linux-kernel - Re: [PATCH v7 5/7] drm: bridge/dw-hdmi: add support for multi byte register width access

Open Source and information security mailing list archives

Date:	Tue, 11 Nov 2014 22:46:39 +0800
From:	Andy Yan <andy.yan@...k-chips.com>
To:	Zubair Lutfullah Kakakhel <Zubair.Kakakhel@...tec.com>,
	airlied@...ux.ie, heiko@...ech.de, fabio.estevam@...escale.com,
	rmk+kernel@....linux.org.uk
CC:	devel@...verdev.osuosl.org, devicetree@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>, Josh Boyer <jwboyer@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	Inki Dae <inki.dae@...sung.com>,
	linux-rockchip@...ts.infradead.org,
	Rob Herring <robh+dt@...nel.org>,
	Sean Paul <seanpaul@...omium.org>, djkurtz@...gle.com,
	Philipp Zabel <p.zabel@...gutronix.de>, ykk@...k-chips.com,
	Grant Likely <grant.likely@...aro.org>,
	Dave Airlie <airlied@...hat.com>,
	Shawn Guo <shawn.guo@...aro.org>, jay.xu@...k-chips.com,
	Lucas Stach <l.stach@...gutronix.de>
Subject: Re: [PATCH v7 5/7] drm: bridge/dw-hdmi: add support for multi byte
 register width access


On 2014年11月11日 22:20, Zubair Lutfullah Kakakhel wrote:
> Hi Andy,
>
> This patch adds the reg-io-width binding.
>
> Hence the binding patch should come before it.
>
    do you mean that I should put dts binding patch
    before this patch?
> 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@...k-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.
   if the dts undefined it, the val will be 1.
   if the dts defined other value except 4 and 1, return -EINVAL
>
> Regards,
> ZubairLK
>    
>
> _______________________________________________
> Linux-rockchip mailing list
> Linux-rockchip@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-rockchip
>
>
>


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