From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Ujfalusi Subject: [PATCH v2 1/2] OMAP2+: DMA: Workaround for invalid source position Date: Mon, 7 Nov 2011 11:33:06 +0200 Message-ID: <1320658387-21067-2-git-send-email-peter.ujfalusi@ti.com> References: <1320658387-21067-1-git-send-email-peter.ujfalusi@ti.com> Return-path: Received: from na3sys009aog114.obsmtp.com ([74.125.149.211]:42112 "EHLO na3sys009aog114.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751894Ab1KGJdZ (ORCPT ); Mon, 7 Nov 2011 04:33:25 -0500 Received: by bke11 with SMTP id 11so4540987bke.5 for ; Mon, 07 Nov 2011 01:33:23 -0800 (PST) In-Reply-To: <1320658387-21067-1-git-send-email-peter.ujfalusi@ti.com> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Tony Lindgren Cc: Jarkko Nikula , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org If the DMA source position has been asked before the first actual data transfer has been done, the CSAC register does not contain valid information. We can identify this situation by checking the CDAC register: CDAC != 0 indicates that the DMA transfer on the channel has been started already. When CDAC == 0 we can not trust the CSAC value since it has not been updated, and can contain random number. Return the start address in case the DMA has not jet started. Note: The CDAC register has been initialized to 0 at dma_start time. Signed-off-by: Peter Ujfalusi --- arch/arm/plat-omap/dma.c | 12 ++++++++++++ 1 files changed, 12 insertions(+), 0 deletions(-) diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c index c22217c..a9983b6 100644 --- a/arch/arm/plat-omap/dma.c +++ b/arch/arm/plat-omap/dma.c @@ -1034,6 +1034,18 @@ dma_addr_t omap_get_dma_src_pos(int lch) if (IS_DMA_ERRATA(DMA_ERRATA_3_3) && offset == 0) offset = p->dma_read(CSAC, lch); + if (!cpu_is_omap15xx()) { + /* + * CDAC == 0 indicates that the DMA transfer on the channel has + * not been started (no data has been transferred so far). + * Return the programmed source start address in this case. + */ + if (likely(p->dma_read(CDAC, lch))) + offset = p->dma_read(CSAC, lch); + else + offset = p->dma_read(CSSA, lch); + } + if (cpu_class_is_omap1()) offset |= (p->dma_read(CSSA, lch) & 0xFFFF0000); -- 1.7.7.2