkt_assign(struct cmdq_pkt *pkt, u16 reg_idx, u32 value);
> >   */
> >  int cmdq_pkt_finalize(struct cmdq_pkt *pkt);
> >  
> > +/**
> > + * cmdq_pkt_finalize_loop() - Append EOC and jump command to loop pkt.
> > + * @pkt:	the CMDQ packet
> > + *
> > + * Return: 0 for success; else the error code is returned
> > + */
> > +int cmdq_pkt_finalize_loop(struct cmdq_pkt *pkt);
> > +
> >  /**
> >   * cmdq_pkt_flush_async() - trigger CMDQ to asynchronously execute the CMDQ
> >   *                          packet and call back at the end of done packet
> 
>