Re: [PATCH V5 5/5] firmware: scm: Modify only the DLOAD bit in TCSR register for download mode

[Sricharan Ramabadhran <quic_srichara@quicinc.com>]

Hi,

On 2/20/2023 4:00 PM, POOVENDHAN SELVARAJ wrote:
> 
> On 2/18/2023 1:19 AM, Mukesh Ojha wrote:
>>
>>
>> On 2/16/2023 7:30 PM, Mukesh Ojha wrote:
>>>
>>>
>>> On 2/16/2023 5:30 PM, Poovendhan Selvaraj wrote:
>>>> CrashDump collection is based on the DLOAD bit of TCSR register.
>>>> To retain other bits, we read the register and modify only the DLOAD 
>>>> bit as
>>>> the other bits have their own significance.
>>>>
>>>> Co-developed-by: Anusha Rao <quic_anusha@quicinc.com>
>>>> Signed-off-by: Anusha Rao <quic_anusha@quicinc.com>
>>>> Co-developed-by: Kathiravan Thirumoorthy <quic_kathirav@quicinc.com>
>>>> Signed-off-by: Kathiravan Thirumoorthy <quic_kathirav@quicinc.com>
>>>> Signed-off-by: Poovendhan Selvaraj <quic_poovendh@quicinc.com>
>>>> ---
>>>>   Changes in V5:
>>>>     - checking the return value in qcom_scm_set_download_mode 
>>>> function as
>>>>       suggested by Srinivas Kandagatla
>>>>
>>>>   Changes in V4:
>>>>     - retain the orginal value of tcsr register when download mode
>>>>       is not set
>>>>
>>>>   drivers/firmware/qcom_scm.c | 21 ++++++++++++++++-----
>>>>   1 file changed, 16 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
>>>> index 468d4d5ab550..d88c5f14bd54 100644
>>>> --- a/drivers/firmware/qcom_scm.c
>>>> +++ b/drivers/firmware/qcom_scm.c
>>>> @@ -407,7 +407,7 @@ int qcom_scm_set_remote_state(u32 state, u32 id)
>>>>   }
>>>>   EXPORT_SYMBOL(qcom_scm_set_remote_state);
>>>> -static int __qcom_scm_set_dload_mode(struct device *dev, bool enable)
>>>> +static int __qcom_scm_set_dload_mode(struct device *dev, u32 val, 
>>>> bool enable)
>>>>   {
>>>>       struct qcom_scm_desc desc = {
>>>>           .svc = QCOM_SCM_SVC_BOOT,
>>>> @@ -417,7 +417,8 @@ static int __qcom_scm_set_dload_mode(struct 
>>>> device *dev, bool enable)
>>>>           .owner = ARM_SMCCC_OWNER_SIP,
>>>>       };
>>>> -    desc.args[1] = enable ? QCOM_SCM_BOOT_SET_DLOAD_MODE : 0;
>>>> +    desc.args[1] = enable ? val | QCOM_SCM_BOOT_SET_DLOAD_MODE :
>>>> +                val & ~(QCOM_SCM_BOOT_SET_DLOAD_MODE);
>>>>       return qcom_scm_call_atomic(__scm->dev, &desc, NULL);
>>>>   }
>>>> @@ -426,15 +427,25 @@ static void qcom_scm_set_download_mode(bool 
>>>> enable)
>>>>   {
>>>>       bool avail;
>>>>       int ret = 0;
>>>> +    u32 dload_addr_val;
>>>>       avail = __qcom_scm_is_call_available(__scm->dev,
>>>>                            QCOM_SCM_SVC_BOOT,
>>>>                            QCOM_SCM_BOOT_SET_DLOAD_MODE);
>>>> +    ret = qcom_scm_io_readl(__scm->dload_mode_addr, &dload_addr_val);
>>>> +
>>>> +    if (ret) {
>>>> +        dev_err(__scm->dev,
>>>> +            "failed to read dload mode address value: %d\n", ret);
>>>> +        return;
>>>> +    }
>>>> +
>>>>       if (avail) {
>>>> -        ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
>>>> +        ret = __qcom_scm_set_dload_mode(__scm->dev, dload_addr_val, 
>>>> enable);
>>>
>>> Did you test this on a target where it comes under this if statement? 
>>> does it really need to know dload_mode_addr for this target ?
>>
>>
>> Can we do something like this? I would let other review as well.
>>
>> --------------------------------------->0------------------------------------------- 
>>
>> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
>> index cdbfe54..26b7eda 100644
>> --- a/drivers/firmware/qcom_scm.c
>> +++ b/drivers/firmware/qcom_scm.c
>> @@ -419,6 +419,7 @@ static void qcom_scm_set_download_mode(bool enable)
>>  {
>>         bool avail;
>>         int ret = 0;
>> +       u32 dload_addr_val;
>>
>>         avail = __qcom_scm_is_call_available(__scm->dev,
>>                                              QCOM_SCM_SVC_BOOT,
>> @@ -426,8 +427,16 @@ static void qcom_scm_set_download_mode(bool enable)
>>         if (avail) {
>>                 ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
>>         } else if (__scm->dload_mode_addr) {
>> -               ret = qcom_scm_io_writel(__scm->dload_mode_addr,
>> -                               enable ? QCOM_SCM_BOOT_SET_DLOAD_MODE 
>> : 0);
>> +               ret = qcom_scm_io_readl(__scm->dload_mode_addr, 
>> &dload_addr_val);
>> +               if (ret) {
>> +                       dev_err(__scm->dev,
>> +                               "failed to read dload mode address 
>> value: %d\n", ret);
>> +                       return;
>> +               }
>> +
>> +               ret = qcom_scm_io_writel(__scm->dload_mode_addr, enable ?
>> +                               dload_addr_val | 
>> QCOM_SCM_BOOT_SET_DLOAD_MODE :
>> +                               dload_addr_val & 
>> ~(QCOM_SCM_BOOT_SET_DLOAD_MODE));
>>         } else {
>>                 dev_err(__scm->dev,
>>                         "No available mechanism for setting download 
>> mode\n");
>>
>> -Mukesh
> 
> Okay sure..Agreed, will address this in the next patch.

   Also, not sure, if its better to keep the old behavior working for
   targets that does not support 'READ' of this address. If one such
   thing exists, that will be broken now. In such a case, we should
   ignore if scm_io_readl fails, still write and dload_addr_val should
   be '0' initialised.


Regards,
  Sricharan