linux-kernel - Re: [PATCH v9 3/5] drm/sun4i: sun6i_mipi_dsi: Support vblk timing for 4-lane devices

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Message-ID: <20190311140402.ie7abxda6pizrybj@flea>
Date:   Mon, 11 Mar 2019 15:04:02 +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 <dri-devel@...ts.freedesktop.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-amarula@...rulasolutions.com,
        Michael Trimarchi <michael@...rulasolutions.com>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH v9 3/5] drm/sun4i: sun6i_mipi_dsi: Support vblk timing
 for 4-lane devices

On Thu, Mar 07, 2019 at 09:33:38PM +0530, Jagan Teki wrote:
> On Mon, Mar 4, 2019 at 9:19 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
> >
> > On Sun, Mar 03, 2019 at 11:05:25PM +0530, Jagan Teki wrote:
> > > Like other dsi setup timings, or hblk for that matter vblk would
> > > also require compute the timings based payload equation along with
> > > packet overhead.
> > >
> > > But, on the other hand vblk computation is also depends on device
> > > lane number.
> > > - for 4 lane devices, it is computed based on vtotal, packet overhead
> > >   along with hblk value.
> > > - for others devices, it is simply 0
> > >
> > > BSP code from BPI-M64-bsp is computing vblk as for 4-lane devices
> > > (from linux-sunxi
> > > drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)
> > >
> > > tmp = (ht*dsi_pixel_bits[format]/8)*vt-(4+dsi_hblk+2);
> > > dsi_vblk = (lane-tmp%lane);
> > >
> > > So, update the vblk timing calculation to support all type of
> > > devices.
> > >
> > > Tested on 2-lane, 4-lane MIPI-DSI LCD panels.
> >
> > You should be explaining which issue you faced, in which setup, what
> > were its symptoms and how that solution is fixing it.
> 
> No, it is not a fix, didn't specify either. it is vblk timings support
> like others dsi timings.

So it's not fixing anything, and this isn't a new feature
either. What's the point then?

Maxime

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

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