Re: [PATCH v4 1/3] firmware: qcom_scm-64: Add atomic version of qcom_scm_call

[Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>]

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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