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Date:   Thu, 28 Apr 2022 15:36:34 +0900
From:   Jung Daehwan <dh10.jung@samsung.com>
To:     Krzysztof Kozlowski <krzk@kernel.org>
Cc:     Mathias Nyman <mathias.nyman@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "open list:USB XHCI DRIVER" <linux-usb@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        Howard Yen <howardyen@google.com>,
        Jack Pham <jackp@codeaurora.org>,
        Puma Hsu <pumahsu@google.com>,
        "J . Avila" <elavila@google.com>, sc.suh@samsung.com,
        Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Subject: Re: [PATCH v4 5/5] usb: host: add xhci-exynos driver
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On Thu, Apr 28, 2022 at 07:19:04AM +0200, Krzysztof Kozlowski wrote:
> On 28/04/2022 03:29, Jung Daehwan wrote:
> > On Tue, Apr 26, 2022 at 02:59:57PM +0200, Krzysztof Kozlowski wrote:
> >> On 26/04/2022 11:18, Daehwan Jung wrote:
> >>> This driver is for Samsung Exynos xhci host conroller. It uses xhci-plat
> >>> driver mainly and extends some functions by xhci hooks and overrides.
> >>>
> >>> It supports USB Audio offload with Co-processor. It only cares DCBAA,
> >>> Device Context, Transfer Ring, Event Ring, and ERST. They are allocated
> >>> on specific address with xhci hooks. Co-processor could use them directly
> >>> without xhci driver after then.
> >>
> >> This does not look like developed in current Linux kernel, but something
> >> out-of-tree, with some other unknown modifications. This is not how the
> >> code should be developed. Please rebase on linux-next and drop any
> >> unrelated modifications (these which are not sent with this patchset).
> >>
> > 
> > I've been developing on linux-next and I rebase before submitting.
> > Could you tell me one of dropped modifications or patches?
> > 
> >> (...)
> >>
> >>> +
> >>> +static int xhci_exynos_suspend(struct device *dev)
> >>> +{
> >>> +	struct usb_hcd	*hcd = dev_get_drvdata(dev);
> >>> +	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
> >>> +
> >>> +	/* TODO: AP sleep scenario*/
> >>
> >> Shall the patchset be called RFC?
> >>
> > OK. I will add RFC for this patch on next submission.
> > 
> >>> +
> >>> +	return xhci_suspend(xhci, device_may_wakeup(dev));
> >>> +}
> >>> +
> >>> +static int xhci_exynos_resume(struct device *dev)
> >>> +{
> >>> +	struct usb_hcd	*hcd = dev_get_drvdata(dev);
> >>> +	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
> >>> +	int ret;
> >>> +
> >>> +	/* TODO: AP resume scenario*/
> >>> +
> >>> +	ret = xhci_resume(xhci, 0);
> >>> +	if (ret)
> >>> +		return ret;
> >>> +
> >>> +	pm_runtime_disable(dev);
> >>> +	pm_runtime_set_active(dev);
> >>> +	pm_runtime_enable(dev);
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +static const struct dev_pm_ops xhci_exynos_pm_ops = {
> >>> +	SET_SYSTEM_SLEEP_PM_OPS(xhci_exynos_suspend, xhci_exynos_resume)
> >>> +};
> >>> +
> >>> +MODULE_DESCRIPTION("xHCI Exynos Host Controller Driver");
> >>> +MODULE_LICENSE("GPL");
> >>
> >> You don't have list of compatibles (and missing bindings), driver
> >> definition, driver registration. Entire solution is not used - nothing
> >> calls xhci_exynos_vendor_init(), because nothign uses "ops".
> >>
> > 
> > xhci_exynos_vendor_init is called in xhci-plat.c (xhci_vendor_init)
> > [v4,2/5] usb: host: add xhci hooks for xhci-exynos
> > ops are used in some files(xhci-mem.c, xhci.c ..) and the body of ops is in
> > all xhci-exynos.
> 
> 
> Nothing uses the "ops" except xhci_exynos_register_vendor_ops() which is
> not called anywhere, so the xhci_vendor_init() does not call
> xhci_exynos_vendor_init().
> 

You are right. xhci_exynos_register_vendor_ops should be called by other
module. It's only thing not called anywhere in this patchset. I don't uses
xhci-exynos alone in my scenario. Other module loads this on runtime.

> > 
> > xhci-exynos is not a standalone driver. It could be enabled when other module
> > makes xhci platform driver probed as it uses xhci platform mainly.
> 
> It "could be" or "will be"? We do not talk here about theoretical usage
> of the driver, but a real one.
> 
> > I thought I just used existing compltible not adding new one.
> > I will add them if needed.
> 
> Since you called everything here as "exynos" it is specific to one
> hardware and not-reusable on anything else. How can then you use some
> other compatible? It would be a misuse of Devicetree bindings.
> 

I got it. Let me add them. Is it still necessary if it is only used by
other module on runtime as I said above?

Best Regards,
Jung Daehwan

> Unless this is not specific to "exynos", but then please remove any
> exynos and vendor references and make it integrated in generic XHCI
> working for all drivers.
> 
> 
> >> This does not work and it makes it impossible to test it. Please provide
> >> proper XHCI Exynos driver, assuming you need it and it is not part of
> >> regular Exynos XHCI drivers (DWC3 and so on).
> >>
> > 
> > What makes you think it doesn't work?
> 
> Not possible to probe. The code cannot be loaded.
> 
> > I think it's almost proper. I just removed
> > other IPs code like Co-Processor(we call it abox) or Power Management because
> > it would make build-error. I've added hooking points in some files(xhci-mem.c,
> > xhci.c..) and ops are implemented in xhci-exynos. It's mainly operated with
> > xhci platform driver.
> 
> Best regards,
> Krzysztof
> 

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