linux-kernel - [PATCH v8 03/12] iommu/mediatek: Add probe

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Date:   Wed, 29 Sep 2021 09:37:10 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>,
        Joerg Roedel <joro@...tes.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        David Airlie <airlied@...ux.ie>,
        "Mauro Carvalho Chehab" <mchehab@...nel.org>
CC:     Evan Green <evgreen@...omium.org>,
        Robin Murphy <robin.murphy@....com>,
        Tomasz Figa <tfiga@...omium.org>,
        Will Deacon <will.deacon@....com>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux-foundation.org>, <yong.wu@...iatek.com>,
        <youlin.pei@...iatek.com>, Matthias Kaehlcke <mka@...omium.org>,
        <anan.sun@...iatek.com>, <yi.kuo@...iatek.com>,
        <acourbot@...omium.org>, <linux-media@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, Daniel Vetter <daniel@...ll.ch>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Tiffany Lin <tiffany.lin@...iatek.com>,
        "Dafna Hirschfeld" <dafna.hirschfeld@...labora.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Eizan Miyamoto <eizan@...omium.org>,
        <anthony.huang@...iatek.com>,
        Frank Wunderlich <frank-w@...lic-files.de>
Subject: [PATCH v8 03/12] iommu/mediatek: Add probe_defer for smi-larb

Prepare for adding device_link.

The iommu consumer should use device_link to connect with the
smi-larb(supplier). then the smi-larb should run before the iommu
consumer. Here we delay the iommu driver until the smi driver is ready,
then all the iommu consumers always are after the smi driver.

When there is no this patch, if some consumer drivers run before
smi-larb, the supplier link_status is DL_DEV_NO_DRIVER(0) in the
device_link_add, then device_links_driver_bound will use WARN_ON
to complain that the link_status of supplier is not right.

device_is_bound may be more elegant here. but it is not allowed to
EXPORT from https://lore.kernel.org/patchwork/patch/1334670/.

Signed-off-by: Yong Wu <yong.wu@...iatek.com>
Tested-by: Frank Wunderlich <frank-w@...lic-files.de> # BPI-R2/MT7623
---
 drivers/iommu/mtk_iommu.c    | 2 +-
 drivers/iommu/mtk_iommu_v1.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index d837adfd1da5..d5848f78a677 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -844,7 +844,7 @@ static int mtk_iommu_probe(struct platform_device *pdev)
 			id = i;
 
 		plarbdev = of_find_device_by_node(larbnode);
-		if (!plarbdev) {
+		if (!plarbdev || !plarbdev->dev.driver) {
 			of_node_put(larbnode);
 			return -EPROBE_DEFER;
 		}
diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
index 1467ba1e4417..4d7809432239 100644
--- a/drivers/iommu/mtk_iommu_v1.c
+++ b/drivers/iommu/mtk_iommu_v1.c
@@ -602,7 +602,7 @@ static int mtk_iommu_probe(struct platform_device *pdev)
 		}
 
 		plarbdev = of_find_device_by_node(larbnode);
-		if (!plarbdev) {
+		if (!plarbdev || !plarbdev->dev.driver) {
 			of_node_put(larbnode);
 			return -EPROBE_DEFER;
 		}
-- 
2.18.0