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Fri, 06 Sep 2019 08:12:48 -0700 (PDT) Received: from chromium.org ([2620:15c:202:1:fa53:7765:582b:82b9]) by smtp.gmail.com with ESMTPSA id u5sm5336849pfl.25.2019.09.06.08.12.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Sep 2019 08:12:48 -0700 (PDT) Message-ID: <5d727770.1c69fb81.c9062.ce60@mx.google.com> MIME-Version: 1.0 In-Reply-To: <20190823063248.13295-2-vivek.gautam@codeaurora.org> References: <20190823063248.13295-1-vivek.gautam@codeaurora.org> <20190823063248.13295-2-vivek.gautam@codeaurora.org> To: Vivek Gautam , agross@kernel.org, iommu@lists.linux-foundation.org, joro@8bytes.org, robin.murphy@arm.com, will.deacon@arm.com From: Stephen Boyd Subject: Re: [PATCH v4 1/3] firmware: qcom_scm-64: Add atomic version of qcom_scm_call User-Agent: alot/0.8.1 Date: Fri, 06 Sep 2019 08:12:47 -0700 Cc: linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, bjorn.andersson@linaro.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org Quoting Vivek Gautam (2019-08-22 23:32:46) > 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/ > tree/drivers/iommu/arm-smmu.c?h=msm-4.9#n4842") > > Signed-off-by: Vivek Gautam > Reviewed-by: Bjorn Andersson > --- > 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 > @@ -62,32 +62,71 @@ static DEFINE_MUTEX(qcom_scm_lock); > #define FIRST_EXT_ARG_IDX 3 > #define N_REGISTER_ARGS (MAX_QCOM_SCM_ARGS - N_EXT_QCOM_SCM_ARGS + 1) > > -/** > - * qcom_scm_call() - Invoke a syscall in the secure world > - * @dev: device > - * @svc_id: service identifier > - * @cmd_id: command identifier > - * @desc: Descriptor structure containing arguments and return values > - * > - * Sends a command to the SCM and waits for the command to finish processing. > - * This should *only* be called in pre-emptible context. > -*/ > -static int qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id, > - const struct qcom_scm_desc *desc, > - struct arm_smccc_res *res) > +static void __qcom_scm_call_do(const struct qcom_scm_desc *desc, > + struct arm_smccc_res *res, u32 fn_id, > + u64 x5, u32 type) > +{ > + u64 cmd; > + struct arm_smccc_quirk quirk = {.id = ARM_SMCCC_QUIRK_QCOM_A6}; Nitpick: Put spaces around braces please. > + > + cmd = ARM_SMCCC_CALL_VAL(type, qcom_smccc_convention, > + ARM_SMCCC_OWNER_SIP, fn_id); > + > + quirk.state.a6 = 0; > + > + do { > + arm_smccc_smc_quirk(cmd, desc->arginfo, desc->args[0], > + desc->args[1], desc->args[2], x5, > + quirk.state.a6, 0, res, &quirk); > + > + if (res->a0 == QCOM_SCM_INTERRUPTED) > + cmd = res->a0; > + > + } while (res->a0 == QCOM_SCM_INTERRUPTED); > +} > + > +static void qcom_scm_call_do(const struct qcom_scm_desc *desc, > + struct arm_smccc_res *res, u32 fn_id, > + u64 x5, bool atomic) > +{ > + 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); > + } To save on some indentation maybe you could write it like: if (atomic) { __qcom_scm_call_do(..) return; } do { mutex_lock(..) ... } while (..); > +} > + > +static int ___qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id, > + const struct qcom_scm_desc *desc, > + struct arm_smccc_res *res, bool atomic) > { > int arglen = desc->arginfo & 0xf; > - int retry_count = 0, i; > + int i; > u32 fn_id = QCOM_SCM_FNID(svc_id, cmd_id); > - u64 cmd, x5 = desc->args[FIRST_EXT_ARG_IDX]; > + u64 x5 = desc->args[FIRST_EXT_ARG_IDX]; > dma_addr_t args_phys = 0; > void *args_virt = NULL; > size_t alloc_len; > - struct arm_smccc_quirk quirk = {.id = ARM_SMCCC_QUIRK_QCOM_A6}; > + gfp_t flag = atomic ? GFP_ATOMIC : GFP_KERNEL; > > if (unlikely(arglen > N_REGISTER_ARGS)) { > alloc_len = N_EXT_QCOM_SCM_ARGS * sizeof(u64); > - args_virt = kzalloc(PAGE_ALIGN(alloc_len), GFP_KERNEL); > + args_virt = kzalloc(PAGE_ALIGN(alloc_len), flag); > > if (!args_virt) > return -ENOMEM; > @@ -156,6 +169,41 @@ static int qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id, > return 0; > } > > +/** > + * qcom_scm_call() - Invoke a syscall in the secure world > + * @dev: device > + * @svc_id: service identifier > + * @cmd_id: command identifier > + * @desc: Descriptor structure containing arguments and return values > + * > + * Sends a command to the SCM and waits for the command to finish processing. > + * This should *only* be called in pre-emptible context. Add a might_sleep() then? > + */ > +static int qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id, > + const struct qcom_scm_desc *desc, > + struct arm_smccc_res *res) > +{ > + return ___qcom_scm_call(dev, svc_id, cmd_id, desc, res, false); > +} > + > +/** > + * qcom_scm_call_atomic() - atomic variation of qcom_scm_call() > + * @dev: device > + * @svc_id: service identifier > + * @cmd_id: command identifier > + * @desc: Descriptor structure containing arguments and return values > + * @res: Structure containing results from SMC/HVC call > + * > + * Sends a command to the SCM and waits for the command to finish processing. > + * This should be called in atomic context only. Maybe add a cant_sleep()? > + */ > +static int qcom_scm_call_atomic(struct device *dev, u32 svc_id, u32 cmd_id, > + const struct qcom_scm_desc *desc, > + struct arm_smccc_res *res) > +{ > + return ___qcom_scm_call(dev, svc_id, cmd_id, desc, res, true); > +} > + _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu