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Message-ID: <90e27f2b-4512-6121-c5f4-e7cb87b259ab@quicinc.com>
Date:   Tue, 12 Sep 2023 16:39:07 -0700
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Subject: Re: [PATCH v3 1/2] usb: dwc3: core: configure TX/RX threshold for
 DWC3_IP
Content-Language: en-US
To:     Stanley Chang <stanley_chang@realtek.com>,
        Thinh Nguyen <Thinh.Nguyen@synopsys.com>
CC:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Felipe Balbi <balbi@kernel.org>, <linux-usb@vger.kernel.org>,
        <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20230912041904.30721-1-stanley_chang@realtek.com>
From:   Wesley Cheng <quic_wcheng@quicinc.com>
In-Reply-To: <20230912041904.30721-1-stanley_chang@realtek.com>
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Precedence: bulk

Hi,

On 9/11/2023 9:19 PM, Stanley Chang wrote:
> In Synopsys's dwc3 data book:
> To avoid underrun and overrun during the burst, in a high-latency bus
> system (like USB), threshold and burst size control is provided through
> GTXTHRCFG and GRXTHRCFG registers.
> 
> In Realtek DHC SoC, DWC3 USB 3.0 uses AHB system bus. When dwc3 is
> connected with USB 2.5G Ethernet, there will be overrun problem.
> Therefore, setting TX/RX thresholds can avoid this issue.
> 
> Signed-off-by: Stanley Chang <stanley_chang@realtek.com>
> ---
> v2 to v3 change:
>      Move the threshold setting to new function dwc3_config_threshold.
>      Add the threshold setting for usb31 and usb32
> v1 to v2 change:
>      Add the properties for TX/RX threshold setting
> ---
>   drivers/usb/dwc3/core.c | 160 +++++++++++++++++++++++++++++++---------
>   drivers/usb/dwc3/core.h |  13 ++++
>   2 files changed, 137 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 9c6bf054f15d..44ee8526dc28 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1057,6 +1057,111 @@ static void dwc3_set_power_down_clk_scale(struct dwc3 *dwc)
>   	}
>   }
>   
> +static void dwc3_config_threshold(struct dwc3 *dwc)
> +{
> +	u32 reg;
> +	u8 rx_thr_num;
> +	u8 rx_maxburst;
> +	u8 tx_thr_num;
> +	u8 tx_maxburst;
> +
> +	/*
> +	 * Must config both number of packets and max burst settings to enable
> +	 * RX and/or TX threshold.
> +	 */
> +	if (!DWC3_IP_IS(DWC3) && dwc->dr_mode == USB_DR_MODE_HOST) {
> +		rx_thr_num = dwc->rx_thr_num_pkt_prd;
> +		rx_maxburst = dwc->rx_max_burst_prd;
> +		tx_thr_num = dwc->tx_thr_num_pkt_prd;
> +		tx_maxburst = dwc->tx_max_burst_prd;
> +
> +		if (rx_thr_num && rx_maxburst) {
> +			reg = dwc3_readl(dwc->regs, DWC3_GRXTHRCFG);
> +			reg |= DWC31_RXTHRNUMPKTSEL_PRD;
> +
> +			reg &= ~DWC31_RXTHRNUMPKT_PRD(~0);
> +			reg |= DWC31_RXTHRNUMPKT_PRD(rx_thr_num);
> +
> +			reg &= ~DWC31_MAXRXBURSTSIZE_PRD(~0);
> +			reg |= DWC31_MAXRXBURSTSIZE_PRD(rx_maxburst);
> +
> +			dwc3_writel(dwc->regs, DWC3_GRXTHRCFG, reg);
> +		}
> +
> +		if (tx_thr_num && tx_maxburst) {
> +			reg = dwc3_readl(dwc->regs, DWC3_GTXTHRCFG);
> +			reg |= DWC31_TXTHRNUMPKTSEL_PRD;
> +
> +			reg &= ~DWC31_TXTHRNUMPKT_PRD(~0);
> +			reg |= DWC31_TXTHRNUMPKT_PRD(tx_thr_num);
> +
> +			reg &= ~DWC31_MAXTXBURSTSIZE_PRD(~0);
> +			reg |= DWC31_MAXTXBURSTSIZE_PRD(tx_maxburst);
> +
> +			dwc3_writel(dwc->regs, DWC3_GTXTHRCFG, reg);
> +		}
> +	}
> +
> +	rx_thr_num = dwc->rx_thr_num_pkt;
> +	rx_maxburst = dwc->rx_max_burst;
> +	tx_thr_num = dwc->tx_thr_num_pkt;
> +	tx_maxburst = dwc->tx_max_burst;
> +
> +	if (DWC3_IP_IS(DWC3)) {
> +		if (rx_thr_num && rx_maxburst) {
> +			reg = dwc3_readl(dwc->regs, DWC3_GRXTHRCFG);
> +			reg |= DWC3_GRXTHRCFG_PKTCNTSEL;
> +
> +			reg &= ~DWC3_GRXTHRCFG_RXPKTCNT(~0);
> +			reg |= DWC3_GRXTHRCFG_RXPKTCNT(rx_thr_num);
> +
> +			reg &= ~DWC3_GRXTHRCFG_MAXRXBURSTSIZE(~0);
