Messages in this thread | | | Date | Wed, 21 Jul 2021 16:01:24 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH -next] iommu/arm-smmu-v3: Add suspend and resume support |
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On Wed, 21 Jul 2021 14:59:47 +0100, Robin Murphy <robin.murphy@arm.com> wrote: > > On 2021-07-21 14:12, Marc Zyngier wrote: > > On Wed, 21 Jul 2021 12:42:14 +0100, > > Robin Murphy <robin.murphy@arm.com> wrote: > >> > >> [ +Marc for MSI bits ] > >> > >> On 2021-07-21 02:33, Bixuan Cui wrote: > >>> Add suspend and resume support for arm-smmu-v3 by low-power mode. > >>> > >>> When the smmu is suspended, it is powered off and the registers are > >>> cleared. So saves the msi_msg context during msi interrupt initialization > >>> of smmu. When resume happens it calls arm_smmu_device_reset() to restore > >>> the registers. > >>> > >>> Signed-off-by: Bixuan Cui <cuibixuan@huawei.com> > >>> Reviewed-by: Wei Yongjun <weiyongjun1@huawei.com> > >>> Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com> > >>> Reviewed-by: Ding Tianhong <dingtianhong@huawei.com> > >>> Reviewed-by: Hanjun Guo <guohanjun@huawei.com> > >>> --- > >>> > >>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 72 ++++++++++++++++++--- > >>> 1 file changed, 64 insertions(+), 8 deletions(-) > >>> > >>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >>> index 235f9bdaeaf2..bf1163acbcb1 100644 > >>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > >>> @@ -40,6 +40,7 @@ MODULE_PARM_DESC(disable_bypass, > >>> static bool disable_msipolling; > >>> module_param(disable_msipolling, bool, 0444); > >>> +static bool bypass; > >>> MODULE_PARM_DESC(disable_msipolling, > >>> "Disable MSI-based polling for CMD_SYNC completion."); > >>> @@ -3129,11 +3130,37 @@ static void arm_smmu_write_msi_msg(struct > >>> msi_desc *desc, struct msi_msg *msg) > >>> doorbell = (((u64)msg->address_hi) << 32) | msg->address_lo; > >>> doorbell &= MSI_CFG0_ADDR_MASK; > >>> + /* Saves the msg context for resume if desc->msg is empty */ > >>> + if (desc->msg.address_lo == 0 && desc->msg.address_hi == 0) { > >>> + desc->msg.address_lo = msg->address_lo; > >>> + desc->msg.address_hi = msg->address_hi; > >>> + desc->msg.data = msg->data; > >>> + } > >> > >> My gut feeling is that this is something a device driver maybe > >> shouldn't be poking into, but I'm not entirely familiar with the area > >> :/ > > > > Certainly not. If you rely on the message being stored into the > > descriptors, then implement this in the core code, like we do for PCI. > > Ah, so it would be an acceptable compromise to *read* desc->msg (and > thus avoid having to store our own copy of the message) if the core > was guaranteed to cache it? That's good to know, thanks.
Yeah, vfio, a couple of other weird drivers and (*surprise!*) ia64 are using this kind of trick. I don't see a reason not to implement that for platform-MSI (although level signalling may be interesting...), or even to move it into the core MSI code.
> > >>> + > >>> writeq_relaxed(doorbell, smmu->base + cfg[0]); > >>> writel_relaxed(msg->data, smmu->base + cfg[1]); > >>> writel_relaxed(ARM_SMMU_MEMATTR_DEVICE_nGnRE, smmu->base + cfg[2]); > >>> } > >>> +static void arm_smmu_resume_msis(struct arm_smmu_device *smmu) > >>> +{ > >>> + struct msi_desc *desc; > >>> + struct device *dev = smmu->dev; > >>> + > >>> + for_each_msi_entry(desc, dev) { > >>> + switch (desc->platform.msi_index) { > >>> + case EVTQ_MSI_INDEX: > >>> + case GERROR_MSI_INDEX: > >>> + case PRIQ_MSI_INDEX: > >>> + arm_smmu_write_msi_msg(desc, &(desc->msg)); > > > > Consider using get_cached_msi_msg() instead of using the internals of > > the descriptor. > > Oh, there's even a proper API for it, marvellous! I hadn't managed to > dig that far myself :)
It is a bit odd in the sense that it takes a copy of the message instead of returning a pointer, but at least this solves lifetime issues.
Thanks,
M.
-- Without deviation from the norm, progress is not possible.
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