[PATCH RFC 3/3] drm/i915/display: Implement fb_mmap callback function

[Das, Nirmoy]

Hi Ville,

On 3/6/2023 3:32 PM, Ville Syrjälä wrote:
> On Mon, Mar 06, 2023 at 11:28:50AM +0100, Nirmoy Das wrote:
>> If stolen memory allocation fails for fbdev, the driver will
>> fallback to system memory. Calculation of smem_start is wrong
>> for such framebuffer objs if the platform comes with no gmadr or
>> no aperture. Solve this by adding fb_mmap callback which also gives
>> driver more control.
>>
>> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_fbdev.c | 20 ++++++++++++++++++++
>>   1 file changed, 20 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
>> index 98ae3a3a986a..ed0f9e2af3ed 100644
>> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
>> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
>> @@ -40,8 +40,10 @@
>>   #include <drm/drm_crtc.h>
>>   #include <drm/drm_fb_helper.h>
>>   #include <drm/drm_fourcc.h>
>> +#include <drm/drm_gem_framebuffer_helper.h>
>>   
>>   #include "gem/i915_gem_lmem.h"
>> +#include "gem/i915_gem_mman.h"
>>   
>>   #include "i915_drv.h"
>>   #include "intel_display_types.h"
>> @@ -120,6 +122,23 @@ static int intel_fbdev_pan_display(struct fb_var_screeninfo *var,
>>   	return ret;
>>   }
>>   
>> +#define to_intel_fbdev(x) container_of(x, struct intel_fbdev, helper)
>> +static int intel_fbdev_mmap(struct fb_info *info, struct vm_area_struct *vma)
>> +{
>> +	struct intel_fbdev *fbdev = to_intel_fbdev(info->par);
>> +	struct drm_gem_object *bo = drm_gem_fb_get_obj(&fbdev->fb->base, 0);
>> +	struct drm_i915_gem_object *obj = to_intel_bo(bo);
>> +	struct drm_device *dev = fbdev->helper.dev;
> You seem to be missing the fb vs. mmio handling here entirely.


Could you please expand this more, I am not so familiar to fbdev code.


>
>> +
>> +	vma->vm_page_prot =
>> +			pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
> Does that do something sane on eg. !PAT?
>
>> +
>> +	if (obj->stolen)
>> +		return vm_iomap_memory(vma, info->fix.smem_start,
>> +				       info->fix.smem_len);
> Why doesn't i915_gem_object_mmap() know how to handle stolen?


Sent out another rfc series to address this.


Regards,

Nirmoy

>
>> +
>> +	return i915_gem_object_mmap(obj, vma);
>> +}
>>   static const struct fb_ops intelfb_ops = {
>>   	.owner = THIS_MODULE,
>>   	DRM_FB_HELPER_DEFAULT_OPS,
>> @@ -131,6 +150,7 @@ static const struct fb_ops intelfb_ops = {
>>   	.fb_imageblit = drm_fb_helper_cfb_imageblit,
>>   	.fb_pan_display = intel_fbdev_pan_display,
>>   	.fb_blank = intel_fbdev_blank,
>> +	.fb_mmap = intel_fbdev_mmap,
>>   };
>>   
>>   static int intelfb_alloc(struct drm_fb_helper *helper,
>> -- 
>> 2.39.0