linux-kernel - Re: [PATCH V6 2/6] scsi: ufs: qcom: Configure PA_VS_CORE_CLK_40NS

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Message-ID: <20230901153034.GS818859@hu-bjorande-lv.qualcomm.com>
Date:   Fri, 1 Sep 2023 08:30:34 -0700
From:   Bjorn Andersson <quic_bjorande@...cinc.com>
To:     Nitin Rawat <quic_nitirawa@...cinc.com>
CC:     <mani@...nel.org>, <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <jejb@...ux.ibm.com>,
        <martin.petersen@...cle.com>, <quic_cang@...cinc.com>,
        <quic_nguyenb@...cinc.com>, <linux-scsi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        "Naveen Kumar Goud Arepalli" <quic_narepall@...cinc.com>
Subject: Re: [PATCH V6 2/6] scsi: ufs: qcom: Configure
 PA_VS_CORE_CLK_40NS_CYCLES

On Fri, Sep 01, 2023 at 05:13:32PM +0530, Nitin Rawat wrote:
> Configure PA_VS_CORE_CLK_40NS_CYCLES with frequency of unipro core clk
> for Qualcomm UFS controller V4.0 and onwards to align with the hardware
> specification.
> 
> Co-developed-by: Naveen Kumar Goud Arepalli <quic_narepall@...cinc.com>
> Signed-off-by: Naveen Kumar Goud Arepalli <quic_narepall@...cinc.com>
> Signed-off-by: Nitin Rawat <quic_nitirawa@...cinc.com>
> ---
>  drivers/ufs/host/ufs-qcom.c | 47 ++++++++++++++++++++++++++++---------
>  drivers/ufs/host/ufs-qcom.h |  2 ++
>  2 files changed, 38 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> index fe36003faaa8..018e391c276e 100644
> --- a/drivers/ufs/host/ufs-qcom.c
> +++ b/drivers/ufs/host/ufs-qcom.c
> @@ -93,8 +93,9 @@ static const struct __ufs_qcom_bw_table {
>  static struct ufs_qcom_host *ufs_qcom_hosts[MAX_UFS_QCOM_HOSTS];
> 
>  static void ufs_qcom_get_default_testbus_cfg(struct ufs_qcom_host *host);
> -static int ufs_qcom_set_dme_vs_core_clk_ctrl_clear_div(struct ufs_hba *hba,
> -						       u32 clk_cycles);
> +static int ufs_qcom_set_core_clk_ctrl(struct ufs_hba *hba,
> +						       u32 clk_cycles,
> +						       u32 clk_40ns_cycles);
> 
>  static struct ufs_qcom_host *rcdev_to_ufs_host(struct reset_controller_dev *rcd)
>  {
> @@ -690,8 +691,8 @@ static int ufs_qcom_link_startup_notify(struct ufs_hba *hba,
>  			 * set unipro core clock cycles to 150 & clear clock
>  			 * divider
>  			 */
> -			err = ufs_qcom_set_dme_vs_core_clk_ctrl_clear_div(hba,
> -									  150);
> +			err = ufs_qcom_set_core_clk_ctrl(hba,
> +									  150, 6);

There's no reason to maintain the line wrap here, and the new
indentation looks wrong.

> 
>  		/*
>  		 * Some UFS devices (and may be host) have issues if LCC is
> @@ -1295,12 +1296,12 @@ static void ufs_qcom_exit(struct ufs_hba *hba)
>  	phy_power_off(host->generic_phy);
>  	phy_exit(host->generic_phy);
>  }
> -
> -static int ufs_qcom_set_dme_vs_core_clk_ctrl_clear_div(struct ufs_hba *hba,
> -						       u32 cycles_in_1us)
> +static int ufs_qcom_set_core_clk_ctrl(struct ufs_hba *hba,
> +					u32 cycles_in_1us,

Following my comment on this rename in the last commit, here you do
change the prototype, so here you need the rename to clarify the intent,
so make it here instead.

> +					u32 cycles_in_40ns)
>  {
>  	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> -	u32 core_clk_ctrl_reg;
> +	u32 core_clk_ctrl_reg, reg;

Please keep one variable declaration per line, in particular when using
names like "core_clk_ctrl_reg" which looks much more like a type than a
variable name...

I would have preferred "reg" instead of core_clk_ctrl_reg" and you could
have used that same variable for both sections.

>  	int ret;
> 
>  	ret = ufshcd_dme_get(hba,
> @@ -1325,9 +1326,33 @@ static int ufs_qcom_set_dme_vs_core_clk_ctrl_clear_div(struct ufs_hba *hba,
>  	/* Clear CORE_CLK_DIV_EN */
>  	core_clk_ctrl_reg &= ~DME_VS_CORE_CLK_CTRL_CORE_CLK_DIV_EN_BIT;
> 
> -	return ufshcd_dme_set(hba,
> +	err = ufshcd_dme_set(hba,

I might be confused, but didn't you remove "err" in patch 1? Does this
patch compile?

>  			    UIC_ARG_MIB(DME_VS_CORE_CLK_CTRL),
>  			    core_clk_ctrl_reg);
> +	/*
> +	 * UFS host controller V4.0.0 onwards needs to program
> +	 * PA_VS_CORE_CLK_40NS_CYCLES attribute per programmed
> +	 * frequency of unipro core clk of UFS host controller.
> +	 */
> +	if (!err && (host->hw_ver.major >= 4)) {

Rather than if (previous-block-didn't-fail), add an explicit return if
err is unfavourable. That will make it more obvious that this section
relates to version >= 4 and nothing else.


That said, you now have one function:

core_clk_ctrl(int a, int b)
{
	do stuff based on a;

	if (version > 4)
		do stuff based on b;
}

It's pretty much one function for cycles_in_1us, with a separate
function for cycles_in_40us bolted on at the end. How about just
splitting it in two functions instead, and provide a small wrapper that
calls one or both functions?

> +		if (cycles_in_40ns > PA_VS_CORE_CLK_40NS_CYCLES_MASK)
> +			return -EINVAL;
> +
> +		err = ufshcd_dme_get(hba,
> +				     UIC_ARG_MIB(PA_VS_CORE_CLK_40NS_CYCLES),
> +				     &reg);

Leaving this line unwrapped seems to end up at 89 characters wide.
Perfectly reasonable to do, in the name of readability.

> +		if (err)
> +			return err;
> +
> +		reg &= ~PA_VS_CORE_CLK_40NS_CYCLES_MASK;
> +		reg |= cycles_in_40ns;
> +
> +		err = ufshcd_dme_set(hba,
> +				     UIC_ARG_MIB(PA_VS_CORE_CLK_40NS_CYCLES),
> +				     reg);

Same as above.

Regards,
Bjorn