linux-kernel - Re: [PATCH v15 2/9] usb: dwc3: core: Access XHCI address space temporarily to read port info

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Date: Thu, 29 Feb 2024 10:47:19 +0100
From: Johan Hovold <johan@...nel.org>
To: Krishna Kurapati <quic_kriskura@...cinc.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Wesley Cheng <quic_wcheng@...cinc.com>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
	Felipe Balbi <balbi@...nel.org>, devicetree@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, quic_ppratap@...cinc.com,
	quic_jackp@...cinc.com
Subject: Re: [PATCH v15 2/9] usb: dwc3: core: Access XHCI address space
 temporarily to read port info

On Fri, Feb 16, 2024 at 06:27:49AM +0530, Krishna Kurapati wrote:
> Currently Multiport DWC3 controllers are host-only capable.

I already asked you to rephrase this so that it becomes clear that you
are describing a property of the current hardware (and similar
throughout the series):

	https://lore.kernel.org/all/ZTI7AtCJWgAnACSh@hovoldconsulting.com/

> +static int dwc3_read_port_info(struct dwc3 *dwc)
> +{
> +	void __iomem *base;
> +	u8 major_revision;
> +	u32 offset;
> +	u32 val;
> +
> +	/*
> +	 * Remap xHCI address space to access XHCI ext cap regs since it is
> +	 * needed to get information on number of ports present.
> +	 */
> +	base = ioremap(dwc->xhci_resources[0].start,
> +		       resource_size(&dwc->xhci_resources[0]));
> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	offset = 0;
> +	do {
> +		offset = xhci_find_next_ext_cap(base, offset,
> +						XHCI_EXT_CAPS_PROTOCOL);
> +		if (!offset)
> +			break;
> +
> +		val = readl(base + offset);
> +		major_revision = XHCI_EXT_PORT_MAJOR(val);
> +
> +		val = readl(base + offset + 0x08);
> +		if (major_revision == 0x03) {
> +			dwc->num_usb3_ports += XHCI_EXT_PORT_COUNT(val);
> +		} else if (major_revision <= 0x02) {
> +			dwc->num_usb2_ports += XHCI_EXT_PORT_COUNT(val);
> +		} else {
> +			dev_warn(dwc->dev,
> +				 "unrecognized port major revision %d\n",

I still think you should merge this with the previous line even if you
end up with 83 chars.

> +							major_revision);
> +		}
> +	} while (1);
 
> +	/*
> +	 * Currently only DWC3 controllers that are host-only capable
> +	 * support Multiport.
> +	 */

So again, also here, rephrase the comment so that it is clear that you
are referring to a property of the current hardware.

> +	hw_mode = DWC3_GHWPARAMS0_MODE(dwc->hwparams.hwparams0);
> +	if (hw_mode == DWC3_GHWPARAMS0_MODE_HOST) {
> +		ret = dwc3_read_port_info(dwc);
> +		if (ret)
> +			goto err_disable_clks;
> +	} else {
> +		dwc->num_usb2_ports = 1;
> +		dwc->num_usb3_ports = 1;
> +	}

Johan