by Sekhar Nori

[permalink] [raw]

Subject: RE: [PATCH v4 08/11] tty: add pruss SUART driver

On Mon, May 16, 2011 at 10:47:18, Subhasish Ghosh wrote:
> Hi Sekhar,
>
> >>> Say, if the driver is loaded as a module.
> >>> If I allocate the sram in the platform code, how to I
> >>> free it when the driver is unloaded.
> >>
> >> This is what I said in my last e-mail. What is
> >> the issue you see with this approach?
> >>
> >> | Thanks for the clarification. In this case, the driver
> >> | should use platform callbacks to get/put fast fifo
> >> | space. In case this callback is not populated by the
> >> | platform or returns an error, the driver should fall
> >> | back to allocating from DDR.
> >>
> >
> > ok, so what you are suggesting is that I implement some
> > callbacks (like .fifo_alloc, .fifo_dealloc) which can allocate
> > memory using sram_alloc.
> > My doubt is, if already such API's are there (by Russel) or you
> > are suggesting to implement them.
>
> I can add the fifo_alloc/dealloc as part of the suart platform_data,
> Is that's what you are suggesting. If you may please point me out
> to any example. I am just not clear with this.

Yes, that's what I am suggesting. I don't have an exact example
for you, but for an example of how function pointers can be passed
along in platform data you can look at the platform data for
DA8x FB driver in include/video/da8xx-fb.h.

Hope that helps.

Thanks,
Sekhar

2011-05-20 07:13:30

by Subhasish Ghosh

[permalink] [raw]

Subject: Re: [PATCH v4 08/11] tty: add pruss SUART driver

Hi Sekhar,

>> > ok, so what you are suggesting is that I implement some
>> > callbacks (like .fifo_alloc, .fifo_dealloc) which can allocate
>> > memory using sram_alloc.
>> > My doubt is, if already such API's are there (by Russel) or you
>> > are suggesting to implement them.
>>
>> I can add the fifo_alloc/dealloc as part of the suart platform_data,
>> Is that's what you are suggesting. If you may please point me out
>> to any example. I am just not clear with this.
>
> Yes, that's what I am suggesting. I don't have an exact example
> for you, but for an example of how function pointers can be passed
> along in platform data you can look at the platform data for
> DA8x FB driver in include/video/da8xx-fb.h.
>

Does this look ok.
This code snippet is in the driver file.

if (soft_uart->use_sram) {
soft_uart->suart_iomap.p_fifo_buff_virt_base =
pdata->fifo_alloc(SUART_CNTX_SZ * NR_SUART * 2,
(dma_addr_t *)
&soft_uart->suart_iomap.p_fifo_buff_phys_base);
if (!soft_uart->suart_iomap.p_fifo_buff_virt_base) {
soft_uart->suart_iomap.p_fifo_buff_virt_base =
dma_alloc_coherent(&pdev->dev,
SUART_CNTX_SZ * NR_SUART * 2,
(dma_addr_t *) &soft_uart->suart_iomap.
p_fifo_buff_phys_base, GFP_KERNEL);
soft_uart->use_sram = false;
if (!soft_uart->suart_iomap.p_fifo_buff_virt_base)
goto probe_exit_iounmap;
}
} else {
soft_uart->suart_iomap.p_fifo_buff_virt_base =
dma_alloc_coherent(&pdev->dev,
SUART_CNTX_SZ * NR_SUART * 2,
(dma_addr_t *) &soft_uart->suart_iomap.
p_fifo_buff_phys_base, GFP_KERNEL);
if (!soft_uart->suart_iomap.p_fifo_buff_virt_base)
goto probe_exit_iounmap;
}

I added the fifo_alloc into the suart_data of the board file.

static struct da850_evm_pruss_suart_data suart_data = {
.version = 1,
.setup = da850_evm_pruss_suart_setup,
.fifo_alloc = sram_alloc,
.fifo_free = sram_free,
};

Best Regards,
Subhasish Ghosh