linux-kernel - Re: [PATCH 19/28] gpu/drm: remove the powerpc hack in drm_legacy_sg

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Date:   Wed, 8 Apr 2020 14:25:04 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Christoph Hellwig <hch@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, x86@...nel.org,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Laura Abbott <labbott@...hat.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Minchan Kim <minchan@...nel.org>,
        Nitin Gupta <ngupta@...are.org>,
        Robin Murphy <robin.murphy@....com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Peter Zijlstra <peterz@...radead.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-hyperv@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 19/28] gpu/drm: remove the powerpc hack in
 drm_legacy_sg_alloc

On Wed, Apr 08, 2020 at 01:59:17PM +0200, Christoph Hellwig wrote:
> If this code was broken for non-coherent caches a crude powerpc hack
> isn't going to help anyone else.  Remove the hack as it is the last
> user of __vmalloc passing a page protection flag other than PAGE_KERNEL.

Well Ben added this to make stuff work on ppc, ofc the home grown dma
layer in drm from back then isn't going to work in other places. I guess
should have at least an ack from him, in case anyone still cares about
this on ppc. Adding Ben to cc.
-Daniel

> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  drivers/gpu/drm/drm_scatter.c | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_scatter.c b/drivers/gpu/drm/drm_scatter.c
> index ca520028b2cb..f4e6184d1877 100644
> --- a/drivers/gpu/drm/drm_scatter.c
> +++ b/drivers/gpu/drm/drm_scatter.c
> @@ -43,15 +43,6 @@
>  
>  #define DEBUG_SCATTER 0
>  
> -static inline void *drm_vmalloc_dma(unsigned long size)
> -{
> -#if defined(__powerpc__) && defined(CONFIG_NOT_COHERENT_CACHE)
> -	return __vmalloc(size, GFP_KERNEL, pgprot_noncached_wc(PAGE_KERNEL));
> -#else
> -	return vmalloc_32(size);
> -#endif
> -}
> -
>  static void drm_sg_cleanup(struct drm_sg_mem * entry)
>  {
>  	struct page *page;
> @@ -126,7 +117,7 @@ int drm_legacy_sg_alloc(struct drm_device *dev, void *data,
>  		return -ENOMEM;
>  	}
>  
> -	entry->virtual = drm_vmalloc_dma(pages << PAGE_SHIFT);
> +	entry->virtual = vmalloc_32(pages << PAGE_SHIFT);
>  	if (!entry->virtual) {
>  		kfree(entry->busaddr);
>  		kfree(entry->pagelist);
> -- 
> 2.25.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch