linux-kernel - Re: [PATCH v4 2/5] usb: host: add xhci hooks for xhci-exynos

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Date:   Wed, 27 Apr 2022 11:19:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jung Daehwan <dh10.jung@...sung.com>
Cc:     Mathias Nyman <mathias.nyman@...el.com>,
        "open list:USB XHCI DRIVER" <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Howard Yen <howardyen@...gle.com>,
        Jack Pham <jackp@...eaurora.org>,
        Puma Hsu <pumahsu@...gle.com>,
        "J . Avila" <elavila@...gle.com>, sc.suh@...sung.com,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Subject: Re: [PATCH v4 2/5] usb: host: add xhci hooks for xhci-exynos

On Wed, Apr 27, 2022 at 06:06:17PM +0900, Jung Daehwan wrote:
> On Tue, Apr 26, 2022 at 12:19:17PM +0200, Greg Kroah-Hartman wrote:
> > On Tue, Apr 26, 2022 at 06:18:45PM +0900, Daehwan Jung wrote:
> > > To enable supporting for USB offload, define "offload" in usb controller
> > > node of device tree. "offload" value can be used to determine which type
> > > of offload was been enabled in the SoC.
> > > 
> > > For example:
> > > 
> > > &usbdrd_dwc3 {
> > > 	...
> > > 	/* support usb offloading, 0: disabled, 1: audio */
> > > 	offload = <1>;
> > > 	...
> > > };
> > > 
> > > There are several vendor_ops introduced by this patch:
> > > 
> > > struct xhci_vendor_ops - function callbacks for vendor specific operations
> > > {
> > > 	@vendor_init:
> > > 		- called for vendor init process during xhci-plat-hcd
> > > 		  probe.
> > > 	@vendor_cleanup:
> > > 		- called for vendor cleanup process during xhci-plat-hcd
> > > 		  remove.
> > > 	@is_usb_offload_enabled:
> > > 		- called to check if usb offload enabled.
> > > 	@alloc_dcbaa:
> > > 		- called when allocating vendor specific dcbaa during
> > > 		  memory initializtion.
> > > 	@free_dcbaa:
> > > 		- called to free vendor specific dcbaa when cleanup the
> > > 		  memory.
> > > 	@alloc_transfer_ring:
> > > 		- called when vendor specific transfer ring allocation is required
> > > 	@free_transfer_ring:
> > > 		- called to free vendor specific transfer ring
> > > 	@sync_dev_ctx:
> > > 		- called when synchronization for device context is required
> > > }
> > > 
> > > The xhci hooks with prefix "xhci_vendor_" on the ops in xhci_vendor_ops.
> > > For example, vendor_init ops will be invoked by xhci_vendor_init() hook,
> > > is_usb_offload_enabled ops will be invoked by
> > > xhci_vendor_is_usb_offload_enabled(), and so on.
> > > 
> > > Signed-off-by: Daehwan Jung <dh10.jung@...sung.com>
> > > Signed-off-by: J. Avila <elavila@...gle.com>
> > > Signed-off-by: Puma Hsu <pumahsu@...gle.com>
> > > Signed-off-by: Howard Yen <howardyen@...gle.com>
> > > ---
> > >  drivers/usb/host/xhci-hub.c  |   5 ++
> > >  drivers/usb/host/xhci-mem.c  | 131 +++++++++++++++++++++++++++++++----
> > >  drivers/usb/host/xhci-plat.c |  44 +++++++++++-
> > >  drivers/usb/host/xhci-plat.h |   8 +++
> > >  drivers/usb/host/xhci.c      |  80 ++++++++++++++++++++-
> > >  drivers/usb/host/xhci.h      |  46 ++++++++++++
> > >  6 files changed, 296 insertions(+), 18 deletions(-)
> > 
> > Why do you need to "override" anything?  Why can't these just be added
> > to the current xhci_plat_priv structure and used that way like the
> > current xhci platform interface works?
> > 
> 
> "override" means above xhci hooks? Above hooks are for ring management.
> In fact, xhci platform doesn't care ring management. That's why I've added hooks
> not used xhci_plat_priv.

Why not add ring management ability to the platform interface instead?
That's what you want to control here, in your platform driver, right?

> > > diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> > > index 841617952ac7..e07c9c132061 100644
> > > --- a/drivers/usb/host/xhci-hub.c
> > > +++ b/drivers/usb/host/xhci-hub.c
> > > @@ -535,8 +535,13 @@ static int xhci_stop_device(struct xhci_hcd *xhci, int slot_id, int suspend)
> > >  	    cmd->status == COMP_COMMAND_RING_STOPPED) {
> > >  		xhci_warn(xhci, "Timeout while waiting for stop endpoint command\n");
> > >  		ret = -ETIME;
> > > +		goto cmd_cleanup;
> > >  	}
> > >  
> > > +	ret = xhci_vendor_sync_dev_ctx(xhci, slot_id);
> > > +	if (ret)
> > > +		xhci_warn(xhci, "Sync device context failed, ret=%d\n", ret);
> > 
> > Shouldn't the function have spit out an error if there was a problem?
> 
> It just reads and sync information about device context. That's why I think
> it's not critical to go error routime. But it needs to discuss.

Ok, it looks like this follows the other ways this driver works, that's
fine.

> > And no documentiaon for these global function?
> > 
> 
> I thought there's no need to add documentation. They are just functions to call
> vendor ops and there's documentation of vendor ops above. I could add it if needed.

Always try to add documentation for when you want others to use the new
functions, as it helps explain how to use them.

thanks,

greg k-h