From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Wed, 24 Jan 2018 14:55:38 +0000 Subject: [PATCH v2] iommu/mediatek: Move attach_device after iommu-group is ready for M4Uv1 In-Reply-To: <1516696788-8668-1-git-send-email-yong.wu@mediatek.com> References: <1516696788-8668-1-git-send-email-yong.wu@mediatek.com> Message-ID: <78721402-989d-d06a-18cc-dd6efd358dfd@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 23/01/18 08:39, Yong Wu wrote: > In the commit 05f80300dc8b ("iommu: Finish making iommu_group support > mandatory"), the iommu framework has supposed all the iommu drivers have > their owner iommu-group, it get rid of the FIXME workarounds while the > group is NULL. But the flow of Mediatek M4U gen1 looks a bit trick that > it will hang at this case: > > ========================================== > Unable to handle kernel NULL pointer dereference at virtual address 00000030 > PC is at mutex_lock+0x28/0x54 > LR is at iommu_attach_device+0xa4/0xd4 > pc : [] lr : [] psr: 60000013 > sp : df0edbb8 ip : df0edbc8 fp : df0edbc4 > r10: c114da14 r9 : df2a3e40 r8 : 00000003 > r7 : df27a210 r6 : df2a90c4 r5 : 00000030 r4 : 00000000 > r3 : df0f8000 r2 : fffff000 r1 : df29c610 r0 : 00000030 > Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none > xxx > (mutex_lock) from [] (iommu_attach_device+0xa4/0xd4) > (iommu_attach_device) from [] (__arm_iommu_attach_device+0x28/0x90) > (__arm_iommu_attach_device) from [] (arm_iommu_attach_device+0x1c/0x30) > (arm_iommu_attach_device) from [] (mtk_iommu_add_device+0xfc/0x214) > (mtk_iommu_add_device) from [] (add_iommu_group+0x3c/0x68) > (add_iommu_group) from [] (bus_for_each_dev+0x78/0xac) > (bus_for_each_dev) from [] (bus_set_iommu+0xb0/0xec) > (bus_set_iommu) from [] (mtk_iommu_probe+0x328/0x368) > (mtk_iommu_probe) from [] (platform_drv_probe+0x5c/0xc0) > (platform_drv_probe) from [] (driver_probe_device+0x2f4/0x4d8) > (driver_probe_device) from [] (__driver_attach+0x10c/0x128) > (__driver_attach) from [] (bus_for_each_dev+0x78/0xac) > (bus_for_each_dev) from [] (driver_attach+0x2c/0x30) > (driver_attach) from [] (bus_add_driver+0x1e0/0x278) > (bus_add_driver) from [] (driver_register+0x88/0x108) > (driver_register) from [] (__platform_driver_register+0x50/0x58) > (__platform_driver_register) from [] (m4u_init+0x24/0x28) > (m4u_init) from [] (do_one_initcall+0xf0/0x17c) > ========================= > > The root cause is that "arm_iommu_attach_device" is called before > "iommu_group_get_for_dev" in the interface "mtk_iommu_add_device". Thus, > We adjust the sequence of this two functions. > > Unfortunately, there is another issue after the solution above, From the > function "iommu_attach_device", Only one device in each a iommu group is > allowed. In Mediatek case, there is only one m4u group, all the devices > are in one group. thus it get fail at this step. > > In order to satisfy this requirement, a new iommu group is allocated for > each a iommu consumer device. But meanwhile, we still have to use the > same domain for all the iommu group. Use a global variable "mtk_domain_v1" > to save the global domain. Argh, sorry for breaking it! Seems I managed to forget just how horrible and fiddly all the arm_iommu_* stuff is :( > CC: Robin Murphy > CC: Honghui Zhang > Fixes: 05f80300dc8b ("iommu: Finish making iommu_group support mandatory") > Reported-by: Ryder Lee > Tested-by: Bibby Hsieh > Signed-off-by: Yong Wu > --- > changes since v1: > Add mtk_domain_v1=NULL in domain_free for symmetry. > > v1: https://patchwork.kernel.org/patch/10176255/ > --- > drivers/iommu/mtk_iommu_v1.c | 42 +++++++++++++++++++----------------------- > 1 file changed, 19 insertions(+), 23 deletions(-) > > diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c > index 542930c..86106bf 100644 > --- a/drivers/iommu/mtk_iommu_v1.c > +++ b/drivers/iommu/mtk_iommu_v1.c > @@ -103,6 +103,9 @@ struct mtk_iommu_domain { > struct mtk_iommu_data *data; > }; > > +/* There is only a iommu domain in M4U gen1. */ > +static struct mtk_iommu_domain *mtk_domain_v1; > + > static struct mtk_iommu_domain *to_mtk_domain(struct iommu_domain *dom) > { > return container_of(dom, struct mtk_iommu_domain, domain); > @@ -251,10 +254,15 @@ static struct iommu_domain *mtk_iommu_domain_alloc(unsigned type) > if (type != IOMMU_DOMAIN_UNMANAGED) > return NULL; > > + /* Always return the same domain. */ > + if (mtk_domain_v1) > + return &mtk_domain_v1->domain; This seems a bit too fragile (and I vaguely recall we may have discussed and rejected this approach for the original driver), since any code doing: unused = iommu_domain_alloc(bus); iommu_domain_free(unused); will pull the rug out from under everyone's feet in a very nasty and unexpected manner. Given that mtk_iommu_create_mapping() is already a giant workaround for the ARM DMA code not understanding groups and default domains, I'd prefer not to have to regress "correct" driver behaviour for the sake of that; how about something like the below diff, is that enough to make things work? Robin. ----->8----- diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c index 542930cd183d..8b90b7a72238 100644 --- a/drivers/iommu/mtk_iommu_v1.c +++ b/drivers/iommu/mtk_iommu_v1.c @@ -376,6 +376,7 @@ static int mtk_iommu_create_mapping(struct device *dev, struct platform_device *m4updev; struct dma_iommu_mapping *mtk_mapping; struct device *m4udev; + struct iommu_group *group; int ret; if (args->args_count != 1) { @@ -418,6 +419,22 @@ static int mtk_iommu_create_mapping(struct device *dev, m4udev->archdata.iommu = mtk_mapping; } + /* + * This is a short-term bodge because the ARM DMA code doesn't + * understand multi-device groups, but we have to call into it + * successfully (and not just rely on a normal IOMMU API attach + * here) in order to set the correct DMA API ops on @dev. + */ + group = iommu_group_alloc(); + if (IS_ERR(group)) { + ret = ERR_PTR(group); + goto err_release_mapping; + } + ret = iommu_group_add_device(group, dev); + iommu_group_put(group); + if (ret) + goto err_release_mapping; + ret = arm_iommu_attach_device(dev, mtk_mapping); if (ret) goto err_release_mapping;