linux-kernel - Re: [PATCH 2/2] usb: dwc3: core: Enable GUCTL1 bit 10 for fixing crc error after resume bug

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Date:   Fri, 17 Jun 2022 16:48:08 -0600
From:   Rob Herring <robh@...nel.org>
To:     Piyush Mehta <piyush.mehta@...inx.com>
Cc:     gregkh@...uxfoundation.org, krzysztof.kozlowski+dt@...aro.org,
        balbi@...nel.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        michal.simek@...inx.com, git@...inx.com, sivadur@...inx.com
Subject: Re: [PATCH 2/2] usb: dwc3: core: Enable GUCTL1 bit 10 for fixing crc
 error after resume bug

On Mon, Jun 13, 2022 at 06:17:03PM +0530, Piyush Mehta wrote:
> When configured in HOST mode, after issuing U3/L2 exit controller fails
> to send proper CRC checksum in CRC5 field. Because of this behavior
> Transaction Error is generated, resulting in reset and re-enumeration of
> usb device attached. Enabling chicken bit 10 of GUCTL1 will correct this
> problem.
> 
> When this bit is set to '1', the UTMI/ULPI opmode will be changed to
> "normal" along with HS terminations after EOR. This option is to support
> certain legacy UTMI/ULPI PHYs.
> 
> Signed-off-by: Piyush Mehta <piyush.mehta@...inx.com>
> ---
>  drivers/usb/dwc3/core.c | 16 ++++++++++++++++
>  drivers/usb/dwc3/core.h |  6 ++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index e027c0420dc3..8afc025390d2 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1140,6 +1140,20 @@ static int dwc3_core_init(struct dwc3 *dwc)
>  		dwc3_writel(dwc->regs, DWC3_GUCTL2, reg);
>  	}
>  
> +	/*
> +	 * When configured in HOST mode, after issuing U3/L2 exit controller
> +	 * fails to send proper CRC checksum in CRC5 feild. Because of this
> +	 * behaviour Transaction Error is generated, resulting in reset and
> +	 * re-enumeration of usb device attached. Enabling bit 10 of GUCTL1
> +	 * will correct this problem. This option is to support certain
> +	 * legacy ULPI PHYs.
> +	 */
> +	if (dwc->enable_guctl1_resume_quirk) {

What's the downside to just always doing this?

> +		reg = dwc3_readl(dwc->regs, DWC3_GUCTL1);
> +		reg |= DWC3_GUCTL1_RESUME_QUIRK;
> +		dwc3_writel(dwc->regs, DWC3_GUCTL1, reg);
> +	}
> +
>  	if (!DWC3_VER_IS_PRIOR(DWC3, 250A)) {
>  		reg = dwc3_readl(dwc->regs, DWC3_GUCTL1);
>  
> @@ -1483,6 +1497,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>  				"snps,dis-del-phy-power-chg-quirk");
>  	dwc->dis_tx_ipgap_linecheck_quirk = device_property_read_bool(dev,
>  				"snps,dis-tx-ipgap-linecheck-quirk");
> +	dwc->enable_guctl1_resume_quirk = device_property_read_bool(dev,
> +				"snps,enable_guctl1_resume_quirk");
>  	dwc->parkmode_disable_ss_quirk = device_property_read_bool(dev,
>  				"snps,parkmode-disable-ss-quirk");
>  
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index 81c486b3941c..e386209f0e1b 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -397,6 +397,9 @@
>  #define DWC3_GUCTL_REFCLKPER_MASK		0xffc00000
>  #define DWC3_GUCTL_REFCLKPER_SEL		22
>  
> +/* Global User Control Register 1 */
> +#define DWC3_GUCTL1_RESUME_QUIRK		BIT(10)
> +
>  /* Global User Control Register 2 */
>  #define DWC3_GUCTL2_RST_ACTBITLATER		BIT(14)
>  
> @@ -1093,6 +1096,8 @@ struct dwc3_scratchpad_array {
>   *			change quirk.
>   * @dis_tx_ipgap_linecheck_quirk: set if we disable u2mac linestate
>   *			check during HS transmit.
> + * @enable_guctl1_resume_quirk: Set if we enable quirk for fixing improper crc
> + *			generation after resume from suspend.
>   * @parkmode_disable_ss_quirk: set if we need to disable all SuperSpeed
>   *			instances in park mode.
>   * @tx_de_emphasis_quirk: set if we enable Tx de-emphasis quirk
> @@ -1308,6 +1313,7 @@ struct dwc3 {
>  	unsigned		dis_u2_freeclk_exists_quirk:1;
>  	unsigned		dis_del_phy_power_chg_quirk:1;
>  	unsigned		dis_tx_ipgap_linecheck_quirk:1;
> +	unsigned		enable_guctl1_resume_quirk:1;
>  	unsigned		parkmode_disable_ss_quirk:1;
>  
>  	unsigned		tx_de_emphasis_quirk:1;
> -- 
> 2.17.1
> 
>