On Tue, Aug 6, 2019 at 3:58 AM Bjorn Andersson
<bjorn.andersson@xxxxxxxxxx> wrote:
>
> On Wed 19 Jun 04:34 PDT 2019, Vivek Gautam wrote:
>
> > On Tue, Jun 18, 2019 at 11:25 PM Will Deacon <will.deacon@xxxxxxx> wrote:
> > >
> > > On Wed, Jun 12, 2019 at 12:45:51PM +0530, Vivek Gautam wrote:
> > > > There are scnenarios where drivers are required to make a
> > > > scm call in atomic context, such as in one of the qcom's
> > > > arm-smmu-500 errata [1].
> > > >
> > > > [1] ("https://source.codeaurora.org/quic/la/kernel/msm-4.9/commit/
> > > > drivers/iommu/arm-smmu.c?h=CogSystems-msm-49/
> > > > msm-4.9&id=da765c6c75266b38191b38ef086274943f353ea7")
> > > >
> > > > Signed-off-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx>
> > > > Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> > > > ---
> > > > drivers/firmware/qcom_scm-64.c | 136 ++++++++++++++++++++++++++++-------------
> > > > 1 file changed, 92 insertions(+), 44 deletions(-)
> > > >
> > > > diff --git a/drivers/firmware/qcom_scm-64.c b/drivers/firmware/qcom_scm-64.c
> > > > index 91d5ad7cf58b..b6dca32c5ac4 100644
> > > > --- a/drivers/firmware/qcom_scm-64.c
> > > > +++ b/drivers/firmware/qcom_scm-64.c
> >
> > [snip]
> >
> > > > +
> > > > +static void qcom_scm_call_do(const struct qcom_scm_desc *desc,
> > > > + struct arm_smccc_res *res, u32 fn_id,
> > > > + u64 x5, bool atomic)
> > > > +{
> > >
> > > Maybe pass in the call type (ARM_SMCCC_FAST_CALL vs ARM_SMCCC_STD_CALL)
> > > instead of "bool atomic"? Would certainly make the callsites easier to
> > > understand.
> >
> > Sure, will do that.
> >
> > >
> > > > + int retry_count = 0;
> > > > +
> > > > + if (!atomic) {
> > > > + do {
> > > > + mutex_lock(&qcom_scm_lock);
> > > > +
> > > > + __qcom_scm_call_do(desc, res, fn_id, x5,
> > > > + ARM_SMCCC_STD_CALL);
> > > > +
> > > > + mutex_unlock(&qcom_scm_lock);
> > > > +
> > > > + if (res->a0 == QCOM_SCM_V2_EBUSY) {
> > > > + if (retry_count++ > QCOM_SCM_EBUSY_MAX_RETRY)
> > > > + break;
> > > > + msleep(QCOM_SCM_EBUSY_WAIT_MS);
> > > > + }
> > > > + } while (res->a0 == QCOM_SCM_V2_EBUSY);
> > > > + } else {
> > > > + __qcom_scm_call_do(desc, res, fn_id, x5, ARM_SMCCC_FAST_CALL);
> > > > + }
> > >
> > > Is it safe to make concurrent FAST calls?
> >
> > I better add a spinlock here.
> >
>
> Hi Vivek,
>
> Would you be able to respin this patch, so that we could unblock the
> introduction of the display nodes in the various device?
Will pointed [1] to the restructuring of arm-smmu to support
implementation specific details.
That hasn't been posted yet, and I haven't yet been able to work on that either.
I will be happy to respin this series with the comments addressed if
Will is okay to pull changes to unblock sdm845 devices. :)
[1] https://lore.kernel.org/patchwork/patch/1087457/
Thanks & Regards
Vivek
>
> Regards,
> Bjorn
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