linux-kernel - Re: [v9,2/3] drm/mediatek: implement the DSI hs packets aligned

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Date:   Tue, 18 Jan 2022 10:29:15 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     Andrzej Hajda <andrzej.hajda@...el.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        <chunkuang.hu@...nel.org>, <matthias.bgg@...il.com>,
        <narmstrong@...libre.com>, <robert.foss@...aro.org>,
        <daniel@...ll.ch>, <airlied@...ux.ie>, <p.zabel@...gutronix.de>
CC:     <xji@...logixsemi.com>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        Jitao Shi <jitao.shi@...iatek.com>
Subject: Re: [v9,2/3] drm/mediatek: implement the DSI hs packets aligned

Hello Andrzej,

Thanks for your review.
I will give the explanation for this in next version.

BRs,
Rex-BC hen

On Fri, 2022-01-14 at 12:11 +0100, Andrzej Hajda wrote:
> On 14.01.2022 11:20, Rex-BC Chen wrote:
> > Hello AngeloGioacchino,
> > 
> > Thanks for your review.
> > I will modify this in next version.
> > 
> > BRs,
> > Rex-BC Chen
> > 
> > On Fri, 2022-01-14 at 10:36 +0100, AngeloGioacchino Del Regno
> > wrote:
> > > Il 14/01/22 10:21, Rex-BC Chen ha scritto:
> > > > Some DSI RX devices require the packets on all lanes aligned at
> > > > the
> > > > end.
> > > > Otherwise, there will be some issues of shift or scroll for
> > > > screen.
> > > > 
> > > > Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
> > > > Signed-off-by: Rex-BC Chen <rex-bc.chen@...iatek.com>
> > > 
> > > Hello,
> > > thanks for the patch! However, there's something to improve...
> > > 
> > > > ---
> > > >    drivers/gpu/drm/mediatek/mtk_dsi.c | 12 ++++++++++++
> > > >    1 file changed, 12 insertions(+)
> > > > 
> > > > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > > b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > > index 5d90d2eb0019..ccdda15f5a66 100644
> > > > --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > > +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > > @@ -195,6 +195,8 @@ struct mtk_dsi {
> > > >    	struct clk *hs_clk;
> > > >    
> > > >    	u32 data_rate;
> > > > +	/* force dsi line end without dsi_null data */
> > > > +	bool hs_packet_end_aligned;
> > > 
> > > There's no need to introduce a new variable here...
> > > >    
> > > >    	unsigned long mode_flags;
> > > >    	enum mipi_dsi_pixel_format format;
> > > > @@ -500,6 +502,13 @@ static void
> > > > mtk_dsi_config_vdo_timing(struct
> > > > mtk_dsi *dsi)
> > > >    		DRM_WARN("HFP + HBP less than d-phy, FPS will
> > > > under
> > > > 60Hz\n");
> > > >    	}
> > > >    
> > > > +	if (dsi->hs_packet_end_aligned) {
> > > 
> > > You can simply check mode_flags here:
> > > 	if (dsi->mode_flags & MIPI_DSI_HS_PKT_END_ALIGNED) {
> > > 
> > > > +		horizontal_sync_active_byte =
> > > > roundup(horizontal_sync_active_byte, dsi->lanes) - 2;
> > > > +		horizontal_frontporch_byte =
> > > > roundup(horizontal_frontporch_byte, dsi->lanes) - 2;
> > > > +		horizontal_backporch_byte =
> > > > roundup(horizontal_backporch_byte, dsi->lanes) - 2;
> > > > +		horizontal_backporch_byte -= (vm->hactive *
> > > > dsi_tmp_buf_bpp + 2) % dsi->lanes;
> > > > +	}
> > > > +
> 
> 
> And if you could add comment explaining the magic here it would be
> nice.
> 
> 
> Regards
> 
> Andrzej
> 
> 
> > > >    	writel(horizontal_sync_active_byte, dsi->regs +
> > > > DSI_HSA_WC);
> > > >    	writel(horizontal_backporch_byte, dsi->regs +
> > > > DSI_HBP_WC);
> > > >    	writel(horizontal_frontporch_byte, dsi->regs +
> > > > DSI_HFP_WC);
> > > > @@ -794,6 +803,9 @@ static int mtk_dsi_host_attach(struct
> > > > mipi_dsi_host *host,
> > > >    	dsi->lanes = device->lanes;
> > > >    	dsi->format = device->format;
> > > >    	dsi->mode_flags = device->mode_flags;
> > > > +	dsi->hs_packet_end_aligned = (dsi->mode_flags &
> > > > +				      MIPI_DSI_HS_PKT_END_ALIGN
> > > > ED)
> > > > +				     ? true : false;
> > > 
> > > ...so there's no need for this one, either.
> > > 
> > > >    
> > > >    	return 0;
> > > >    }
> > > > 
> > > 
> > > Regards,
> > > - Angelo
> > >