Re: [PATCH v2 14/15] scsi: ufs: ufs-qcom: Add support for finding HS gear on new UFS versions

[Andrew Halaney <ahalaney@redhat.com>]

On Mon, Oct 31, 2022 at 11:32:16PM +0530, 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-device-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 | 31 ++++++++++++++++++++++++++++---
>  drivers/ufs/host/ufs-qcom.h |  4 ++++
>  2 files changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> index c93d2d38b43e..ca60a5b0292b 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_device_gear, max_hcd_gear, reg;
> +	int ret;
>  
>  	if (host->hw_ver.major == 0x1) {
>  		/*
> @@ -292,8 +295,29 @@ 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

Bikeshedding, but I think with this wording checking:

    host->hw_ver.major >= 0x4

is a little more readable, or at least for me when I read the comment I
had to jump back up to the else if statement.

Even without that change though

Reviewed-by: Andrew Halaney <ahalaney@redhat.com>

> +		 * 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-device-gear", &max_device_gear);
> +		if (ret)
> +			goto err_out;
> +
> +		/* Next get the max gear supported by the UFS controller */
> +		reg = ufshcd_readl(hba, REG_UFS_PARAM0);
> +		max_hcd_gear = UFS_QCOM_MAX_GEAR(reg);
> +
> +		/* Now return the minimum of both gears */
> +		return min(max_device_gear, max_hcd_gear);
>  	}
>  
> +err_out:
>  	/* Default is HS-G3 */
>  	return UFS_HS_G3;
>  }
> @@ -303,7 +327,7 @@ 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 +335,9 @@ 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 7fe928b82753..751ded3e3531 100644
> --- a/drivers/ufs/host/ufs-qcom.h
> +++ b/drivers/ufs/host/ufs-qcom.h
> @@ -94,6 +94,10 @@ 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 */
>  
> -- 
> 2.25.1
>