Re: [PATCH 14/15] scsi: ufs: ufs-qcom: Add support for finding HS gear on new UFS versions

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Sun, Oct 30, 2022 at 12:48:21AM +0300, Dmitry Baryshkov wrote:
> On 29/10/2022 17:16, Manivannan Sadhasivam wrote:
> > Starting from UFS controller v4, Qcom supports dual gear mode (i.e., the
> > controller/PHY can be configured to run in two gear speeds). But that
> > requires an agreement between the UFS controller and the UFS device.
> > This commit finds the max gear supported by both controller and device
> > then decides which one to use.
> > 
> > UFS controller's max gear can be read from the REG_UFS_PARAM0 register and
> > UFS device's max gear can be read from the "max-gear" devicetree property.
> > 
> > The UFS PHY also needs to be configured with the decided gear using the
> > phy_set_mode_ext() API.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> > ---
> >   drivers/ufs/host/ufs-qcom.c | 35 ++++++++++++++++++++++++++++++++---
> >   drivers/ufs/host/ufs-qcom.h |  4 ++++
> >   2 files changed, 36 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> > index f952cc76919f..268463e92d67 100644
> > --- a/drivers/ufs/host/ufs-qcom.c
> > +++ b/drivers/ufs/host/ufs-qcom.c
> > @@ -281,6 +281,9 @@ static int ufs_qcom_host_reset(struct ufs_hba *hba)
> >   static u32 ufs_qcom_get_hs_gear(struct ufs_hba *hba, u32 hs_gear)
> >   {
> >   	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> > +	struct device *dev = hba->dev;
> > +	u32 max_gear, hcd_max_gear, reg;
> > +	int ret;
> >   	if (host->hw_ver.major == 0x1) {
> >   		/*
> > @@ -292,8 +295,33 @@ static u32 ufs_qcom_get_hs_gear(struct ufs_hba *hba, u32 hs_gear)
> >   		 */
> >   		if (hs_gear > UFS_HS_G2)
> >   			return UFS_HS_G2;
> > +	} else if (host->hw_ver.major > 0x3) {
> > +		/*
> > +		 * Starting from UFS controller v4, Qcom supports dual gear mode (i.e., the
> > +		 * controller/PHY can be configured to run in two gear speeds). But that
> > +		 * requires an agreement between the UFS controller and the device. Below
> > +		 * code tries to find the max gear of both and decides which gear to use.
> > +		 *
> > +		 * First get the max gear supported by the UFS device if available.
> > +		 * If the property is not defined in devicetree, then use the default gear.
> > +		 */
> > +		ret = of_property_read_u32(dev->of_node, "max-gear", &max_gear);
> > +		if (ret)
> > +			goto err_out;
> 
> Can we detect the UFS device's max gear somehow? If not, the 'max-gear'
> property name doesn't sound good. Maybe calling it 'device-gear' would be
> better.
> 

UFS device probing depends on PHY init sequence. So technically we cannot know
the max gear of the device without using an init sequence, but this information
is static and should be known to a board manufacturer. That's why I decided to
use this property. Another option is to use a fixed init sequence for probing
the device and do a re-init after knowing it's max gear but that is not
recommended.

We need "max" keyword because this property specifies the maximum gear at which
the device could operate and not necessarily the gear at which it operates.
Maybe, "max-device-gear" would make it clear.

Thanks,
Mani

> > +
> > +		/* Next get the max gear supported by the UFS controller */
> > +		reg = ufshcd_readl(hba, REG_UFS_PARAM0);
> > +		hcd_max_gear = UFS_QCOM_MAX_GEAR(reg);
> > +
> > +		/*
> > +		 * Now compare both the gears. If the max gear supported by the UFS device
> > +		 * is compatible with UFS controller, then use the UFS device's max gear
> > +		 * speed. Otherwise, use the UFS controller supported max gear speed.
> > +		 */
> > +		return (max_gear <= hcd_max_gear) ? max_gear : hcd_max_gear;
> 
> return max(max_gear, hcd_max_gear); ?
> 
> >   	}
> > +err_out:
> >   	/* Default is HS-G3 */
> >   	return UFS_HS_G3;
> >   }
> > @@ -303,7 +331,7 @@ static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
> >   	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> >   	struct phy *phy = host->generic_phy;
> >   	int ret;
> > -	bool is_rate_B = UFS_QCOM_LIMIT_HS_RATE == PA_HS_MODE_B;
> > +	u32 hs_gear;
> >   	/* Reset UFS Host Controller and PHY */
> >   	ret = ufs_qcom_host_reset(hba);
> > @@ -311,8 +339,9 @@ static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
> >   		dev_warn(hba->dev, "%s: host reset returned %d\n",
> >   				  __func__, ret);
> > -	if (is_rate_B)
> > -		phy_set_mode(phy, PHY_MODE_UFS_HS_B);
> > +	/* UFS_HS_G2 is used here since that's the least gear supported by legacy Qcom platforms */
> > +	hs_gear = ufs_qcom_get_hs_gear(hba, UFS_HS_G2);
> > +	phy_set_mode_ext(phy, PHY_MODE_UFS_HS_B, hs_gear);
> >   	/* phy initialization - calibrate the phy */
> >   	ret = phy_init(phy);
> > diff --git a/drivers/ufs/host/ufs-qcom.h b/drivers/ufs/host/ufs-qcom.h
> > index 214ea50acab9..c93bc52ea848 100644
> > --- a/drivers/ufs/host/ufs-qcom.h
> > +++ b/drivers/ufs/host/ufs-qcom.h
> > @@ -89,6 +89,10 @@ enum {
> >   #define TMRLUT_HW_CGC_EN	BIT(6)
> >   #define OCSC_HW_CGC_EN		BIT(7)
> > +/* bit definitions for REG_UFS_PARAM0 */
> > +#define MAX_HS_GEAR_MASK	GENMASK(6, 4)
> > +#define UFS_QCOM_MAX_GEAR(x)	FIELD_GET(MAX_HS_GEAR_MASK, (x))
> > +
> >   /* bit definition for UFS_UFS_TEST_BUS_CTRL_n */
> >   #define TEST_BUS_SUB_SEL_MASK	GENMASK(4, 0)  /* All XXX_SEL fields are 5 bits wide */
> 
> -- 
> With best wishes
> Dmitry
> 

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