Re: [PATCH 1/6] USB: serial: ftdi_sio: add configurable inter-batch defer for read URBs

[Greg Kroah-Hartman]

On Mon, Jun 22, 2026 at 09:05:53AM +0000, Chinna Mopurigari Naveen Kumar Reddy (FTDI-SG) wrote:
> Hi Greg,
> 
> On Mon, Jun 22, 2026 at 04:52:00PM +0000, Greg Kroah-Hartman wrote:
> > This is not the 1990's, module parameters should not be used anymore...
> > Why not just fix this at the root of the problem?
> 
> Thank you for the review, Greg.
> 
> You are right on both points.
> 
> On the module parameter: I will switch to sysfs if the per-driver approach
> is accepted, or drop it entirely.
> 
> On the location: your core point is well-taken. The DMA channel starvation
> is a BCM2835 DWC_OTG host controller deficiency, and the correct fix
> belongs in the host controller driver, not in each USB device driver.
> I will investigate fixing it there instead. If that is not feasible (the
> BCM2835 DWC_OTG is a vendor tree that Broadcom/RPi maintain outside
> mainline), I will report back before proposing any per-driver workaround.

As this is an out-of-tree issue, there's nothing we can do in our
in-tree drivers for that.  Please work with that team to either get
their code merged properly upstream with us, where we can all work on
the issue together, or just work with them out-of-tree.

thanks,

greg k-h