linux-kernel - Re: [PATCH v15 08/19] drm/etnaviv: Fix wrong caching mode being used for non writecombine buffers

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Message-ID: <006d7bacd2df40b9d6bc8d36836a6c1dd6dfb939.camel@pengutronix.de>
Date: Tue, 01 Oct 2024 15:58:59 +0200
From: Lucas Stach <l.stach@...gutronix.de>
To: Sui Jingfeng <sui.jingfeng@...ux.dev>
Cc: Christian Gmeiner <christian.gmeiner@...il.com>, Russell King
	 <linux+etnaviv@...linux.org.uk>, dri-devel@...ts.freedesktop.org, 
	etnaviv@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v15 08/19] drm/etnaviv: Fix wrong caching mode being
 used for non writecombine buffers

Am Sonntag, dem 08.09.2024 um 17:43 +0800 schrieb Sui Jingfeng:
> In the etnaviv_gem_vmap_impl() function, the driver vmap whatever buffers
> with write combine(WC) page property. This is incorrect, as some platforms
> are cached coherent. Cached buffers should be mapped with cached page
> property.
> 
> Fixes: a0a5ab3e99b8 ("drm/etnaviv: call correct function when trying to vmap a DMABUF")
> Signed-off-by: Sui Jingfeng <sui.jingfeng@...ux.dev>
> ---
>  drivers/gpu/drm/etnaviv/etnaviv_gem.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> index 1fd2cff20ef4..b899aea64e22 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> @@ -393,6 +393,7 @@ static void etnaviv_gem_object_vunmap(struct drm_gem_object *obj,
>  static void *etnaviv_gem_vmap_impl(struct etnaviv_gem_object *obj)
>  {
>  	struct page **pages;
> +	pgprot_t prot;
>  
>  	lockdep_assert_held(&obj->lock);
>  
> @@ -400,8 +401,19 @@ static void *etnaviv_gem_vmap_impl(struct etnaviv_gem_object *obj)
>  	if (IS_ERR(pages))
>  		return NULL;
>  
> -	return vmap(pages, obj->base.size >> PAGE_SHIFT,
> -			VM_MAP, pgprot_writecombine(PAGE_KERNEL));
> +	switch (obj->flags) {

obj->flags & ETNA_BO_CACHE_MASK

> +	case ETNA_BO_CACHED:
> +		prot = PAGE_KERNEL;
> +		break;
> +	case ETNA_BO_UNCACHED:
> +		prot = pgprot_noncached(PAGE_KERNEL);
> +		break;
> +	case ETNA_BO_WC:
> +	default:
> +		prot = pgprot_writecombine(PAGE_KERNEL);
> +	}
> +
> +	return vmap(pages, obj->base.size >> PAGE_SHIFT, VM_MAP, prot);
>  }
>  
>  static inline enum dma_data_direction etnaviv_op_to_dma_dir(u32 op)