linux-kernel - Re: [PATCH v9 5/5] drm/sun4i: sun6i_mipi_dsi: Simplify dsi setup timings code

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Date:   Mon, 4 Mar 2019 16:50:14 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Jagan Teki <jagan@...rulasolutions.com>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Chen-Yu Tsai <wens@...e.org>, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-amarula@...rulasolutions.com,
        Michael Trimarchi <michael@...rulasolutions.com>,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH v9 5/5] drm/sun4i: sun6i_mipi_dsi: Simplify dsi setup
 timings code

On Sun, Mar 03, 2019 at 11:05:27PM +0530, Jagan Teki wrote:
> DSI timings are varies between burst/non-burst devices and
> current driver is handling this support via if, else statements
> which would difficult to read.
> 
> Simplify it by using goto to make code more readable.
> 
> Signed-off-by: Jagan Teki <jagan@...rulasolutions.com>
> Tested-by: Merlijn Wajer <merlijn@...zup.org>
> ---
> Note: This change is created based on previous version burst
> changes [1] by addressing comment from [2] by Maxime to make
> code readable. 
> 
> [1] https://patchwork.kernel.org/cover/10813623/
> [2] https://patchwork.kernel.org/patch/10666607/
> 
>  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 79 ++++++++++++++------------
>  1 file changed, 42 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 31ec4048804d..898f32319c2d 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -550,7 +550,8 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
>  {
>  	struct mipi_dsi_device *device = dsi->device;
>  	unsigned int Bpp = mipi_dsi_pixel_format_to_bpp(device->format) / 8;
> -	u16 hbp = 0, hfp = 0, hsa = 0, hblk = 0, vblk = 0;
> +	u16 hbp, hfp, hsa, hblk;
> +	u16 vblk = 0;
>  	u32 basic_ctl = 0;
>  	size_t bytes;
>  	u8 *buffer;
> @@ -558,6 +559,7 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
>  	/* Do all timing calculations up front to allocate buffer space */
>  
>  	if (device->mode_flags & MIPI_DSI_MODE_VIDEO_BURST) {
> +		hbp = hfp = hsa = 0;

This raises a checkpatch warning and isn't necessary

>  		hblk = mode->hdisplay * Bpp;
>  		basic_ctl = SUN6I_DSI_BASIC_CTL_VIDEO_BURST |
>  			    SUN6I_DSI_BASIC_CTL_HSA_HSE_DIS |
> @@ -566,48 +568,51 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
>  		if (device->lanes == 4)
>  			basic_ctl |= SUN6I_DSI_BASIC_CTL_TRAIL_FILL |
>  				     SUN6I_DSI_BASIC_CTL_TRAIL_INV(0xc);
> -	} else {
> -		/*
> -		 * A sync period is composed of a blanking packet (4
> -		 * bytes + payload + 2 bytes) and a sync event packet
> -		 * (4 bytes). Its minimal size is therefore 10 bytes
> -		 */
> +
> +		goto alloc_buf;

And I'd rather not have a goto in the middle of the code for no
particular reason.

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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