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

[CK Hu <ck.hu@mediatek.com>]

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@mediatek.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.

> +
> +	/* 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

> +
> +	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

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