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Subject: Re: [PATCH v4 8/8] scsi: ufs: Select INITIAL adapt for HS Gear4
To:     Can Guo <cang@codeaurora.org>, asutoshd@codeaurora.org,
        nguyenb@codeaurora.org, hongwus@codeaurora.org,
        rnayak@codeaurora.org, linux-scsi@vger.kernel.org,
        kernel-team@android.com, saravanak@google.com, salyzyn@google.com
Cc:     Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        Pedro Sousa <pedrom.sousa@synopsys.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Venkat Gopalakrishnan <venkatg@codeaurora.org>,
        Tomas Winkler <tomas.winkler@intel.com>,
        Bean Huo <beanhuo@micron.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Allison Randal <allison@lohutok.net>,
        open list <linux-kernel@vger.kernel.org>
References: <1579764349-15578-1-git-send-email-cang@codeaurora.org>
 <1579764349-15578-9-git-send-email-cang@codeaurora.org>
From:   Bart Van Assche <bvanassche@acm.org>
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Date:   Sat, 25 Jan 2020 19:38:08 -0800
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On 2020-01-22 23:25, Can Guo wrote:
> @@ -8422,7 +8433,8 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
>  	if ((hba->ufs_version != UFSHCI_VERSION_10) &&
>  	    (hba->ufs_version != UFSHCI_VERSION_11) &&
>  	    (hba->ufs_version != UFSHCI_VERSION_20) &&
> -	    (hba->ufs_version != UFSHCI_VERSION_21))
> +	    (hba->ufs_version != UFSHCI_VERSION_21) &&
> +	    (hba->ufs_version != UFSHCI_VERSION_30))
>  		dev_err(hba->dev, "invalid UFS version 0x%x\n",
>  			hba->ufs_version);

Is the UFS specification backwards compatible? Or in other words, does
the existing driver work fine for devices with a controller that
supports a newer version of the spec? I'm asking this because in Linux
kernel driver a version check that excludes newer controller versions is
very unusual. Can the above version check be removed in its entirety?

Thanks,

Bart.