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Date: Sun, 5 Oct 2014 15:52:21 +0200
From: meino.cramer@gmx.de
To: Gentoo <gentoo-user@lists.gentoo.org>
Subject: [gentoo-user] Cohorent pool size too small...
Message-ID: <20141005135221.GC3856@solfire>
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Hi,

while trying to get a mt7601sta (UWN200 WiFi dongle) driver running
and working I came accross this in the dmesg output:

[    9.931938] usb 2-1: device v148f p7601 is not supported
[    9.931976] usb 2-1: New USB device found, idVendor=148f, idProduct=7601
[    9.931994] usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[   10.077532] rtusb init rt2870 --->
[   10.079338] 

=== pAd = e0c58000, size = 860808 ===

[   10.079939] ERROR: 256 KiB atomic DMA coherent pool is too small!
Please increase it with coherent_pool= kernel parameter!
[   10.079968] <-- ERROR in Alloc Bulk buffer for HTTxContext!
[   10.079983] ---> RTMPFreeTxRxRingMemory
[   10.080026] <--- RTMPFreeTxRxRingMemory
[   10.080040] ERROR!!! Failed to allocate memory - TxRxRing


But 

cat /proc/cmdline 

shows:

console=tty1 root=/dev/mmcblk0p2 ro rootfstype=ext4 rootwait fixrtc capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN,BB-BONE-EMMC-2G,coherent_pool=2M

(this is an embedded device, thats why there are the other parameters
around...)

I do not find any way to set this parameter while compiling the
kernel. And setting the kernel parameter seems not to work either...

Lost?

...or am I only blind... ? ;)

How can I increase the cohorent pool size successfully?

Best regards,
mcc

PS: The driver sources are not included in the kernel and have to be
compiled externally/extra...