Re: [Intel-gfx] [PATCH 06/13] drm: add helper to clflush a virtual address range

Ben Widawsky
2011-11-21T19:46:49Z

On Sun, Nov 06, 2011 at 08:13:53PM +0100, Daniel Vetter wrote:
> Useful when the page is already mapped to copy date in/out.
>
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
> drivers/gpu/drm/drm_cache.c | 23 +++++++++++++++++++++++
> include/drm/drmP.h | 1 +
> 2 files changed, 24 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c
> index 0e3bd5b..502771a 100644
> --- a/drivers/gpu/drm/drm_cache.c
> +++ b/drivers/gpu/drm/drm_cache.c
> @@ -97,3 +97,26 @@ drm_clflush_pages(struct page *pages[], unsigned long num_pages)
> #endif
> }
> EXPORT_SYMBOL(drm_clflush_pages);
> +
> +void
> +drm_clflush_virt_range(char *addr, unsigned long length)
> +{
> +#if defined(CONFIG_X86)
> + if (cpu_has_clflush) {
> + char *end = addr + length;
> + mb();
> + for (; addr < end; addr += boot_cpu_data.x86_clflush_size)
> + clflush(addr);
> + clflush(end - 1);
> + mb();
> + return;
> + }
> +
> + if (on_each_cpu(drm_clflush_ipi_handler, NULL, 1) != 0)
> + printk(KERN_ERR "Timed out waiting for cache flush.\n");
> +#else
> + printk(KERN_ERR "Architecture has no drm_cache.c support\n");
> + WARN_ON_ONCE(1);
> +#endif
> +}
> +EXPORT_SYMBOL(drm_clflush_virt_range);

I'd feel more comfortable with a BUG_ON(irqs_disabled()); before the
IPI... though I don't even know how many platforms that actually
pertains to (if any).