linux-kernel - [PATCH 1/1] media: venus: core: Set dma maximum segment size

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Message-Id: <20181205083151.3685-1-vivek.gautam@codeaurora.org>
Date:   Wed,  5 Dec 2018 14:01:51 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     stanimir.varbanov@...aro.org, mchehab@...nel.org
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, vgarodia@...eaurora.org,
        acourbot@...omium.org, Vivek Gautam <vivek.gautam@...eaurora.org>
Subject: [PATCH 1/1] media: venus: core: Set dma maximum segment size

Turning on CONFIG_DMA_API_DEBUG_SG results in the following error:

[  460.308650] ------------[ cut here ]------------
[  460.313490] qcom-venus aa00000.video-codec: DMA-API: mapping sg segment longer than device claims to support [len=4194304] [max=65536]
[  460.326017] WARNING: CPU: 3 PID: 3555 at src/kernel/dma/debug.c:1301 debug_dma_map_sg+0x174/0x254
[  460.338888] Modules linked in: venus_dec venus_enc videobuf2_dma_sg videobuf2_memops hci_uart btqca bluetooth venus_core v4l2_mem2mem videobuf2_v4l2 videobuf2_common ath10k_snoc ath10k_core ath lzo lzo_compress zramjoydev
[  460.375811] CPU: 3 PID: 3555 Comm: V4L2DecoderThre Tainted: G        W         4.19.1 #82
[  460.384223] Hardware name: Google Cheza (rev1) (DT)
[  460.389251] pstate: 60400009 (nZCv daif +PAN -UAO)
[  460.394191] pc : debug_dma_map_sg+0x174/0x254
[  460.398680] lr : debug_dma_map_sg+0x174/0x254
[  460.403162] sp : ffffff80200c37d0
[  460.406583] x29: ffffff80200c3830 x28: 0000000000010000
[  460.412056] x27: 00000000ffffffff x26: ffffffc0f785ea80
[  460.417532] x25: 0000000000000000 x24: ffffffc0f4ea1290
[  460.423001] x23: ffffffc09e700300 x22: ffffffc0f4ea1290
[  460.428470] x21: ffffff8009037000 x20: 0000000000000001
[  460.433936] x19: ffffff80091b0000 x18: 0000000000000000
[  460.439411] x17: 0000000000000000 x16: 000000000000f251
[  460.444885] x15: 0000000000000006 x14: 0720072007200720
[  460.450354] x13: ffffff800af536e0 x12: 0000000000000000
[  460.455822] x11: 0000000000000000 x10: 0000000000000000
[  460.461288] x9 : 537944d9c6c48d00 x8 : 537944d9c6c48d00
[  460.466758] x7 : 0000000000000000 x6 : ffffffc0f8d98f80
[  460.472230] x5 : 0000000000000000 x4 : 0000000000000000
[  460.477703] x3 : 000000000000008a x2 : ffffffc0fdb13948
[  460.483170] x1 : ffffffc0fdb0b0b0 x0 : 000000000000007a
[  460.488640] Call trace:
[  460.491165]  debug_dma_map_sg+0x174/0x254
[  460.495307]  vb2_dma_sg_alloc+0x260/0x2dc [videobuf2_dma_sg]
[  460.501150]  __vb2_queue_alloc+0x164/0x374 [videobuf2_common]
[  460.507076]  vb2_core_reqbufs+0xfc/0x23c [videobuf2_common]
[  460.512815]  vb2_reqbufs+0x44/0x5c [videobuf2_v4l2]
[  460.517853]  v4l2_m2m_reqbufs+0x44/0x78 [v4l2_mem2mem]
[  460.523144]  v4l2_m2m_ioctl_reqbufs+0x1c/0x28 [v4l2_mem2mem]
[  460.528976]  v4l_reqbufs+0x30/0x40
[  460.532480]  __video_do_ioctl+0x36c/0x454
[  460.536610]  video_usercopy+0x25c/0x51c
[  460.540572]  video_ioctl2+0x38/0x48
[  460.544176]  v4l2_ioctl+0x60/0x74
[  460.547602]  do_video_ioctl+0x948/0x3520
[  460.551648]  v4l2_compat_ioctl32+0x60/0x98
[  460.555872]  __arm64_compat_sys_ioctl+0x134/0x20c
[  460.560718]  el0_svc_common+0x9c/0xe4
[  460.564498]  el0_svc_compat_handler+0x2c/0x38
[  460.568982]  el0_svc_compat+0x8/0x18
[  460.572672] ---[ end trace ce209b87b2f3af88 ]---

>From above warning one would deduce that the sg segment will overflow
the device's capacity. In reality, the hardware can accommodate larger
sg segments.
So, initialize the max segment size properly to weed out this warning.

Based on a similar patch sent by Sean Paul for mdss:
https://patchwork.kernel.org/patch/10671457/

Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
---
 drivers/media/platform/qcom/venus/core.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
index bb6add9d340e..5b8350e87e75 100644
--- a/drivers/media/platform/qcom/venus/core.c
+++ b/drivers/media/platform/qcom/venus/core.c
@@ -264,6 +264,14 @@ static int venus_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	if (!dev->dma_parms) {
+		dev->dma_parms = devm_kzalloc(dev, sizeof(*dev->dma_parms),
+					      GFP_KERNEL);
+		if (!dev->dma_parms)
+			return -ENOMEM;
+	}
+	dma_set_max_seg_size(dev, DMA_BIT_MASK(32));
+
 	INIT_LIST_HEAD(&core->instances);
 	mutex_init(&core->lock);
 	INIT_DELAYED_WORK(&core->work, venus_sys_error_handler);
-- 
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