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

Zubair Lutfullah Kakakhel
2014-11-11T14:37:59Z

On 11/11/14 14:23, Lucas Stach wrote:
> Am Dienstag, den 11.11.2014, 14:20 +0000 schrieb Zubair Lutfullah
> Kakakhel:
>> 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.
>
> That's exactly what the patch does. val is initialized to 1, which is
> not changed if the property could not be found in the DT. The default
> case will only be taken if the property is present in DT but has any
> other value than 1 or 4, which is an error.
>

I missed the initialization. My bad.

Thanks
ZubairLK