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SubjectRe: [PATCH v4 1/3] firmware: qcom_scm-64: Add atomic version of qcom_scm_call
Hi Stephen,

On 2019-09-06 20:42, Stephen Boyd wrote:
> 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 <vivek.gautam@codeaurora.org>
>> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
>> ---
>> 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);
>> +}
>> +

Have addressed all your comments in v5.

Thanks,
Sai

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