From: Rob Clark <robdclark@gmail.com>
To: Bibek Kumar Patro <quic_bibekkum@quicinc.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
Konrad Dybcio <konrad.dybcio@linaro.org>,
will@kernel.org, robin.murphy@arm.com, joro@8bytes.org,
jsnitsel@redhat.com, quic_bjorande@quicinc.com, mani@kernel.org,
quic_eberman@quicinc.com, robdclark@chromium.org,
u.kleine-koenig@pengutronix.de, robh@kernel.org,
vladimir.oltean@nxp.com, quic_pkondeti@quicinc.com,
quic_molvera@quicinc.com, linux-arm-msm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v9 3/5] iommu/arm-smmu: introduction of ACTLR for custom prefetcher settings
Date: Tue, 4 Jun 2024 11:49:13 -0700 [thread overview]
Message-ID: <CAF6AEGsxKwzX6it4vipggOdGqNVzPbwMj6a0h871a=GfwUp0Cg@mail.gmail.com> (raw)
In-Reply-To: <9992067e-51c5-4a55-8d66-55a102a001b6@quicinc.com>
On Thu, May 30, 2024 at 2:22 AM Bibek Kumar Patro
<quic_bibekkum@quicinc.com> wrote:
>
>
>
> On 5/28/2024 9:38 PM, Rob Clark wrote:
> > On Tue, May 28, 2024 at 6:06 AM Dmitry Baryshkov
> > <dmitry.baryshkov@linaro.org> wrote:
> >>
> >> On Tue, May 28, 2024 at 02:59:51PM +0200, Konrad Dybcio wrote:
> >>>
> >>>
> >>> On 5/15/24 15:59, Bibek Kumar Patro wrote:
> >>>>
> >>>>
> >>>> On 5/10/2024 6:32 PM, Konrad Dybcio wrote:
> >>>>> On 10.05.2024 2:52 PM, Bibek Kumar Patro wrote:
> >>>>>>
> >>>>>>
> >>>>>> On 5/1/2024 12:30 AM, Rob Clark wrote:
> >>>>>>> On Tue, Jan 23, 2024 at 7:00 AM Bibek Kumar Patro
> >>>>>>> <quic_bibekkum@quicinc.com> wrote:
> >>>>>>>>
> >>>>>>>> Currently in Qualcomm SoCs the default prefetch is set to 1 which allows
> >>>>>>>> the TLB to fetch just the next page table. MMU-500 features ACTLR
> >>>>>>>> register which is implementation defined and is used for Qualcomm SoCs
> >>>>>>>> to have a custom prefetch setting enabling TLB to prefetch the next set
> >>>>>>>> of page tables accordingly allowing for faster translations.
> >>>>>>>>
> >>>>>>>> ACTLR value is unique for each SMR (Stream matching register) and stored
> >>>>>>>> in a pre-populated table. This value is set to the register during
> >>>>>>>> context bank initialisation.
> >>>>>>>>
> >>>>>>>> Signed-off-by: Bibek Kumar Patro <quic_bibekkum@quicinc.com>
> >>>>>>>> ---
> >>>>>
> >>>>> [...]
> >>>>>
> >>>>>>>> +
> >>>>>>>> + for_each_cfg_sme(cfg, fwspec, j, idx) {
> >>>>>>>> + smr = &smmu->smrs[idx];
> >>>>>>>> + if (smr_is_subset(smr, id, mask)) {
> >>>>>>>> + arm_smmu_cb_write(smmu, cbndx, ARM_SMMU_CB_ACTLR,
> >>>>>>>> + actlrcfg[i].actlr);
> >>>>>>>
> >>>>>>> So, this makes ACTLR look like kind of a FIFO. But I'm looking at
> >>>>>>> downstream kgsl's PRR thing (which we'll need to implement vulkan
> >>>>>>> sparse residency), and it appears to be wanting to set BIT(5) in ACTLR
> >>>>>>> to enable PRR.
> >>>>>>>
> >>>>>>> val = KGSL_IOMMU_GET_CTX_REG(ctx, KGSL_IOMMU_CTX_ACTLR);
> >>>>>>> val |= FIELD_PREP(KGSL_IOMMU_ACTLR_PRR_ENABLE, 1);
> >>>>>>> KGSL_IOMMU_SET_CTX_REG(ctx, KGSL_IOMMU_CTX_ACTLR, val);
> >>>>>>>
> >>>>>>> Any idea how this works? And does it need to be done before or after
> >>>>>>> the ACTLR programming done in this patch?
> >>>>>>>
> >>>>>>> BR,
> >>>>>>> -R
> >>>>>>>
> >>>>>>
> >>>>>> Hi Rob,
> >>>>>>
> >>>>>> Can you please help provide some more clarification on the FIFO part? By FIFO are you referring to the storing of ACTLR data in the table?
> >>>>>>
> >>>>>> Thanks for pointing to the downstream implementation of kgsl driver for
> >>>>>> the PRR bit. Since kgsl driver is already handling this PRR bit's
> >>>>>> setting, this makes setting the PRR BIT(5) by SMMU driver redundant.
> >>>>>
> >>>>> The kgsl driver is not present upstream.
> >>>>>
> >>>>
> >>>> Right kgsl is not present upstream, it would be better to avoid configuring the PRR bit and can be handled by kgsl directly in downstream.
> >>>
> >>> No! Upstream is not a dumping ground to reduce your technical debt.
> >>>
> >>> There is no kgsl driver upstream, so this ought to be handled here, in
> >>> the iommu driver (as poking at hardware A from driver B is usually not good
> >>> practice).
> >>
> >> I'd second the request here. If another driver has to control the
> >> behaviour of another driver, please add corresponding API for that.
> >
> > We have adreno_smmu_priv for this purpose ;-)
> >
>
> Thanks Rob for pointing to this private interface structure between smmu
> and gpu. I think it's similar to what you're trying to implement here
> https://lore.kernel.org/all/CAF6AEGtm-KweFdMFvahH1pWmpOq7dW_p0Xe_13aHGWt0jSbg8w@mail.gmail.com/#t
> I can add an api "set_actlr_prr()" with smmu_domain cookie, page pointer
> as two parameters. This api then can be used by drm/msm driver to carry
> out the prr implementation by simply calling this.
> Would this be okay Rob,Konrad,Dmitry?
> Let me know if any other suggestions you have in mind as well regarding
> parameters and placement.
Hey Bibek, quick question.. is ACTLR preserved across a suspend/resume
cycle? Or does it need to be reprogrammed on resume? And same
question for these two PRR related regs:
/* Global SMMU register offsets */
#define KGSL_IOMMU_PRR_CFG_LADDR 0x6008
#define KGSL_IOMMU_PRR_CFG_UADDR 0x600c
(ie. high/low 32b of the PRR page)
I was starting to type up a patch to add PRR configuration, but
depending on whether it interacts with suspend/resume, it might be
better form arm-smmu-qcom.c to just always enable and configure PRR
(including allocating a page to have an address to program into
PRR_CFG_LADDR/UADDR), and instead add an interface to return the PRR
page? I think there is no harm in unconditionally configuring PRR for
gpu smmu.
BR,
-R
> Thanks & regards,
> Bibek
>
> > BR,
> > -R
> >
> >>>
> >>>>
> >>>>>> Thanks for bringing up this point.
> >>>>>> I will send v10 patch series removing this BIT(5) setting from the ACTLR
> >>>>>> table.
> >>>>>
> >>>>> I think it's generally saner to configure the SMMU from the SMMU driver..
> >>>>
> >>>> Yes, agree on this. But since PRR bit is not directly related to SMMU
> >>>> configuration so I think it would be better to remove this PRR bit
> >>>> setting from SMMU driver based on my understanding.
> >>>
> >>> Why is it not related? We still don't know what it does.
> >>>
> >>> Konrad
> >>
> >> --
> >> With best wishes
> >> Dmitry
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next prev parent reply other threads:[~2024-06-04 18:49 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-23 14:45 [PATCH v9 0/5] iommu/arm-smmu: introduction of ACTLR implementation for Qualcomm SoCs Bibek Kumar Patro
2024-01-23 14:45 ` [PATCH v9 1/5] iommu/arm-smmu: re-enable context caching in smmu reset operation Bibek Kumar Patro
2024-01-23 14:45 ` [PATCH v9 2/5] iommu/arm-smmu: refactor qcom_smmu structure to include single pointer Bibek Kumar Patro
2024-01-23 14:45 ` [PATCH v9 3/5] iommu/arm-smmu: introduction of ACTLR for custom prefetcher settings Bibek Kumar Patro
2024-02-09 9:55 ` Bibek Kumar Patro
2024-02-09 10:53 ` Dmitry Baryshkov
2024-04-30 19:00 ` Rob Clark
2024-05-10 12:52 ` Bibek Kumar Patro
2024-05-10 13:02 ` Konrad Dybcio
2024-05-15 13:59 ` Bibek Kumar Patro
2024-05-28 12:59 ` Konrad Dybcio
2024-05-28 13:06 ` Dmitry Baryshkov
2024-05-28 16:08 ` Rob Clark
2024-05-28 16:09 ` Dmitry Baryshkov
2024-05-30 9:21 ` Bibek Kumar Patro
2024-05-30 11:18 ` Dmitry Baryshkov
2024-06-04 18:49 ` Rob Clark [this message]
2024-06-05 10:52 ` Bibek Kumar Patro
2024-06-05 22:13 ` Rob Clark
2024-06-10 10:12 ` Bibek Kumar Patro
2024-05-30 9:21 ` Bibek Kumar Patro
2024-05-30 9:21 ` Bibek Kumar Patro
2024-05-10 19:48 ` Rob Clark
2024-05-15 13:59 ` Bibek Kumar Patro
2024-01-23 14:45 ` [PATCH v9 4/5] iommu/arm-smmu: add ACTLR data and support for SM8550 Bibek Kumar Patro
2024-01-23 18:42 ` Konrad Dybcio
2024-02-13 13:47 ` Will Deacon
2024-02-21 8:55 ` Bibek Kumar Patro
2024-02-21 13:21 ` Will Deacon
2024-03-11 8:42 ` Bibek Kumar Patro
2024-01-23 14:45 ` [PATCH v9 5/5] iommu/arm-smmu: add ACTLR data and support for SC7280 Bibek Kumar Patro
2024-01-23 18:42 ` Konrad Dybcio
2024-04-30 17:59 ` [PATCH v9 0/5] iommu/arm-smmu: introduction of ACTLR implementation for Qualcomm SoCs Dmitry Baryshkov
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