linux-kernel - Re: [PATCH 0/5] Add UFS support for SM8750

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Message-ID: <20250210101338.boziqlrxl2cei775@thinkpad>
Date: Mon, 10 Feb 2025 15:43:38 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: neil.armstrong@...aro.org, quic_cang@...cinc.com
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
	Melody Olvera <quic_molvera@...cinc.com>,
	Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Avri Altman <avri.altman@....com>,
	Bart Van Assche <bvanassche@....org>,
	Bjorn Andersson <andersson@...nel.org>,
	Andy Gross <agross@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Satya Durga Srinivasu Prabhala <quic_satyap@...cinc.com>,
	Trilok Soni <quic_tsoni@...cinc.com>, linux-arm-msm@...r.kernel.org,
	linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	Nitin Rawat <quic_nitirawa@...cinc.com>,
	Manish Pandey <quic_mapa@...cinc.com>
Subject: Re: [PATCH 0/5] Add UFS support for SM8750

+ Can (for the MCQ query)

On Mon, Feb 10, 2025 at 10:39:04AM +0100, neil.armstrong@...aro.org wrote:
> On 09/02/2025 16:21, Manivannan Sadhasivam wrote:
> > On Fri, Feb 07, 2025 at 11:47:12PM +0100, Konrad Dybcio wrote:
> > > On 13.01.2025 10:46 PM, Melody Olvera wrote:
> > > > Add UFS support for SM8750 SoCs.
> > > > 
> > > > Signed-off-by: Melody Olvera <quic_molvera@...cinc.com>
> > > > ---
> > > > Nitin Rawat (5):
> > > >        dt-bindings: phy: qcom,sc8280xp-qmp-ufs-phy: Document the SM8750 QMP UFS PHY
> > > >        phy: qcom-qmp-ufs: Add PHY Configuration support for SM8750
> > > >        dt-bindings: ufs: qcom: Document the SM8750 UFS Controller
> > > >        arm64: dts: qcom: sm8750: Add UFS nodes for SM8750 SoC
> > > >        arm64: dts: qcom: sm8750: Add UFS nodes for SM8750 QRD and MTP boards
> > > 
> > > You still need the same workaround 8550/8650 have in the UFS driver
> > > (UFSHCD_QUIRK_BROKEN_LSDBS_CAP) for it to work reliably, or at least
> > > that was the case for me on a 8750 QRD.
> > > 
> > > Please check whether we can make that quirk apply based on ctrl
> > > version or so, so that we don't have to keep growing the compatible
> > > list in the driver.
> > > 
> > 
> > That would be a bizarre. When I added the quirk, I was told that it would affect
> > only SM8550 and SM8650 (this one I learned later). I'm not against applying the
> > quirk based on UFSHC version if the bug is carried forward, but that would be an
> > indication of bad design.
> 
> Isn't 8750 capable of using MCQ now ? because this is the whole issue behind
> this UFSHCD_QUIRK_BROKEN_LSDBS_CAP, it's supposed to use MCQ by default... but
> we don't.
> 
> Is there any news about that ? It's a clear regression against downstream, not
> having MCQ makes the UFS driver struggle to reach high bandwidth when the system
> is busy because we can't spread the load over all CPUs and we have only single
> queue to submit requests.
> 

There are hardware issues on SM8550 and SM8650(?) for the MCQ feature.
Apparently, Qcom carries the workaround in downstream, but I got tired of
pushing them to upstream the fix(es).

Maybe Can Guo can share what is the latest update on this.

- Mani

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