> +			reg |= DWC3_GRXTHRCFG_MAXRXBURSTSIZE(rx_maxburst);
> +
> +			dwc3_writel(dwc->regs, DWC3_GRXTHRCFG, reg);
> +		}
> +
> +		if (tx_thr_num && tx_maxburst) {
> +			reg = dwc3_readl(dwc->regs, DWC3_GTXTHRCFG);
> +			reg |= DWC3_GTXTHRCFG_PKTCNTSEL;
> +
> +			reg &= ~DWC3_GTXTHRCFG_TXPKTCNT(~0);
> +			reg |= DWC3_GTXTHRCFG_TXPKTCNT(tx_thr_num);
> +
> +			reg &= ~DWC3_GTXTHRCFG_MAXTXBURSTSIZE(~0);
> +			reg |= DWC3_GTXTHRCFG_MAXTXBURSTSIZE(tx_maxburst);
> +
> +			dwc3_writel(dwc->regs, DWC3_GTXTHRCFG, reg);
> +		}
> +	} else {
> +		if (rx_thr_num && rx_maxburst) {
> +			reg = dwc3_readl(dwc->regs, DWC3_GRXTHRCFG);
> +			reg |= DWC31_GRXTHRCFG_PKTCNTSEL;
> +
> +			reg &= ~DWC31_GRXTHRCFG_RXPKTCNT(~0);
> +			reg |= DWC31_GRXTHRCFG_RXPKTCNT(rx_thr_num);
> +
> +			reg &= ~DWC31_GRXTHRCFG_MAXRXBURSTSIZE(~0);
> +			reg |= DWC31_GRXTHRCFG_MAXRXBURSTSIZE(rx_maxburst);
> +
> +			dwc3_writel(dwc->regs, DWC3_GRXTHRCFG, reg);
> +		}
> +
> +		if (tx_thr_num && tx_maxburst) {
> +			reg = dwc3_readl(dwc->regs, DWC3_GTXTHRCFG);
> +			reg |= DWC31_GTXTHRCFG_PKTCNTSEL;
> +
> +			reg &= ~DWC31_GTXTHRCFG_TXPKTCNT(~0);
> +			reg |= DWC31_GTXTHRCFG_TXPKTCNT(tx_thr_num);
> +
> +			reg &= ~DWC31_GTXTHRCFG_MAXTXBURSTSIZE(~0);
> +			reg |= DWC31_GTXTHRCFG_MAXTXBURSTSIZE(tx_maxburst);
> +
> +			dwc3_writel(dwc->regs, DWC3_GTXTHRCFG, reg);
> +		}
> +	}
> +}
> +
>   /**
>    * dwc3_core_init - Low-level initialization of DWC3 Core
>    * @dwc: Pointer to our controller context structure
> @@ -1209,42 +1314,7 @@ static int dwc3_core_init(struct dwc3 *dwc)
>   		dwc3_writel(dwc->regs, DWC3_GUCTL1, reg);
>   	}
>   
> -	/*
> -	 * Must config both number of packets and max burst settings to enable
> -	 * RX and/or TX threshold.
> -	 */
> -	if (!DWC3_IP_IS(DWC3) && dwc->dr_mode == USB_DR_MODE_HOST) {
> -		u8 rx_thr_num = dwc->rx_thr_num_pkt_prd;
> -		u8 rx_maxburst = dwc->rx_max_burst_prd;
> -		u8 tx_thr_num = dwc->tx_thr_num_pkt_prd;
> -		u8 tx_maxburst = dwc->tx_max_burst_prd;
> -
> -		if (rx_thr_num && rx_maxburst) {
> -			reg = dwc3_readl(dwc->regs, DWC3_GRXTHRCFG);
> -			reg |= DWC31_RXTHRNUMPKTSEL_PRD;
> -
> -			reg &= ~DWC31_RXTHRNUMPKT_PRD(~0);
> -			reg |= DWC31_RXTHRNUMPKT_PRD(rx_thr_num);
> -
> -			reg &= ~DWC31_MAXRXBURSTSIZE_PRD(~0);
> -			reg |= DWC31_MAXRXBURSTSIZE_PRD(rx_maxburst);
> -
> -			dwc3_writel(dwc->regs, DWC3_GRXTHRCFG, reg);
> -		}
> -
> -		if (tx_thr_num && tx_maxburst) {
> -			reg = dwc3_readl(dwc->regs, DWC3_GTXTHRCFG);
> -			reg |= DWC31_TXTHRNUMPKTSEL_PRD;
> -
> -			reg &= ~DWC31_TXTHRNUMPKT_PRD(~0);
> -			reg |= DWC31_TXTHRNUMPKT_PRD(tx_thr_num);
> -
> -			reg &= ~DWC31_MAXTXBURSTSIZE_PRD(~0);
> -			reg |= DWC31_MAXTXBURSTSIZE_PRD(tx_maxburst);
> -
> -			dwc3_writel(dwc->regs, DWC3_GTXTHRCFG, reg);
> -		}
> -	}
> +	dwc3_config_threshold(dwc);
>   
>   	return 0;
>   
> @@ -1380,6 +1450,10 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>   	u8			lpm_nyet_threshold;
>   	u8			tx_de_emphasis;
>   	u8			hird_threshold;
> +	u8			rx_thr_num_pkt = 0;
> +	u8			rx_max_burst = 0;
> +	u8			tx_thr_num_pkt = 0;
> +	u8			tx_max_burst = 0;
>   	u8			rx_thr_num_pkt_prd = 0;
>   	u8			rx_max_burst_prd = 0;
>   	u8			tx_thr_num_pkt_prd = 0;
> @@ -1442,6 +1516,14 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>   				"snps,usb2-lpm-disable");
>   	dwc->usb2_gadget_lpm_disable = device_property_read_bool(dev,
>   				"snps,usb2-gadget-lpm-disable");
> +	device_property_read_u8(dev, "snps,rx-thr-num-pkt",
> +				&rx_thr_num_pkt);
> +	device_property_read_u8(dev, "snps,rx-max-burst",
> +				&rx_max_burst);
> +	device_property_read_u8(dev, "snps,tx-thr-num-pkt",
> +				&tx_thr_num_pkt);
> +	device_property_read_u8(dev, "snps,tx-max-burst",
> +				&tx_max_burst);

