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Date:   Thu, 16 May 2019 17:15:48 +0200
From:   Fredrik Noring <noring@nocrew.org>
To:     Laurentiu Tudor <laurentiu.tudor@nxp.com>
Cc:     Robin Murphy <robin.murphy@arm.com>, "hch@lst.de" <hch@lst.de>,
        "stern@rowland.harvard.edu" <stern@rowland.harvard.edu>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "marex@denx.de" <marex@denx.de>,
        "JuergenUrban@gmx.de" <JuergenUrban@gmx.de>,
        Leo Li <leoyang.li@nxp.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v2 0/3] prerequisites for device reserved local mem
 rework
Message-ID: <20190516151548.GB53952@sx9>
References: <20190514143807.7745-1-laurentiu.tudor@nxp.com>
 <9d34015d-c219-179b-3141-4b0de3530ac3@arm.com>
 <20190514182931.GA2559@sx9>
 <0e5f3b86-7a80-eec7-691b-34a123194208@nxp.com>
 <20190515162858.GB17162@sx9>
 <ed63c117-610c-ea49-f45e-727be220745f@nxp.com>
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Hi Laurentiu,

> I took your code, added the missing mapping and placed it in a patch. 
> Please see attached (compile tested only).

Thanks! Unfortunately, the OHCI fails with errors such as

	usb 1-1: device descriptor read/64, error -12

that I tracked down to the calls

	   hub_port_init
	-> usb_control_msg
	-> usb_internal_control_msg
	-> usb_start_wait_urb
	-> usb_submit_urb
	-> usb_hcd_submit_urb
	-> hcd->driver->urb_enqueue
	-> ohci_urb_enqueue
	-> ed_get
	-> ed_alloc
	-> dma_pool_zalloc
	-> dma_pool_alloc
	-> pool_alloc_page,

which returns NULL. Then I noticed

	/* pool_alloc_page() might sleep, so temporarily drop &pool->lock */

that might be a problem considering that the HCD handles pool memory in
IRQ handlers, for instance:

	   do_IRQ
	-> generic_handle_irq
	-> handle_level_irq
	-> handle_irq_event
	-> handle_irq_event_percpu
	-> __handle_irq_event_percpu
	-> usb_hcd_irq
	-> ohci_irq
	-> ohci_work
	-> finish_urb
	-> __usb_hcd_giveback_urb
	-> usb_hcd_unmap_urb_for_dma
	-> hcd_buffer_free

Also, DMA_BUFFER_SIZE in ohci-ps2.c is only 256 KiB in total. Is the new
pool implementation at least as efficient as the previous one?

Fredrik