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[82.149.12.248]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43b51899617sm10663715f8f.31.2026.03.18.12.28.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 12:28:25 -0700 (PDT) From: Jernej =?UTF-8?B?xaBrcmFiZWM=?= To: Chen-Yu Tsai , Jernej Skrabec , Samuel Holland , wens@kernel.org Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , linux-sunxi@lists.linux.dev, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/sun4i: layers: Use drm_fb_dma_get_gem_addr() to get display memory Date: Wed, 18 Mar 2026 20:28:23 +0100 Message-ID: <6247601.lOV4Wx5bFT@jernej-laptop> In-Reply-To: References: <20260309165635.1138413-1-wens@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260318_122828_687759_2ABF96CF X-CRM114-Status: GOOD ( 24.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Dne sreda, 18. marec 2026 ob 10:35:35 Srednjeevropski standardni =C4=8Das j= e Chen-Yu Tsai napisal(a): > Hi, >=20 > On Tue, Mar 10, 2026 at 12:56=E2=80=AFAM Chen-Yu Tsai w= rote: > > > > Commit 4636ce93d5b2 ("drm/fb-cma-helper: Add drm_fb_cma_get_gem_addr()") > > adds a new helper, which covers fetching a drm_framebuffer's GEM object > > and calculating the buffer address for a given plane. > > > > This patch uses this helper to replace our own open coded version of the > > same function. > > > > Signed-off-by: Chen-Yu Tsai > > --- > > drivers/gpu/drm/sun4i/sun8i_ui_layer.c | 16 ++------------- > > drivers/gpu/drm/sun4i/sun8i_vi_layer.c | 27 ++------------------------ > > 2 files changed, 4 insertions(+), 39 deletions(-) > > > > diff --git a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c b/drivers/gpu/drm/s= un4i/sun8i_ui_layer.c > > index f08f6da55dd0..72c92203ae63 100644 > > --- a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c > > +++ b/drivers/gpu/drm/sun4i/sun8i_ui_layer.c > > @@ -124,25 +124,13 @@ static void sun8i_ui_layer_update_buffer(struct s= un8i_layer *layer, > > { > > struct drm_plane_state *state =3D plane->state; > > struct drm_framebuffer *fb =3D state->fb; > > - struct drm_gem_dma_object *gem; > > dma_addr_t dma_addr; > > u32 ch_base; > > - int bpp; > > > > ch_base =3D sun8i_channel_base(layer); > > > > - /* Get the physical address of the buffer in memory */ > > - gem =3D drm_fb_dma_get_gem_obj(fb, 0); > > - > > - DRM_DEBUG_DRIVER("Using GEM @ %pad\n", &gem->dma_addr); > > - > > - /* Compute the start of the displayed memory */ > > - bpp =3D fb->format->cpp[0]; > > - dma_addr =3D gem->dma_addr + fb->offsets[0]; > > - > > - /* Fixup framebuffer address for src coordinates */ > > - dma_addr +=3D (state->src.x1 >> 16) * bpp; > > - dma_addr +=3D (state->src.y1 >> 16) * fb->pitches[0]; > > + /* Get the start of the displayed memory */ > > + dma_addr =3D drm_fb_dma_get_gem_addr(fb, state, 0); >=20 > I just realized while reading more code that there's a subtle difference > here. >=20 > The original code used state->src.x1, which is the "clipped" coordinates, > while drm_fb_dma_get_gem_addr() uses state->src_x, which is the original > coordinates. >=20 > Jernej, do you know which one the driver is supposed to use? Or maybe > it doesn't matter? I would say that it doesn't matter for point of origin. Original coordinates use uint32_t values which means origin cannot be out of screen (negative numbers). What I found interesting is that clipped coordinates are int, e.g. they can be negative. Best regards, Jernej