On Mon, Apr 18, 2011 at 10:03:06PM +0100, Alan Cox wrote:
> So has this been benchmarked - intuitively I'd agree and expect that a
> shadowfb driver ought to give best performance.
No, but it's noticably nicer to use under virt-manager. I'll try to come
up with some numbers.
> > +/* Map the framebuffer from the card and configure the core */
> > +static int cirrus_vram_init(struct cirrus_device *cdev)
> > +{
> > + int ret;
> > +
> > + /* BAR 0 is VRAM */
> > + cdev->mc.vram_base = pci_resource_start(cdev->ddev->pdev, 0);
> > + /* We have 4MB of VRAM */
> > + cdev->mc.vram_size = 4 * 1024 * 1024;
>
> For real hardware at least you should check that the pci resource is at
> least 4Mb long before doing this, otherwise the resulting progression in
> the fail case is that you map some other device into user address space,
> which isn't good!
True. The PCI table is restrictive enough that it won't bind to real
hardware, so I don't know if it's worth it to be paranoid.
> > +static void cirrus_encoder_mode_set(struct drm_encoder *encoder,
> > + struct drm_display_mode *mode,
> > + struct drm_display_mode *adjusted_mode)
> > +{
> > + struct drm_device *dev = encoder->dev;
> > + struct cirrus_device *cdev = dev->dev_private;
> > +
> > + unsigned char tmp;
> > +
> > + switch (encoder->crtc->fb->bits_per_pixel) {
> > + case 8:
> > + tmp = 0x0;
> > + break;
> > + case 16:
> > + /* Enable 16 bit mode */
> > + WREG_HDR(0x01);
>
> If you switch back from 16 does this not need clearing ?
Nope. qemu just looks at this to distinguish between 15 and 16 bit, and
I've no intention of supporting 15 bit...
--
Matthew Garrett | mjg59@xxxxxxxxxxxxx
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