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From:   Paul Boddie <paul@boddie.org.uk>
To:     dri-devel@lists.freedesktop.org
Cc:     Paul Cercueil <paul@crapouillou.net>,
        Emil Velikov <emil.l.velikov@gmail.com>,
        devicetree <devicetree@vger.kernel.org>, od@zcrc.me,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        David Airlie <airlied@linux.ie>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org, Rob Herring <robh+dt@kernel.org>
Subject: Re: [PATCH 11/12] gpu/drm: Ingenic: Add support for the IPU
Date:   Tue, 19 May 2020 19:10:32 +0200
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On Monday 18. May 2020 13.26.58 Paul Cercueil wrote:
> >>  
> >>  @@ -186,13 +186,16 @@ static void
> >> 
> >> ingenic_drm_crtc_update_timings(struct ingenic_drm *priv,
> >> 
> >>          regmap_update_bits(priv->map, JZ_REG_LCD_CTRL,
> >>                             JZ_LCD_CTRL_OFUP | JZ_LCD_CTRL_BURST_16,
> >>                             JZ_LCD_CTRL_OFUP | JZ_LCD_CTRL_BURST_16);
> >>  
> >>  +
> >>  +       regmap_write(priv->map, JZ_REG_LCD_IPUR, JZ_LCD_IPUR_IPUREN
> >>  +                    (ht * vpe / 3) << JZ_LCD_IPUR_IPUR_LSB);
> > 
> > This hunk also indicates that it may be better to merge the IPU within
> > the existing driver.
> 
> This writes the IPUR register of the CRTC, nothing wrong here.

Since I noticed it in the above patch details, I think the mask when updating 
the burst setting in the LCD_CTRL register should - in general - involve 
multiple bits, since the BST field is 3 bits wide on the JZ4780 and 2 bits 
wide on earlier products. Just setting BURST_16 (0b10) could potentially 
enable BURST_32 (0b11) or other field values that are not explicitly defined.

Hope this is useful!

Paul