linux-kernel - Re: [PATCH v2 3/3] scsi: ufs: rockchip: init support for UFS

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Message-ID: <20240816075244.sbul4gsaem4skon4@thinkpad>
Date: Fri, 16 Aug 2024 13:22:44 +0530
From: Manivannan Sadhasivam <manisadhasivam.linux@...il.com>
To: Shawn Lin <shawn.lin@...k-chips.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"James E . J . Bottomley" <James.Bottomley@...senPartnership.com>,
	"Martin K . Petersen" <martin.petersen@...cle.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Avri Altman <avri.altman@....com>,
	Bart Van Assche <bvanassche@....org>,
	YiFeng Zhao <zyf@...k-chips.com>, Liang Chen <cl@...k-chips.com>,
	linux-scsi@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 3/3] scsi: ufs: rockchip: init support for UFS

On Tue, Aug 13, 2024 at 03:22:45PM +0800, Shawn Lin wrote:

[...]

> > > > For runtime PM case, it's the power-domain driver will power down the
> > > > controller and PHY if UFS stack is not active any more（autosuspend）.
> > > > 
> > > > For system PM case, it's the SoC's firmware to cutting of all the power
> > > > for controller/PHY and device.
> > > > 
> > > 
> > > Both cases are not matching the expectations of {rpm/spm}_lvl. So
> > > the platform
> > > (power domain or the firmware) should be fixed. What if the user sets the
> > > {rpm/spm}_lvl to 1? Will the platform power down the controller even
> > > then? If
> > > so, then I'd say that the platform is broken and should be fixed.
> > 
> > Ok, it seems I need to set {rpm/spm}_lvl = 6 if I want platform to power
> > down the controller for ultra power-saving. But I still need to add my
> > own system PM callback in that case to recovery the link first. Do I
> > misunderstand it?
> > 
> > And for the user who sets the rpm/spm level via
> > ufs_sysfs_pm_lvl_store(), I think there is no way to block it currently,
> > except that we need to fix the power-domain driver and Firmware to
> > respect the level and choose correct policy.
> > 
> > 
> > So in summary for what the next step I should to:
> > (1) Set {rpm/spm}_lvl = 6 in host driver to reflect the expectation
> > (2) Add own PM callbacks to recovery the link to meet the expectation
> > (3) Fix the broken behaviour of PD or Firmware to respect the actual
> > desired pm level if user changes the pm level.
> > 
> > 
> 
> Sorry, I misunderstood your comment, so the action should be
> (1) Set {rpm/spm}_lvl = 5 in host driver to reflect the expectation
> (2) Use ufshcd_system_suspend/resume, but keep our own runtime PM
> callbacks as we need a extra step to gate refclk.

Ok.

> (3) Fix the broken behaviour of PD or Firmware to respect the actual
> desired pm level if user changes the pm level.

If you do this, then you don't need (1), don't you?

- Mani

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