From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (bilbo.ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 42GsbG3hWgzF3QF for ; Fri, 21 Sep 2018 21:59:38 +1000 (AEST) In-Reply-To: <20180911053805.5345-1-aik@ozlabs.ru> To: Alexey Kardashevskiy , linuxppc-dev@lists.ozlabs.org From: Michael Ellerman Cc: Alexey Kardashevskiy Subject: Re: [kernel] powerpc/powernv/ioda2: Reduce upper limit for DMA window size (retry) Message-Id: <42GsbG2KQHz9sCV@ozlabs.org> Date: Fri, 21 Sep 2018 21:59:38 +1000 (AEST) List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 2018-09-11 at 05:38:05 UTC, Alexey Kardashevskiy wrote: > We use PHB in mode1 which uses bit 59 to select a correct DMA window. > However there is mode2 which uses bits 59:55 and allows up to 32 DMA > windows per a PE. > > Even though documentation does not clearly specify that, it seems that > the actual hardware does not support bits 59:55 even in mode1, in other > words we can create a window as big as 1<<58 but DMA simply won't work. > > This reduces the upper limit from 59 to 55 bits to let the userspace know > about the hardware limits. > > Fixes: ce57c6610cc2 "Merge branch 'topic/ppc-kvm' into next" > Signed-off-by: Alexey Kardashevskiy Applied to powerpc fixes, thanks. https://git.kernel.org/powerpc/c/7233b8cab39014620ac9534da11f0f cheers