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

[Krishna Kurapati PSSNV]

On 2/29/2024 3:17 PM, Johan Hovold wrote:
> 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@xxxxxxxxxxxxxxxxxxxx/

Hi Johan. Thanks for the review.

IMO, the statement is describing a property unique to current hardware, 
that "If it is a multiport controller, it is then host-only capable"

I used the word "Currently" to indicate that "Today, the multiport 
devices present...". Let me know if there is any ambiguity in the sentence.

In v13, I wrote:
"Currently host-only capable DWC3 controllers support Multiport."
You were right. It was ambiguous as it might refer to even single port 
controllers.

So I changed it saying all the DWC3 multiport controllers are host only 
capable.

How about:

"All the DWC3 Multi Port controllers that exist today only support host 
mode"

> > +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.

I put the comment this way to indicate that we don't want to check for 
existence of multiple ports if the controller is not "host-only" 
capable. We should only check for multport support only if we are 
host-only capable. I think the statement clearly tells that "check for 
host-only" configuration before proceeding to check for xhci register reads.

I replied the same on:
https://lore.kernel.org/all/279a54f2-7260-4270-83c7-d6f5c5ba0873@xxxxxxxxxxx/

And since you didn't mention anything else at this part of code in your 
return reply in:
https://lore.kernel.org/all/ZTYyXhyZN3jBXEfm@xxxxxxxxxxxxxxxxxxxx/

I thought this statement was fine to go.

> > +	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;
> > +	}

Thanks for the review. Can you help let me know your review on the other 
patches as well.

Regards,
Krishna,