linux-kernel - Re: [PATCH 1/1] scsi: ufs-mediatek: Add UFSHCD_QUIRK_BROKEN_LSDBS

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Message-ID: <20240822063436.nvll5cw3ifwonshz@thinkpad>
Date: Thu, 22 Aug 2024 12:04:36 +0530
From: Manivannan Sadhasivam <manisadhasivam.linux@...il.com>
To: Mary Guillemard <mary@...y.zone>
Cc: Bart Van Assche <bvanassche@....org>, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org, Peter Wang <peter.wang@...iatek.com>,
	Stanley Jhu <chu.stanley@...il.com>,
	"James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH 1/1] scsi: ufs-mediatek: Add UFSHCD_QUIRK_BROKEN_LSDBS_CAP

On Wed, Aug 21, 2024 at 11:32:06PM +0200, Mary Guillemard wrote:
> On Tue, Aug 20, 2024 at 02:50:58PM -0700, Bart Van Assche wrote:
> > On 8/19/24 11:09 PM, Manivannan Sadhasivam wrote:
> > > On Mon, Aug 19, 2024 at 08:17:10PM +0200, Mary Guillemard wrote:
> > > > On Mon, Aug 19, 2024 at 05:38:52PM +0530, Manivannan Sadhasivam wrote:
> > > > > On Mon, Aug 19, 2024 at 12:24:42AM +0200, Mary Guillemard wrote:
> > > > > > +	if (host->caps & UFS_MTK_CAP_DISABLE_MCQ)
> > > > > 
> > > > > How can this be the deciding factor? You said above that the issue is with
> > > > > MT8183 SoC. So why not just use the quirk only for that platform?
> > > > 
> > > > So my current assumption is that it also affect other Mediatek SoCs
> > > > that are also based on UFS 2.1 spec but I cannot check this.
> > > > 
> > > > Instead, we know that if MCQ isn't supported, we must fallback to LSDB
> > > > as there is no other ways to drive the device.
> > > > 
> > > > UFS_MTK_CAP_DISABLE_MCQ (mediatek,ufs-disable-mcq) being unused upstream,
> > > > I think that's an acceptable fix.
> > > > 
> > > 
> > > If you use this quirk, then you need to use the corresponding DT property. But
> > > using the 'mediatek,ufs-disable-mcq' property for 2.1 controller doesn't make
> > > sense as MCQ is for controllers >= 4.0.
> > > 
> > > > Another way to handle this would be to add a new dt property and add it
> > > > to ufs_mtk_host_caps but I feel that my approach should be enough.
> > > > 
> > > 
> > > No need to add a DT property. Just use the SoC specific compatible as I did for
> > > SM8550 SoC.
> > 
> > Mary, do you plan to implement Manivannan's feedback?
> > 
> > Thanks,
> > 
> > Bart.
> >
> 
> Hello Bart,
> 
> I think that considering Peter's reply, explicitly checking for the
> MT8183 controller isn't required.
> 
> I also think it could be required for at least the MT8192 and MT8195
> considering they are apparently also based on UFS 2.1 spec [1].
> 

How can you add a quirk that is specifically meant for 4.x controllers to 2.1
controllers? It doesn't make sense.

Also it is weird that the existing DT files doesn't have ufshc nodes for any
SoCs, but the SoCs are supporting UFSHC.

- Mani

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