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

[Prabhakar Lad]

Hi Marek,

On Fri, Aug 17, 2012 at 8:39 PM, Marek Szyprowski
<m.szyprowski at samsung.com> wrote:
> Hello,
>
> On Friday, August 17, 2012 4:59 PM Sekhar Nori wrote:
>
>> 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.
>
> Frankly, this is a leftover from some earlier suggestions that CMA should solve the
> aliasing of coherent mappings, which might be a problem on v6+. If it works correctly
> on pre-v6, then this dependency should be removed. Feel free to submit a patch and
> I will take it to my fixes branch.
>

I have created a patch for enabling CMA on CPU32_v5 [1], and also
tested it works.
Soon posting this patch.

[1] http://git.linuxtv.org/mhadli/v4l-dvb-davinci_devices.git/commitdiff/e940a1b9262bde96eec4b18971a6307f24262667?hp=2f30ae4ee373fe4c69ab1606373538dcc99ed283

Thanks and Regards,
--Prabhakar Lad

> Best regards
> --
> Marek Szyprowski
> Samsung Poland R&D Center
>
>
>
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