linux-kernel - Re: [PATCH 1/3] drm/mediatek: Dynamically allocate CMDQ and use helper functions

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Message-ID: <7175ec117988657c2fb7bf6d50b67d60038e3a54.camel@mediatek.com>
Date:   Thu, 3 Aug 2023 08:37:00 +0000
From:   CK Hu (胡俊光) <ck.hu@...iatek.com>
To:     "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
CC:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "kernel@...labora.com" <kernel@...labora.com>,
        "wenst@...omium.org" <wenst@...omium.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>
Subject: Re: [PATCH 1/3] drm/mediatek: Dynamically allocate CMDQ and use
 helper functions

Hi, Angelo:

On Thu, 2023-08-03 at 10:25 +0200, AngeloGioacchino Del Regno wrote:
> Il 03/08/23 08:28, CK Hu (胡俊光) ha scritto:
> > Hi, Angelo:
> > 
> > On Wed, 2023-08-02 at 12:41 +0200, AngeloGioacchino Del Regno
> > wrote:
> > > Il 02/08/23 08:24, CK Hu (胡俊光) ha scritto:
> > > > Hi, Angelo:
> > > > 
> > > > On Fri, 2023-06-23 at 11:49 +0200, AngeloGioacchino Del Regno
> > > > wrote:
> > > > >    	
> > > > > External email : Please do not click links or open
> > > > > attachments
> > > > > until
> > > > > you have verified the sender or the content.
> > > > >    Instead of stack allocating the cmdq_client and
> > > > > cmdq_handle
> > > > > structures
> > > > > switch them to pointers, allowing us to migrate this driver
> > > > > to
> > > > > use
> > > > > the
> > > > > common functions provided by mtk-cmdq-helper.
> > > > > In order to do this, it was also necessary to add a `priv`
> > > > > pointer to
> > > > > struct cmdq_client, as that's used to pass (in this case) a
> > > > > mtk_crtc
> > > > > handle to the ddp_cmdq_cb() mailbox RX callback function.
> > > > > 
> > > > > Signed-off-by: AngeloGioacchino Del Regno <
> > > > > angelogioacchino.delregno@...labora.com>
> > > > > ---
> > > > >    drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 107 +++++++-----
> > > > > ---
> > > > > -------
> > > > > --
> > > > >    include/linux/soc/mediatek/mtk-cmdq.h   |   1 +
> > > > >    2 files changed, 32 insertions(+), 76 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > > > > b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > > > > index 0df62b076f49..b63289ab6787 100644
> > > > > --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > > > > +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> > > > > @@ -50,8 +50,8 @@ struct mtk_drm_crtc {
> > > > >    	bool				pending_async_planes;
> > > > >    
> > > > >    #if IS_REACHABLE(CONFIG_MTK_CMDQ)
> > > > > -	struct cmdq_client		cmdq_client;
> > > > > -	struct cmdq_pkt			cmdq_handle;
> > > > > +	struct cmdq_client		*cmdq_client;
> > > > > +	struct cmdq_pkt			*cmdq_handle;
> > > > >    	u32				cmdq_event;
> > > > >    	u32				cmdq_vblank_cnt;
> > > > >    	wait_queue_head_t		cb_blocking_queue;
> > > > > @@ -108,47 +108,6 @@ static void
> > > > > mtk_drm_finish_page_flip(struct
> > > > > mtk_drm_crtc *mtk_crtc)
> > > > >    	}
> > > > >    }
> > > > >    
> > > > > -#if IS_REACHABLE(CONFIG_MTK_CMDQ)
> > > > > -static int mtk_drm_cmdq_pkt_create(struct cmdq_client
> > > > > *client,
> > > > > struct cmdq_pkt *pkt,
> > > > > -				   size_t size)
> > > > > -{
> > > > > -	struct device *dev;
> > > > > -	dma_addr_t dma_addr;
> > > > > -
> > > > > -	pkt->va_base = kzalloc(size, GFP_KERNEL);
> > > > > -	if (!pkt->va_base) {
> > > > > -		kfree(pkt);
> > > > > -		return -ENOMEM;
> > > > > -	}
> > > > > -	pkt->buf_size = size;
> > > > > -	pkt->cl = (void *)client;
> > > > 
> > > > I have a plan to remove cl in struct cmdq_pkt. But this
> > > > modification
> > > > would make this plan more difficult. So I would pending this
> > > > patch
> > > > until cl is removed from struct cmdq_pkt.
> > > > 
> > > 
> > > I think that this ifdef cleanup is more urgent than the removal
> > > of
> > > `cl` from
> > > struct cmdq_pkt, as those ifdefs shouldn't have reached upstream
> > > in
> > > the first
> > > place, don't you agree?
> > 
> > I think removing ifdefs and using helper function are different
> > things.
> > You could remove ifdefs and keep mtk_drm_cmdq_pkt_create().
> > 
> 
> I chose to do it like that because this function would otherwise be a
> 100% duplicate of the related cmdq helper :-)

Removing cl would change the interface of cmdq_pkt_create(). And this
is related to different maintainer's tree. So it would be a long time
to process. For you, only removing ifdes is urgent, so use
cmdq_pkt_create() is not urgent. So let's keep
mtk_drm_cmdq_pkt_create() and you could remove ifdefs.

Regards,
CK

> 
> 
> > Regards,
> > CK
> > 
> > > 
> > > Regards,
> > > Angelo
> > > 
> 
>