linux-kernel - Re: [PATCH v3] drm/bridge/synopsys: dsi: add optional pixel clock

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Message-ID: <507552a3-c68f-d6ac-a747-b8f5168d0d41@st.com>
Date:   Wed, 24 Jan 2018 09:24:06 +0000
From:   Philippe CORNU <philippe.cornu@...com>
To:     Brian Norris <briannorris@...omium.org>
CC:     Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Bhumika Goyal <bhumirks@...il.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sandy Huang <hjc@...k-chips.com>,
        Heiko Stubner <heiko@...ech.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-rockchip@...ts.infradead.org" 
        <linux-rockchip@...ts.infradead.org>,
        Yannick FERTRE <yannick.fertre@...com>,
        Vincent ABRIOU <vincent.abriou@...com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Ludovic BARRE <ludovic.barre@...com>,
        Mickael REULIER <mickael.reulier@...com>,
        "hl@...k-chips.com" <hl@...k-chips.com>,
        "Chris Zhong" <zyw@...k-chips.com>,
        "nickey.yang@...k-chips.com" <nickey.yang@...k-chips.com>
Subject: Re: [PATCH v3] drm/bridge/synopsys: dsi: add optional pixel clock

Hi Brian,


On 01/23/2018 09:49 PM, Brian Norris wrote:
> Hi,
> 
> Philippe asked me to review the last version. I'm not sure I have a lot
> to contribute. Maybe Rockchip folks who wrote this stuff in the first
> place might. I've CC'd some.
> 
> On Tue, Jan 23, 2018 at 06:08:06PM +0100, Philippe Cornu wrote:
>> The pixel clock is optional. When available, it offers a better
>> preciseness for timing computations and allows to reduce the extra dsi
>> bandwidth in burst mode (from ~20% to ~10-12%, hw platform dependant).
>>
>> Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
>> Signed-off-by: Philippe Cornu <philippe.cornu@...com>
>> ---
>> Changes in v3: Simplify px_clk probing thanks to Andrzej Hajda comments
>>
>> Changes in v2: Improve px_clk probing in case of ENOENT dt returned value
>> (thanks to Philipp Zabel & Andrzej Hajda comments)
>>
>>   drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 25 +++++++++++++++++++------
>>   1 file changed, 19 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> index ed8af32f8e52..9fb35385c348 100644
>> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> @@ -217,6 +217,7 @@ struct dw_mipi_dsi {
>>   	void __iomem *base;
>>   
>>   	struct clk *pclk;
>> +	struct clk *px_clk;
>>   
>>   	unsigned int lane_mbps; /* per lane */
>>   	u32 channel;
>> @@ -703,24 +704,28 @@ static void dw_mipi_dsi_bridge_mode_set(struct drm_bridge *bridge,
>>   	struct dw_mipi_dsi *dsi = bridge_to_dsi(bridge);
>>   	const struct dw_mipi_dsi_phy_ops *phy_ops = dsi->plat_data->phy_ops;
>>   	void *priv_data = dsi->plat_data->priv_data;
>> +	struct drm_display_mode px_clk_mode = *mode;
>>   	int ret;
>>   
>>   	clk_prepare_enable(dsi->pclk);
>>   
>> -	ret = phy_ops->get_lane_mbps(priv_data, mode, dsi->mode_flags,
>> +	if (dsi->px_clk)
>> +		px_clk_mode.clock = clk_get_rate(dsi->px_clk) / 1000;
>> +
>> +	ret = phy_ops->get_lane_mbps(priv_data, &px_clk_mode, dsi->mode_flags,
>>   				     dsi->lanes, dsi->format, &dsi->lane_mbps);
>>   	if (ret)
>>   		DRM_DEBUG_DRIVER("Phy get_lane_mbps() failed\n");
>>   
>>   	pm_runtime_get_sync(dsi->dev);
>>   	dw_mipi_dsi_init(dsi);
>> -	dw_mipi_dsi_dpi_config(dsi, mode);
>> +	dw_mipi_dsi_dpi_config(dsi, &px_clk_mode);
>>   	dw_mipi_dsi_packet_handler_config(dsi);
>>   	dw_mipi_dsi_video_mode_config(dsi);
>> -	dw_mipi_dsi_video_packet_config(dsi, mode);
>> +	dw_mipi_dsi_video_packet_config(dsi, &px_clk_mode);
>>   	dw_mipi_dsi_command_mode_config(dsi);
>> -	dw_mipi_dsi_line_timer_config(dsi, mode);
>> -	dw_mipi_dsi_vertical_timing_config(dsi, mode);
>> +	dw_mipi_dsi_line_timer_config(dsi, &px_clk_mode);
>> +	dw_mipi_dsi_vertical_timing_config(dsi, &px_clk_mode);
>>   
>>   	dw_mipi_dsi_dphy_init(dsi);
>>   	dw_mipi_dsi_dphy_timing_config(dsi);
>> @@ -734,7 +739,7 @@ static void dw_mipi_dsi_bridge_mode_set(struct drm_bridge *bridge,
>>   
>>   	dw_mipi_dsi_dphy_enable(dsi);
>>   
>> -	dw_mipi_dsi_wait_for_two_frames(mode);
>> +	dw_mipi_dsi_wait_for_two_frames(&px_clk_mode);
>>   
>>   	/* Switch to cmd mode for panel-bridge pre_enable & panel prepare */
>>   	dw_mipi_dsi_set_mode(dsi, 0);
>> @@ -828,6 +833,14 @@ __dw_mipi_dsi_probe(struct platform_device *pdev,
>>   		return ERR_PTR(ret);
>>   	}
>>   
>> +	dsi->px_clk = devm_clk_get(dev, "px_clk");
> 
> Did you write a device tree binding document update for this anywhere?
> 
> Brian
> 

Many thanks for your review,

yes, "px_clk" is already documented, please have a look to 
Documentation/devicetree/bindings/display/bridge/dw_mipi_dsi.txt

Philippe :-)

>> +	if (IS_ERR(dsi->px_clk)) {
>> +		ret = PTR_ERR(dsi->px_clk);
>> +		if (ret != ENOENT)
>> +			dev_err(dev, "Unable to get opt. px_clk: %d\n", ret);
>> +		dsi->px_clk = NULL;
>> +	}
>> +
>>   	/*
>>   	 * Note that the reset was not defined in the initial device tree, so
>>   	 * we have to be prepared for it not being found.
>> -- 
>> 2.15.1
>>