linux-kernel - Re: [PATCH v2 2/4] firmware: scm: Modify only the DLOAD bit in TCSR register for download mode

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Message-ID: <bf17d901-5f0d-4f01-4498-9d1f254373f5@quicinc.com>
Date:   Thu, 16 Mar 2023 20:34:25 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>
CC:     <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] firmware: scm: Modify only the DLOAD bit in TCSR
 register for download mode



On 3/8/2023 8:36 PM, Srinivas Kandagatla wrote:
> 
> 
> On 01/03/2023 09:55, Mukesh Ojha 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.
>>
>> Originally-by: Poovendhan Selvaraj <quic_poovendh@...cinc.com>
>> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
>> ---
>> Changes in v2:
>>   - Addressed comment made by Bjorn.
>>   - Added download mask from patch 3 to this.
>>
>>   drivers/firmware/qcom_scm.c | 17 +++++++++++++++--
>>   1 file changed, 15 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
>> index 51eb853..c9f1fad 100644
>> --- a/drivers/firmware/qcom_scm.c
>> +++ b/drivers/firmware/qcom_scm.c
>> @@ -27,6 +27,8 @@ module_param(download_mode, bool, 0);
>>   #define SCM_HAS_IFACE_CLK    BIT(1)
>>   #define SCM_HAS_BUS_CLK        BIT(2)
>> +#define QCOM_DOWNLOAD_MODE_MASK 0x30
>> +
>>   struct qcom_scm {
>>       struct device *dev;
>>       struct clk *core_clk;
>> @@ -419,6 +421,7 @@ static void qcom_scm_set_download_mode(bool enable)
>>   {
>>       bool avail;
>>       int ret = 0;
>> +    u32 val;
>>       avail = __qcom_scm_is_call_available(__scm->dev,
>>                            QCOM_SCM_SVC_BOOT,
>> @@ -426,8 +429,18 @@ 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, &val);
>> +        if (ret) {
>> +            dev_err(__scm->dev,
>> +                "failed to read dload mode address value: %d\n", ret);
>> +            return;
>> +        }
>> +
>> +        val &= ~QCOM_DOWNLOAD_MODE_MASK;
>> +        if (enable)
>> +            val |= QCOM_SCM_BOOT_SET_DLOAD_MODE;
>> +
>> +        ret = qcom_scm_io_writel(__scm->dload_mode_addr, val);
> 
> 
> This is the second instance of such pattern of usage one is already in 
> ./drivers/pinctrl/qcom/pinctrl-msm.c
> 
> I think it makes sense to move setting fields in register to a dedicated 
> function like this:
> 
> int qcom_scm_io_update_field(phys_addr_t addr, unsigned int mask, 
> unsigned int val)
> {
>      unsigned int old, new;
>      int ret;
> 
>      ret = qcom_scm_io_readl(addr, &old);
>      if (ret)
>          return ret;
> 
>      new = (old & ~mask) | (val << ffs(mask) - 1);
> 
>      return qcom_scm_io_writel(addr, new);
> }
> EXPORT_SYMBOL(qcom_scm_io_update_field);
> 
> 
> then we could use it like this:
> ret = qcom_scm_io_update_field(__scm->dload_mode_addr, 
> QCOM_DOWNLOAD_MODE_MASK, dl_mode)

Thanks for the review,

will do it in v2, will let /drivers/pinctrl/qcom/pinctrl-msm.c uses this.

-Mukesh
> 
> 
> --srini
>>       } else {
>>           dev_err(__scm->dev,
>>               "No available mechanism for setting download mode\n");