linux-kernel - Re: [RFC 2/3] drm/mediatek: add support for Mediatek SoC MT2701

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Date:	Wed, 18 May 2016 21:26:04 +0100
From:	Emil Velikov <emil.l.velikov@...il.com>
To:	YT Shen <yt.shen@...iatek.com>
Cc:	Philipp Zabel <p.zabel@...gutronix.de>,
	ML dri-devel <dri-devel@...ts.freedesktop.org>,
	Mark Rutland <mark.rutland@....com>,
	devicetree <devicetree@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>,
	srv_heupstream@...iatek.com, Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	Mao Huang <littlecvr@...omium.org>,
	Rob Herring <robh+dt@...nel.org>,
	linux-mediatek@...ts.infradead.org,
	Kumar Gala <galak@...eaurora.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Sascha Hauer <kernel@...gutronix.de>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC 2/3] drm/mediatek: add support for Mediatek SoC MT2701

On 18 May 2016 at 09:33, YT Shen <yt.shen@...iatek.com> wrote:

>> > @@ -108,6 +108,10 @@ int mtk_drm_gem_dumb_create(struct drm_file *file_priv, struct drm_device *dev,
>> >         int ret;
>> >
>> >         args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
>> > +       /*
>> > +       * align to 8 bytes since Mali requires it.
>> > +       */
>> > +       args->pitch = ALIGN(args->pitch, 8);
>> Are you sure we need this, based on the line just above ?
> I think bpp stands for bits per pixel, so width * bpp / 8 simply transfer from bits to bytes, which
> cannot guarantee align to 8.
>
You're absolutely correct. Reading the comment made me loose my mind
and completely misinterpret the division macro.

> I will remove this align part from the patch, this constraint is not from display controller.
Thank you !

Regards
Emil