linux-kernel - Re: [PATCH v5 04/12] drm: renesas: rz-du: mipi

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Message-ID: <20250520140514.GD13321@pendragon.ideasonboard.com>
Date: Tue, 20 May 2025 16:05:14 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Biju Das <biju.das.jz@...renesas.com>, David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Magnus Damm <magnus.damm@...il.com>,
	dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v5 04/12] drm: renesas: rz-du: mipi_dsi: Simplify HSFREQ
 calculation

Hi Prabhakar,

Thank you for the patch.

On Mon, May 12, 2025 at 07:23:22PM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> 
> Simplify the high-speed clock frequency (HSFREQ) calculation by removing
> the redundant multiplication and division by 8. The updated equation:
> 
>     hsfreq = (mode->clock * bpp) / (dsi->lanes);

You can drop the parentheses around the second factor. You can actuall
drop all prentheses.

> 
> produces the same result while improving readability and clarity.
> 
> Additionally, update the comment to clarify the relationship between HS
> clock bit frequency, HS byte clock frequency, and HSFREQ.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> Reviewed-by: Biju Das <biju.das.jz@...renesas.com>
> ---
> v4->v5:
> - No changes
> 
> v3->v4:
> - No changes
> 
> v2->v3:
> - No changes
> 
> v1->v2:
> - Added Reviewed-by tag from Biju
> ---
>  drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> index ec8baecb9ba5..c5f698cd74f1 100644
> --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> @@ -277,10 +277,10 @@ static int rzg2l_mipi_dsi_startup(struct rzg2l_mipi_dsi *dsi,
>  	 *       hsclk: DSI HS Byte clock frequency (Hz)
>  	 *       lanes: number of data lanes
>  	 *
> -	 * hsclk(bit) = hsclk(byte) * 8
> +	 * hsclk(bit) = hsclk(byte) * 8 = hsfreq
>  	 */
>  	bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
> -	hsfreq = (mode->clock * bpp * 8) / (8 * dsi->lanes);
> +	hsfreq = (mode->clock * bpp) / dsi->lanes;

You can drop the parentheses here too.

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

>  
>  	ret = pm_runtime_resume_and_get(dsi->dev);
>  	if (ret < 0)

-- 
Regards,

Laurent Pinchart