Re: [PATCH 08/15] soc: mediatek: Add cmdq_pkt_finalize_loop to CMDQ driver

["Jason-JH Lin (林睿祥)" <Jason-JH.Lin@mediatek.com>]

On Tue, 2023-09-19 at 01:38 +0000, CK Hu (胡俊光) wrote:
> Hi, Jason:
> 
> On Tue, 2023-09-19 at 03:21 +0800, Jason-JH.Lin wrote:
> > Add cmdq_pkt_finalize_loop to CMDQ driver.
> > 
> > cmdq_pkt_finalize_loop appends end of command(EOC) instruction and
> > jump to start of command buffer instruction to make the command
> > buffer loopable.
> > 
> > Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
> > ---
> >  drivers/soc/mediatek/mtk-cmdq-helper.c | 23
> > +++++++++++++++++++++++
> >  include/linux/soc/mediatek/mtk-cmdq.h  |  8 ++++++++
> >  2 files changed, 31 insertions(+)
> > 
> > diff --git a/drivers/soc/mediatek/mtk-cmdq-helper.c
> > b/drivers/soc/mediatek/mtk-cmdq-helper.c
> > index 4be2a18a4a02..bbb127620bb3 100644
> > --- a/drivers/soc/mediatek/mtk-cmdq-helper.c
> > +++ b/drivers/soc/mediatek/mtk-cmdq-helper.c
> > @@ -475,6 +475,29 @@ int cmdq_pkt_finalize(struct cmdq_pkt *pkt)
> >  }
> >  EXPORT_SYMBOL(cmdq_pkt_finalize);
> >  
> > +int cmdq_pkt_finalize_loop(struct cmdq_pkt *pkt)
> > +{
> > +	struct cmdq_instruction inst = { {0} };
> > +	int err;
> > +
> > +	/* insert EOC and generate IRQ for each command iteration */
> > +	inst.op = CMDQ_CODE_EOC;
> > +	inst.value = CMDQ_EOC_IRQ_EN;
> > +	err = cmdq_pkt_append_command(pkt, inst);
> > +	if (err < 0)
> > +		return err;
> > +
> > +	/* JUMP to start of pkt */
> > +	err = cmdq_pkt_jump(pkt, pkt->pa_base);
> > +	if (err < 0)
> > +		return err;
> 
> Could you explain the case that a loop thread would trigger an
> interrupt? In DRM crc function, the loop thread need not to trigger
> interrupt, so I'm curious about this.
> 
The looping thread in DRM crc funtion is for update CRC value to DRAM
during every vblank event coming. It doesn't need to handle the
software flow after the EOC.

The looping thread in cmdq_sec_irq_notify_start() is waiting for every
CMDQ_SYNC_TOKEN_SEC_THR_EOF being set, that means the GCE in secure
world has finished all commands in a command buffer. Then it needs a
GCE irq to trigger secure mailbox rx_callback() to handle the task of
secure cmdq_pkt done in software.

Regards,
Jason-JH.Lin

> Regards,
> CK
> 
> > +
> > +	pkt->loop = true;
> > +
> > +	return err;
> > +}
> > +EXPORT_SYMBOL(cmdq_pkt_finalize_loop);
> > +
> >  int cmdq_pkt_flush_async(struct cmdq_pkt *pkt)
> >  {
> >  	int err;
> > diff --git a/include/linux/soc/mediatek/mtk-cmdq.h
> > b/include/linux/soc/mediatek/mtk-cmdq.h
> > index 837ad8656adc..38a8e47da338 100644
> > --- a/include/linux/soc/mediatek/mtk-cmdq.h
> > +++ b/include/linux/soc/mediatek/mtk-cmdq.h
> > @@ -323,6 +323,14 @@ int cmdq_pkt_jump(struct cmdq_pkt *pkt,
> > dma_addr_t addr);
> >   */
> >  int cmdq_pkt_finalize(struct cmdq_pkt *pkt);
> >  
> > +/**
> > + * cmdq_pkt_finalize_loop() - Append EOC and jump to start
> > command.
> > + * @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