linux-kernel - Re: [PATCH] ufs: core: bsg: Add hibern8 enter/exit to ufshcd_send_bsg_uic

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Message-ID: <c3f0d284-07d8-42a2-85d0-f4023b9b6bbc@quicinc.com>
Date: Thu, 6 Mar 2025 21:04:41 +0800
From: Can Guo <quic_cang@...cinc.com>
To: Bean Huo <huobean@...il.com>,
        Arthur Simchaev
	<arthur.simchaev@...disk.com>,
        <martin.petersen@...cle.com>, <quic_mapa@...cinc.com>
CC: <avri.altman@...disk.com>, <Avi.Shchislowski@...disk.com>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <bvanassche@....org>
Subject: Re: [PATCH] ufs: core: bsg: Add hibern8 enter/exit to
 ufshcd_send_bsg_uic_cmd

Hi Arthur,

On 3/6/2025 8:50 PM, Bean Huo wrote:
> Arthur,
>
> At present, we lack a user-space tool to initiate eye monitor
> measurements. Additionally, opening a channel for users in user land to
> send MP commands seems unsafe.
>
>
> Kind regards,
> Bean
>
> On Tue, 2025-03-04 at 13:46 +0200, Arthur Simchaev wrote:
>> Eye monitor measurement functionality was added to the M-PHY v5
>> specification. The measurement of the eye monitor signal for the UFS
>> device begins when the link enters the hibernate state.
>> Hence, allow user-layer applications the capability to send the
>> hibern8
>> enter command through the BSG framework. For completion, allow the
>> sibling functionality of hibern8 exit as well.
>>
>> Signed-off-by: Arthur Simchaev <arthur.simchaev@...disk.com>
>> ---
>>   drivers/ufs/core/ufshcd.c | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
>> index 4e1e214fc5a2..546ab557a77c 100644
>> --- a/drivers/ufs/core/ufshcd.c
>> +++ b/drivers/ufs/core/ufshcd.c
>> @@ -4366,6 +4366,16 @@ int ufshcd_send_bsg_uic_cmd(struct ufs_hba
>> *hba, struct uic_command *uic_cmd)
>>                  goto out;
>>          }
>>   
>> +       if (uic_cmd->command == UIC_CMD_DME_HIBER_ENTER) {
>> +               ret = ufshcd_uic_hibern8_enter(hba);
>> +               goto out;
>> +       }
>> +
>> +       if (uic_cmd->command == UIC_CMD_DME_HIBER_EXIT) {
>> +               ret = ufshcd_uic_hibern8_exit(hba);
>> +               goto out;
>> +       }
>> +
>>          mutex_lock(&hba->uic_cmd_mutex);
>>          ufshcd_add_delay_before_dme_cmd(hba);
>>   
>> --
>> 2.34.1
I can understand that you want to use hibern8 enter&exit to trigger a 
RCT to kick start the EOM,
however there is a better/simpler way to do so: you can trigger a power 
mode change to the
same power mode (e.g., from HS-G5 to HS-G5) to trigger a RCT (without 
invoking hibern8 enter&exit)
from user layer by dme_set(PA_PWRMODE).

FYI, we have open-sourced Qcom's EOM tool in GitHub and validated the 
EOM function on most
UFS4.x devices from UFS vendors, you can find the code for your reference:
https://github.com/quic/ufs-tools/blob/main/ufs-cli/ufs_eom.c#L266

The recent change from Ziqi Chen is to serve the power mode change 
purpose I mentioned above:
https://lore.kernel.org/all/20241212144248.990103107@linuxfoudation.org/

Hope above info can help you.

Thanks,
Can Guo.