Aren't there value limitations for some of these (if not all) settings? 
  For example, in the DWC3 programming guide, the max burst fields say 
(for DWC31):
	"Note: This field can only be set to 2, 4, 8 or 16."

And for the packet threshold count:
	"Valid values are from 1 to 16."

Thanks
Wesley Cheng

>   	device_property_read_u8(dev, "snps,rx-thr-num-pkt-prd",
>   				&rx_thr_num_pkt_prd);
>   	device_property_read_u8(dev, "snps,rx-max-burst-prd",
> @@ -1523,6 +1605,12 @@ static void dwc3_get_properties(struct dwc3 *dwc)
>   
>   	dwc->hird_threshold = hird_threshold;
>   
> +	dwc->rx_thr_num_pkt = rx_thr_num_pkt;
> +	dwc->rx_max_burst = rx_max_burst;
> +
> +	dwc->tx_thr_num_pkt = tx_thr_num_pkt;
> +	dwc->tx_max_burst = tx_max_burst;
> +
>   	dwc->rx_thr_num_pkt_prd = rx_thr_num_pkt_prd;
>   	dwc->rx_max_burst_prd = rx_max_burst_prd;
>   
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index a69ac67d89fe..6782ec8bfd64 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -211,6 +211,11 @@
>   #define DWC3_GRXTHRCFG_RXPKTCNT(n) (((n) & 0xf) << 24)
>   #define DWC3_GRXTHRCFG_PKTCNTSEL BIT(29)
>   
> +/* Global TX Threshold Configuration Register */
> +#define DWC3_GTXTHRCFG_MAXTXBURSTSIZE(n) (((n) & 0xff) << 16)
> +#define DWC3_GTXTHRCFG_TXPKTCNT(n) (((n) & 0xf) << 24)
> +#define DWC3_GTXTHRCFG_PKTCNTSEL BIT(29)
> +
>   /* Global RX Threshold Configuration Register for DWC_usb31 only */
>   #define DWC31_GRXTHRCFG_MAXRXBURSTSIZE(n)	(((n) & 0x1f) << 16)
>   #define DWC31_GRXTHRCFG_RXPKTCNT(n)		(((n) & 0x1f) << 21)
> @@ -1045,6 +1050,10 @@ struct dwc3_scratchpad_array {
>    * @test_mode_nr: test feature selector
>    * @lpm_nyet_threshold: LPM NYET response threshold
>    * @hird_threshold: HIRD threshold
> + * @rx_thr_num_pkt: USB receive packet count
> + * @rx_max_burst: max USB receive burst size
> + * @tx_thr_num_pkt: USB transmit packet count
> + * @tx_max_burst: max USB transmit burst size
>    * @rx_thr_num_pkt_prd: periodic ESS receive packet count
>    * @rx_max_burst_prd: max periodic ESS receive burst size
>    * @tx_thr_num_pkt_prd: periodic ESS transmit packet count
> @@ -1273,6 +1282,10 @@ struct dwc3 {
>   	u8			test_mode_nr;
>   	u8			lpm_nyet_threshold;
>   	u8			hird_threshold;
> +	u8			rx_thr_num_pkt;
> +	u8			rx_max_burst;
> +	u8			tx_thr_num_pkt;
> +	u8			tx_max_burst;
>   	u8			rx_thr_num_pkt_prd;
>   	u8			rx_max_burst_prd;
>   	u8			tx_thr_num_pkt_prd;