Subject: [PATCH 1/2] ARM: da850/omap-l138: Add SoC related definitions for VPIF

From: [email-masked] (Sekhar Nori)
Date: Fri, 17 Aug 2012 20:29:12 +0530

Hi Prabhakar,

On 8/16/2012 3:43 PM, Prabhakar Lad wrote:
> On Tuesday 14 August 2012 05:58 PM, Sekhar Nori wrote:

[...]

>>> +int __init da850_register_vpif_display(struct vpif_display_config
>>> +						*display_config)
>>> +{
>>> +	struct resource da850_vpif_display_resource[] = {
>>> +		{
>>> +			.start = IRQ_DA850_VPIFINT,
>>> +			.end   = IRQ_DA850_VPIFINT,
>>> +			.flags = IORESOURCE_IRQ,
>>> +		},
>>> +		{},
>>> +	};
>>> +	unsigned long phys_end_kernel;
>>> +	int ret;
>>> +
>>> +	if (vpif_disp_cont_bufsize) {
>>> +		phys_end_kernel = virt_to_phys((void *)PAGE_OFFSET) +
>>> +					(num_physpages << PAGE_SHIFT);
>>> +		phys_end_kernel += vpif_disp_cont_buf_offset;
>>> +		da850_vpif_display_resource[1].start = phys_end_kernel;
>>> +		da850_vpif_display_resource[1].end = phys_end_kernel +
>>> +						vpif_disp_cont_bufsize - 1;
>>> +		da850_vpif_display_resource[1].flags = IORESOURCE_MEM;
>>> +
>>> +		if (!request_mem_region(da850_vpif_display_resource[1].start,
>>> +				resource_size(&da850_vpif_display_resource[1]),
>>> +				da850_vpif_display_dev.name)) {
>>> +			pr_err("region already claimed.\n");
>>> +			return -EBUSY;
>>> +		}
>>> +		ret = dma_declare_coherent_memory(&da850_vpif_display_dev.dev,
>>> +				phys_end_kernel, phys_end_kernel,
>>> +				vpif_disp_cont_bufsize,
>>> +				DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE);
>>> +
>>> +		if (!ret)
>>> +			return -ENOMEM;
>>> +	}
>>> +	ret = platform_device_add_resources(&da850_vpif_display_dev,
>>> +				da850_vpif_display_resource,
>>> +				ARRAY_SIZE(da850_vpif_display_resource));
>>
>> You are taking memory at the end of RAM and passing it as a IO resource
>> to the driver. This is not correct. For contiguous memory needs can you
>> look at the recently merged CMA framework (include/linux/dma-contiguous.h)
>>
> Ok. But looks like CMA is enabled for CPU_V6/V6K/V7. If CMA is enabled
> for ARM926 too than we can use the global CMA itself rather then doing
> it for each device, then three will be no need to do the above and all
> the kernel parameters can be removed too.

I hadn't followed the CMA development closely so I am not sure of the
reasons behind restricting it to v6+. The patch that added this doesn't
really talk about why it should be restricted to v6+. I am copying Marek
here to see if he can quickly clarify, but may be you can even start a
new thread asking about this.

Thanks,
Sekhar