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

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Date:   Fri, 14 Jan 2022 12:11:38 +0100
From:   Andrzej Hajda <andrzej.hajda@...el.com>
To:     Rex-BC Chen <rex-bc.chen@...iatek.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


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_ALIGNED)
>>> +				     ? true : false;
>> ...so there's no need for this one, either.
>>
>>>    
>>>    	return 0;
>>>    }
>>>
>> Regards,
>> - Angelo
>>