linux-kernel - Re: [PATCH v2 2/3] ufs: core: Add a quirk for handling broken LSDBS field in controller capabilities register

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Message-ID: <20240816052414.GC2331@thinkpad>
Date: Fri, 16 Aug 2024 10:54:14 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Bart Van Assche <bvanassche@....org>
Cc: Alim Akhtar <alim.akhtar@...sung.com>,
	Avri Altman <avri.altman@....com>,
	"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, Kyoungrul Kim <k831.kim@...sung.com>,
	Amit Pundir <amit.pundir@...aro.org>
Subject: Re: [PATCH v2 2/3] ufs: core: Add a quirk for handling broken LSDBS
 field in controller capabilities register

On Thu, Aug 15, 2024 at 11:25:38AM -0700, Bart Van Assche wrote:
> On 8/14/24 10:16 PM, Manivannan Sadhasivam via B4 Relay wrote:
> > diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> > index 0b1787074215..8c9ff8696bcd 100644
> > --- a/drivers/ufs/core/ufshcd.c
> > +++ b/drivers/ufs/core/ufshcd.c
> > @@ -2426,7 +2426,11 @@ static inline int ufshcd_hba_capabilities(struct ufs_hba *hba)
> >   	 * 0h: legacy single doorbell support is available
> >   	 * 1h: indicate that legacy single doorbell support has been removed
> >   	 */
> > -	hba->lsdbs_sup = !FIELD_GET(MASK_LSDBS_SUPPORT, hba->capabilities);
> > +	if (!(hba->quirks & UFSHCD_QUIRK_BROKEN_LSDBS_CAP))
> > +		hba->lsdbs_sup = !FIELD_GET(MASK_LSDBS_SUPPORT, hba->capabilities);
> > +	else
> > +		hba->lsdbs_sup = true;
> > +
> >   	if (!hba->mcq_sup)
> >   		return 0;
> 
> An additional question: since the next patch only sets
> UFSHCD_QUIRK_BROKEN_LSDBS_CAP for a board with a UFSHCI 3.0 controller,
> do we really need the new quirk or can we replace the "!(hba->quirks &
> UFSHCD_QUIRK_BROKEN_LSDBS_CAP)" test with a test that verifies that the
> UFSHCI controller implements version 4.0 or later of the specification?
> 

Ok. First I made a mistake by believing that SM8550 is a 3.0 based controller.
But by looking into the internal documentation, I learned that it is a 4.0
controller without MCQ support. So version check is not possible (and I need to
fix the description as well).

Also, while looking into the version info I found that the Qcom driver sets
UFSHCD_QUIRK_BROKEN_UFS_HCI_VERSION quirk and the callback function
get_ufs_hci_version() just hardcodes the version to 2.0. But the recent SoCs do
reveal the UFSHCD version info correctly in REG_UFS_VERSION register. So the
quirk might only be applicable for 2.0 controllers (not sure if those are
supported now). Will check that and remove that quirk altogether.

- Mani

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