linux-kernel - Re: [PATCH V4 5/5] firmware: scm: Modify only the DLOAD bit in TCSR register for download mode

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Date:   Wed, 15 Feb 2023 15:17:48 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     POOVENDHAN SELVARAJ <quic_poovendh@...cinc.com>, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, lee@...nel.org,
        mturquette@...libre.com, sboyd@...nel.org,
        jassisinghbrar@...il.com, catalin.marinas@....com, will@...nel.org,
        shawnguo@...nel.org, arnd@...db.de, marcel.ziswiler@...adex.com,
        robimarko@...il.com, dmitry.baryshkov@...aro.org,
        nfraprado@...labora.com, broonie@...nel.org,
        quic_gurus@...cinc.com, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     quic_srichara@...cinc.com, quic_gokulsri@...cinc.com,
        quic_sjaganat@...cinc.com, quic_kathirav@...cinc.com,
        quic_arajkuma@...cinc.com, quic_anusha@...cinc.com,
        quic_devipriy@...cinc.com
Subject: Re: [PATCH V4 5/5] firmware: scm: Modify only the DLOAD bit in TCSR
 register for download mode



On 15/02/2023 10:55, POOVENDHAN SELVARAJ wrote:
> 
> On 2/14/2023 6:27 PM, Srinivas Kandagatla wrote:
>>
>>
>> On 14/02/2023 05:14, 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@...cinc.com>
>>> Signed-off-by: Anusha Rao <quic_anusha@...cinc.com>
>>> Co-developed-by: Kathiravan Thirumoorthy <quic_kathirav@...cinc.com>
>>> Signed-off-by: Kathiravan Thirumoorthy <quic_kathirav@...cinc.com>
>>> Signed-off-by: Poovendhan Selvaraj <quic_poovendh@...cinc.com>
>>> ---
>>>   Changes in V4:
>>>     - retain the orginal value of tcsr register when download mode
>>>       is not set
>>>
>>>   drivers/firmware/qcom_scm.c | 15 ++++++++++-----
>>>   1 file changed, 10 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
>>> index 468d4d5ab550..8a34b386ac3a 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);
>>
>> why not read the value here before setting the DLOAD Mode instead of 
>> doing it in qcom_scm_set_download_mode()?
>> that would make the code simple and readable.
> 
> dload_addr_val is used in both if and else if cases in 
> qcom_scm_set_download_mode(), so we read in qcom_scm_set_download_mode() 
> function and pass to __qcom_scm_set_dload_mode().

that is fine as it is, I missread else part as calling 
__qcom_scm_set_dload_mode() too.

just check the ret value should be good.

--srini


> 
>    if (avail) {
> -        ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
> *+        ret = __qcom_scm_set_dload_mode(__scm->dev, dload_addr_val, 
> 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_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 {
> 
>>
>>>         return qcom_scm_call_atomic(__scm->dev, &desc, NULL);
>>>   }
>>> @@ -426,15 +427,19 @@ 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);
>>> +
>> not checking ret value here before proceeding?
>>
> Okay, sure..will address in next patch series.
>>>       if (avail) {
>>> -        ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
>>> +        ret = __qcom_scm_set_dload_mode(__scm->dev, dload_addr_val, 
>>> 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_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");
> 
> Regards,
> Poovendhan S
>