From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Shtylyov Subject: Re: [RFC/RFT PATCH 3/5] scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations Date: Sat, 13 Jul 2013 03:42:55 +0400 Message-ID: <51E0947F.1040800@cogentembedded.com> References: <1373665694-7580-1-git-send-email-santosh.shilimkar@ti.com> <1373665694-7580-4-git-send-email-santosh.shilimkar@ti.com> <51E07B6E.5090900@cogentembedded.com> <20130712222506.GI24642@n2100.arm.linux.org.uk> <51E08C6B.2080802@cogentembedded.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-la0-f44.google.com ([209.85.215.44]:53130 "EHLO mail-la0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756436Ab3GLXnC (ORCPT ); Fri, 12 Jul 2013 19:43:02 -0400 Received: by mail-la0-f44.google.com with SMTP id er20so8172031lab.3 for ; Fri, 12 Jul 2013 16:43:00 -0700 (PDT) In-Reply-To: <51E08C6B.2080802@cogentembedded.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Russell King - ARM Linux Cc: Santosh Shilimkar , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-scsi@vger.kernel.org On 07/13/2013 03:08 AM, Sergei Shtylyov wrote: >>>> DMA bounce limit is the maximum direct DMA'able memory beyond which >>>> bounce buffers has to be used to perform dma operations. SCSI driver >>>> relies on dma_mask but its calculation is based on max_*pfn which >>>> don't have uniform meaning across architectures. So make use of >>>> dma_max_pfn() which is expected to return the DMAable maximum pfn >>>> value across architectures. >>>> Cc: Russell King >>>> Cc: linux-scsi@vger.kernel.org >>>> Signed-off-by: Santosh Shilimkar >>>> --- >>>> drivers/scsi/scsi_lib.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c >>>> index 86d5220..e8275fa 100644 >>>> --- a/drivers/scsi/scsi_lib.c >>>> +++ b/drivers/scsi/scsi_lib.c >>>> @@ -1668,7 +1668,7 @@ u64 scsi_calculate_bounce_limit(struct >>>> Scsi_Host *shost) >>>> >>>> host_dev = scsi_get_device(shost); >>>> if (host_dev && host_dev->dma_mask) >>>> - bounce_limit = *host_dev->dma_mask; >>>> + bounce_limit = dma_max_pfn(host_dev) << PAGE_SHIFT; >>> You definitely forgot -1 here. >> Please explain your point. > Previously, 'bounce_limit' would look like 0xffffffff (unless I'm > mistaken), now it would look like 0xfffff000 which is hardly what we're > looking for, no? Although, -1 won't give us the correct result in this case, it's more like + PAGE_SIZE - 1. WBR, Sergei