Message-ID: <54621B23.1020602@imgtec.com>
Date: Tue, 11 Nov 2014 14:20:19 +0000
From: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
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To: Andy Yan <andy.yan@rock-chips.com>, <airlied@linux.ie>, <heiko@sntech.de>,
        <fabio.estevam@freescale.com>, <rmk+kernel@arm.linux.org.uk>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Grant Likely <grant.likely@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Shawn Guo <shawn.guo@linaro.org>, Josh Boyer <jwboyer@redhat.com>,
        Sean Paul <seanpaul@chromium.org>, Inki Dae <inki.dae@samsung.com>,
        Dave Airlie <airlied@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
        Lucas Stach <l.stach@pengutronix.de>, <djkurtz@google.com>,
        <ykk@rock-chips.com>, <linux-kernel@vger.kernel.org>,
        <dri-devel@lists.freedesktop.org>, <devel@driverdev.osuosl.org>,
        <devicetree@vger.kernel.org>, <linux-rockchip@lists.infradead.org>,
        <jay.xu@rock-chips.com>
Subject: Re: [PATCH v7 5/7] drm: bridge/dw-hdmi: add support for multi byte
 register width access
References: <1415710229-11935-1-git-send-email-andy.yan@rock-chips.com> <1415710432-12167-1-git-send-email-andy.yan@rock-chips.com>
In-Reply-To: <1415710432-12167-1-git-send-email-andy.yan@rock-chips.com>
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Sender: linux-kernel-owner@vger.kernel.org

Hi Andy,

This patch adds the reg-io-width binding.

Hence the binding patch should come before it.


On 11/11/14 12:53, Andy Yan wrote:
> On rockchip rk3288, only word(32-bit) accesses are
> permitted for hdmi registers.  Byte width accesses (writeb,
> readb) generate an imprecise external abort.
> 
> Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
> 
> ---
> 
>  }
>  
>  static void hdmi_modb(struct dw_hdmi *hdmi, u8 data, u8 mask, unsigned reg)
> @@ -1499,6 +1527,23 @@ static int dw_hdmi_bind(struct device *dev, struct device *master, void *data)
>  	struct device_node *ddc_node;
>  	struct resource *iores;
>  	int ret, irq;
> +	u32 val = 1;
> +
> +	of_property_read_u32(np, "reg-io-width", &val);
> +
> +	switch (val) {
> +	case 4:
> +		hdmi->write = dw_hdmi_writel;
> +		hdmi->read = dw_hdmi_readl;
> +		break;
> +	case 1:
> +		hdmi->write = dw_hdmi_writeb;
> +		hdmi->read = dw_hdmi_readb;
> +		break;
> +	default:
> +		dev_err(dev, "reg-io-width must be 1 or 4\n");
> +		return -EINVAL;
> +	}

The binding patch says this is an optional property.
But here if undefined it returns -EINVAL.

I would keep it optional and default it to byte access.

Regards,
ZubairLK
  
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