Re: [PATCH] ufs: core: bsg: Add hibern8 enter/exit to ufshcd_send_bsg_uic_cmd

[Can Guo]

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@xxxxxxxxxxx>
> > ---
> >   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@xxxxxxxxxxxxxxxxxx/

Hope above info can help you.

Thanks,
Can Guo.