linux-kernel - Re: [PATCH 1/3] drm/msm: add MSM_BO_CACHED

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Message-ID: <20201001234758.GH29832@jcrouse1-lnx.qualcomm.com>
Date:   Thu, 1 Oct 2020 17:47:58 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     Jonathan Marek <jonathan@...ek.ca>
Cc:     freedreno@...ts.freedesktop.org, Rob Clark <robdclark@...il.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Shawn Guo <shawn.guo@...aro.org>,
        AngeloGioacchino Del Regno <kholk11@...il.com>,
        Sharat Masetty <smasetty@...eaurora.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] drm/msm: add MSM_BO_CACHED_COHERENT

On Wed, Sep 30, 2020 at 08:27:04PM -0400, Jonathan Marek wrote:
> Add a new cache mode for creating coherent host-cached BOs.

Reviewed-by: Jordan Crouse <jcrouse@...eaurora.org>

> Signed-off-by: Jonathan Marek <jonathan@...ek.ca>
> ---
>  drivers/gpu/drm/msm/adreno/adreno_device.c | 1 +
>  drivers/gpu/drm/msm/msm_drv.h              | 1 +
>  drivers/gpu/drm/msm/msm_gem.c              | 8 ++++++++
>  include/uapi/drm/msm_drm.h                 | 5 ++---
>  4 files changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c
> index 9eeb46bf2a5d..2aa707546254 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_device.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
> @@ -410,6 +410,7 @@ static int adreno_bind(struct device *dev, struct device *master, void *data)
>  		config.rev.minor, config.rev.patchid);
>  
>  	priv->is_a2xx = config.rev.core == 2;
> +	priv->has_cached_coherent = config.rev.core >= 6;
>  
>  	gpu = info->init(drm);
>  	if (IS_ERR(gpu)) {
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index 2c3225bc1794..6384844b1696 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -167,6 +167,7 @@ struct msm_drm_private {
>  	struct msm_file_private *lastctx;
>  	/* gpu is only set on open(), but we need this info earlier */
>  	bool is_a2xx;
> +	bool has_cached_coherent;
>  
>  	struct drm_fb_helper *fbdev;
>  
> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
> index b2f49152b4d4..ad9a627493ae 100644
> --- a/drivers/gpu/drm/msm/msm_gem.c
> +++ b/drivers/gpu/drm/msm/msm_gem.c
> @@ -431,6 +431,9 @@ static int msm_gem_pin_iova(struct drm_gem_object *obj,
>  	if (msm_obj->flags & MSM_BO_MAP_PRIV)
>  		prot |= IOMMU_PRIV;
>  
> +	if (msm_obj->flags & MSM_BO_CACHED_COHERENT)
> +		prot |= IOMMU_CACHE;
> +
>  	WARN_ON(!mutex_is_locked(&msm_obj->lock));
>  
>  	if (WARN_ON(msm_obj->madv != MSM_MADV_WILLNEED))
> @@ -998,6 +1001,7 @@ static int msm_gem_new_impl(struct drm_device *dev,
>  		uint32_t size, uint32_t flags,
>  		struct drm_gem_object **obj)
>  {
> +	struct msm_drm_private *priv = dev->dev_private;
>  	struct msm_gem_object *msm_obj;
>  
>  	switch (flags & MSM_BO_CACHE_MASK) {
> @@ -1005,6 +1009,10 @@ static int msm_gem_new_impl(struct drm_device *dev,
>  	case MSM_BO_CACHED:
>  	case MSM_BO_WC:
>  		break;
> +	case MSM_BO_CACHED_COHERENT:
> +		if (priv->has_cached_coherent)
> +			break;
> +		/* fallthrough */

It confused me that this kind of implicitly fell into the else clause in
msm_gem_mmap_obj, but I'm on board. This is a good solution since it only allows
I/O coherence with caching.

>  	default:
>  		DRM_DEV_ERROR(dev->dev, "invalid cache flag: %x\n",
>  				(flags & MSM_BO_CACHE_MASK));
> diff --git a/include/uapi/drm/msm_drm.h b/include/uapi/drm/msm_drm.h
> index a6c1f3eb2623..474497e8743a 100644
> --- a/include/uapi/drm/msm_drm.h
> +++ b/include/uapi/drm/msm_drm.h
> @@ -94,12 +94,11 @@ struct drm_msm_param {
>  #define MSM_BO_CACHED        0x00010000
>  #define MSM_BO_WC            0x00020000
>  #define MSM_BO_UNCACHED      0x00040000
> +#define MSM_BO_CACHED_COHERENT 0x080000
>  
>  #define MSM_BO_FLAGS         (MSM_BO_SCANOUT | \
>                                MSM_BO_GPU_READONLY | \
> -                              MSM_BO_CACHED | \
> -                              MSM_BO_WC | \
> -                              MSM_BO_UNCACHED)
> +                              MSM_BO_CACHE_MASK)
>  
>  struct drm_msm_gem_new {
>  	__u64 size;           /* in */
> -- 
> 2.26.1
> 

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