linux-kernel - RE: [PATCH v1] scsi: ufs-mediatek: Enable UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH

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Date:   Thu, 24 Dec 2020 11:03:00 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Stanley Chu <stanley.chu@...iatek.com>,
        Can Guo <cang@...eaurora.org>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kuohong.wang@...iatek.com" <kuohong.wang@...iatek.com>,
        "peter.wang@...iatek.com" <peter.wang@...iatek.com>,
        "chun-hung.wu@...iatek.com" <chun-hung.wu@...iatek.com>,
        "andy.teng@...iatek.com" <andy.teng@...iatek.com>,
        "chaotian.jing@...iatek.com" <chaotian.jing@...iatek.com>,
        "cc.chou@...iatek.com" <cc.chou@...iatek.com>,
        "jiajie.hao@...iatek.com" <jiajie.hao@...iatek.com>,
        "alice.chao@...iatek.com" <alice.chao@...iatek.com>
Subject: RE: [PATCH v1] scsi: ufs-mediatek: Enable
 UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH_CTRL

Hi,
Just to clarify things:

> > Do you see any substantial benefit of having fWriteBoosterBufferFlushEn
> > disabled?
> 
> 1. The definition of fWriteBoosterBufferFlushEn is that host allows
> device to do flush in anytime after fWriteBoosterBufferFlushEn is set as
> on. This is not what we want.
> 
> Just Like BKOP, We do not want flush happening beyond host's expected
> timing that device performance may be "randomly" dropped.
Explicit flush takes place only when the device is idle:
if fWriteBoosterBufferFlushEn is set, the device is idle, and before h8 received.
If a request arrives, the flush operation should be halted.
So no performance degradation is expected. 

> 
> 2. Another related concern is that currently fWriteBoosterBufferFlushEn
> may keep on while device is not in Active Power Mode during suspend
> period. I am not sure if such configuration would confuse the device.
The spec says: " While the flushing operation is in progress, the device is in Active power mode"

> 
> Thanks,
> Stanley Chu
> 
> >
> > Thanks,
> > Can Guo.
> >
> > >
> > > Thanks,
> > >
> > > Can Guo.
> > >
> > >> Thanks,
> > >> Stanley Chu
> > >>>
> > >>> Change LGTM.
> > >>>
> > >>> Regards,
> > >>>
> > >>> Can Guo.