Re: [PATCH 03/10] drm/sun4i: Remove obsolete references to PHYS_OFFSET

From: "Jernej Škrabec" <jernej.skrabec@gmail.com>
To: Chen-Yu Tsai <wens@csie.org>, Maxime Ripard <mripard@kernel.org>,
	Samuel Holland <samuel@sholland.org>
Cc: devicetree@vger.kernel.org, Samuel Holland <samuel@sholland.org>,
	David Airlie <airlied@linux.ie>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	linux-sunxi@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 03/10] drm/sun4i: Remove obsolete references to PHYS_OFFSET
Date: Mon, 11 Apr 2022 17:37:49 +0200	[thread overview]
Message-ID: <3167527.44csPzL39Z@kista> (raw)
In-Reply-To: <20220411043423.37333-4-samuel@sholland.org>

Dne ponedeljek, 11. april 2022 ob 06:34:15 CEST je Samuel Holland napisal(a):
> commit b4bdc4fbf8d0 ("soc: sunxi: Deal with the MBUS DMA offsets in a
> central place") added a platform device notifier that sets the DMA
> offset for all of the display engine frontend and backend devices.
> 
> The code applying the offset to DMA buffer physical addresses was then
> removed from the backend driver in commit 756668ba682e ("drm/sun4i:
> backend: Remove the MBUS quirks"), but the code subtracting PHYS_OFFSET
> was left in the frontend driver.
> 
> As a result, the offset was applied twice in the frontend driver. This
> likely went unnoticed because it only affects specific configurations
> (scaling or certain pixel formats) where the frontend is used, on boards
> with both one of these older SoCs and more than 1 GB of DRAM.
> 
> In addition, the references to PHYS_OFFSET prevent compiling the driver
> on architectures where PHYS_OFFSET is not defined.
> 
> Fixes: b4bdc4fbf8d0 ("soc: sunxi: Deal with the MBUS DMA offsets in a central 
place")
> Signed-off-by: Samuel Holland <samuel@sholland.org>

Good catch! Actually, people complained about non-working display on 
Cubietruck IIRC, which has 2 GB of RAM.

Did you test this on HW?

Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>

Best regards,
Jernej

> ---
> 
>  drivers/gpu/drm/sun4i/sun4i_frontend.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun4i_frontend.c b/drivers/gpu/drm/sun4i/
sun4i_frontend.c
> index 56ae38389db0..462fae73eae9 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_frontend.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_frontend.c
> @@ -222,13 +222,11 @@ void sun4i_frontend_update_buffer(struct sun4i_frontend 
*frontend,
>  
>  	/* Set the physical address of the buffer in memory */
>  	paddr = drm_fb_cma_get_gem_addr(fb, state, 0);
> -	paddr -= PHYS_OFFSET;
>  	DRM_DEBUG_DRIVER("Setting buffer #0 address to %pad\n", &paddr);
>  	regmap_write(frontend->regs, SUN4I_FRONTEND_BUF_ADDR0_REG, paddr);
>  
>  	if (fb->format->num_planes > 1) {
>  		paddr = drm_fb_cma_get_gem_addr(fb, state, swap ? 2 : 
1);
> -		paddr -= PHYS_OFFSET;
>  		DRM_DEBUG_DRIVER("Setting buffer #1 address to %pad\n", 
&paddr);
>  		regmap_write(frontend->regs, 
SUN4I_FRONTEND_BUF_ADDR1_REG,
>  			     paddr);
> @@ -236,7 +234,6 @@ void sun4i_frontend_update_buffer(struct sun4i_frontend 
*frontend,
>  
>  	if (fb->format->num_planes > 2) {
>  		paddr = drm_fb_cma_get_gem_addr(fb, state, swap ? 1 : 
2);
> -		paddr -= PHYS_OFFSET;
>  		DRM_DEBUG_DRIVER("Setting buffer #2 address to %pad\n", 
&paddr);
>  		regmap_write(frontend->regs, 
SUN4I_FRONTEND_BUF_ADDR2_REG,
>  			     paddr);
> -- 
> 2.35.1
> 
> 