Re: [PATCH] da8xx-fb: Rounding FB size to satisfy SGX buffer requirements

[Florian Tobias Schandinat <FlorianSchandinat@gmx.de>]

On 06/12/2012 09:34 AM, Nellutla, Aditya wrote:
> Florian, 
> 
>    I didn't receive any review comments for the patch below. So could you please merge the patch?

As far as I can see there is no feasible alternative so I applied this
patch. If anyone happens to have problems with the larger memory
requirements caused by this, I guess we could make this behavior depend
on a Kconfig symbol.


Best regards,

Florian Tobias Schandinat

> 
> Regards,
> Aditya
> 
> -----Original Message-----
> From: Nellutla, Aditya 
> Sent: Monday, June 04, 2012 11:33 AM
> To: Nellutla, Aditya; linux-fbdev@vger.kernel.org
> Cc: Hiremath, Vaibhav
> Subject: RE: [PATCH] da8xx-fb: Rounding FB size to satisfy SGX buffer requirements
> 
> All, 
>    Did you get chance to review this patch? Request to give your feedback as early as possible.
> 
> Regards,
> Aditya 
> 
> -----Original Message-----
> From: Nellutla, Aditya 
> Sent: Wednesday, May 23, 2012 11:37 AM
> To: linux-fbdev@vger.kernel.org
> Cc: Nellutla, Aditya
> Subject: [PATCH] da8xx-fb: Rounding FB size to satisfy SGX buffer requirements
> 
> In the real time use-case when SGX is used for rendering to FB buffers it has been
> observed that, the available memory from framebuffer driver is not sufficient for
> SGX under certain cases (like 16-bit WVGA resolution). SGX requires 2 swap buffers
> with each of the buffers aligned to lcm(line_length, PAGE_SIZE).
> 
> Inorder to satisfy this requirement, we have two options,
> 
> 	- Increase number of FB buffers (LCD_NUM_BUFFERS) to 3. This is not
> 	  recommended as we end up wasting huge memory in most of the cases.
> 
> 	- Align FB buffers to lcm(line_length, PAGE_SIZE).This ensures framebuffer
> 	  size is increased to satisfy SGX requirements keeping alignment intact.
> 
> This patch makes sure that FB allocates buffers aligned to above formula.
> 
> Signed-off-by: Aditya Nellutla <aditya.n@ti.com>
> ---
>  drivers/video/da8xx-fb.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/video/da8xx-fb.c b/drivers/video/da8xx-fb.c
> index 47118c7..2f24c19 100644
> --- a/drivers/video/da8xx-fb.c
> +++ b/drivers/video/da8xx-fb.c
> @@ -31,6 +31,7 @@
>  #include <linux/cpufreq.h>
>  #include <linux/console.h>
>  #include <linux/slab.h>
> +#include <linux/lcm.h>
>  #include <video/da8xx-fb.h>
>  #include <asm/div64.h>
>  
> @@ -1114,6 +1115,7 @@ static int __devinit fb_probe(struct platform_device *device)
>  	struct da8xx_fb_par *par;
>  	resource_size_t len;
>  	int ret, i;
> +	unsigned long ulcm;
>  
>  	if (fb_pdata = NULL) {
>  		dev_err(&device->dev, "Can not get platform data\n");
> @@ -1209,7 +1211,8 @@ static int __devinit fb_probe(struct platform_device *device)
>  
>  	/* allocate frame buffer */
>  	par->vram_size = lcdc_info->width * lcdc_info->height * lcd_cfg->bpp;
> -	par->vram_size = PAGE_ALIGN(par->vram_size/8);
> +	ulcm = lcm((lcdc_info->width * lcd_cfg->bpp)/8, PAGE_SIZE);
> +	par->vram_size = roundup(par->vram_size/8, ulcm);
>  	par->vram_size = par->vram_size * LCD_NUM_BUFFERS;
>  
>  	par->vram_virt = dma_alloc_coherent(NULL,