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Date: Wed, 2 Dec 2015 14:56:57 +0200 From: Stanimir Varbanov <stanimir.varbanov@...aro.org> To: Arnd Bergmann <arnd@...db.de>, linux-arm-kernel@...ts.infradead.org Cc: linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, dmaengine@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>, Mark Rutland <mark.rutland@....com>, Archit Taneja <architt@...eaurora.org>, Pawel Moll <pawel.moll@....com>, Ian Campbell <ijc+devicetree@...lion.org.uk>, Rob Herring <robh+dt@...nel.org>, Andy Gross <agross@...eaurora.org> Subject: Re: [PATCH 2/4] dmaengine: qcom_bam_dma: clear BAM interrupt only if it is rised On 12/01/2015 12:29 PM, Arnd Bergmann wrote: > On Tuesday 01 December 2015 11:14:57 Stanimir Varbanov wrote: >> + if (srcs & BAM_IRQ) { >> clr_mask = readl_relaxed(bam_addr(bdev, 0, BAM_IRQ_STTS)); >> >> - /* don't allow reorder of the various accesses to the BAM registers */ >> - mb(); >> + /* >> + * don't allow reorder of the various accesses to the BAM >> + * registers >> + */ >> + mb(); >> >> - writel_relaxed(clr_mask, bam_addr(bdev, 0, BAM_IRQ_CLR)); >> + writel_relaxed(clr_mask, bam_addr(bdev, 0, BAM_IRQ_CLR)); >> + } >> > > I think the comment here should be moved: change the writel_relaxed() > to writel(), which already includes the appropriate barriers, and If we agree with such a change it should be subject to another patch. > add a comment at the readl_relaxed() to explain why it doesn't need > a barrier. Infact I'm not sure that readl_relaxed(BAM_IRQ_STTS) does not need barrier. If I read the code above correctly the mb() should guarantee that all load and store operations before it are happened before the write to BAM_IRQ_CLR register, and on the other hand if we replace writel_relaxed with writel, the writel has wmb() which guarantees only store operations. Did I miss something? -- regards, Stan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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