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
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