linux-kernel - Re: [PATCH v14 2/4] CMDQ: Mediatek CMDQ driver

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Date:   Fri, 30 Sep 2016 17:47:09 +0800
From:   Horng-Shyang Liao <hs.liao@...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>,
        "Daniel Kurtz" <djkurtz@...omium.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>,
        Sascha Hauer <kernel@...gutronix.de>,
        "Philipp Zabel" <p.zabel@...gutronix.de>,
        Nicolas Boichat <drinkcat@...omium.org>,
        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@...iatek.com>
Subject: Re: [PATCH v14 2/4] CMDQ: Mediatek CMDQ driver

On Fri, 2016-09-30 at 17:11 +0800, CK Hu wrote:
> Hi, HS:
> 
> One comment inline
> 
> On Fri, 2016-09-30 at 16:56 +0800, Horng-Shyang Liao wrote:
> > Hi CK,
> > 
> > Please see my inline reply.
> > 
> > On Fri, 2016-09-30 at 11:06 +0800, CK Hu wrote:
> > > Hi, HS:
> > > 
> > > On Mon, 2016-09-05 at 09:44 +0800, HS Liao wrote:
> > > > This patch is first version of Mediatek Command Queue(CMDQ) driver. The
> > > > CMDQ is used to help write registers with critical time limitation,
> > > > such as updating display configuration during the vblank. It controls
> > > > Global Command Engine (GCE) hardware to achieve this requirement.
> > > > Currently, CMDQ only supports display related hardwares, but we expect
> > > > it can be extended to other hardwares for future requirements.
> > > > 
> > > > Signed-off-by: HS Liao <hs.liao@...iatek.com>
> > > > Signed-off-by: CK Hu <ck.hu@...iatek.com>
> > > > ---
> > > 
> > > [snip...]
> > > 
> > > > +
> > > > +struct cmdq_task {
> > > > +	struct cmdq		*cmdq;
> > > > +	struct list_head	list_entry;
> > > > +	void			*va_base;
> > > > +	dma_addr_t		pa_base;
> > > > +	size_t			cmd_buf_size; /* command occupied size */
> > > > +	size_t			buf_size; /* real buffer size */
> > > > +	bool			finalized;
> > > > +	struct cmdq_thread	*thread;
> > > 
> > > I think thread info could be removed from cmdq_task. Only
> > > cmdq_task_handle_error() and cmdq_task_insert_into_thread() use
> > > task->thread and caller of both function has the thread info. So you
> > > could just pass thread info into these two function and remove thread
> > > info in cmdq_task.
> > 
> > This modification will remove 1 pointer but add 2 pointers. Moreover,
> > more pointers will need to be delivered between functions for future
> > extension. IMHO, it would be better to keep thread pointer inside
> > cmdq_task.
> > 
> > > > +	struct cmdq_task_cb	cb;
> > > 
> > > I think this callback function is equal to mailbox client tx_done
> > > callback. It's better to use already-defined interface rather than
> > > creating your own.
> > 
> > This is because CMDQ driver allows different callback functions for
> > different tasks, but mailbox only allows one callback function per
> > channel. But, I think I can add a wrapper for tx_done to call CMDQ
> > callback functions. So, I will use tx_done in CMDQ v15.
> 
> Up to now, one callback function for one channel is enough for DRM. So
> 'different callback function for different sent-message' looks like an
> advanced function. Maybe you should not include it in first patch. 
> 
> Regards,
> CK

Hi CK,

OK. I will do it.

Thanks,
HS

[snip...]