Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757078AbaD2IU2 (ORCPT ); Tue, 29 Apr 2014 04:20:28 -0400 Received: from mail-wg0-f43.google.com ([74.125.82.43]:42098 "EHLO mail-wg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757038AbaD2IUX (ORCPT ); Tue, 29 Apr 2014 04:20:23 -0400 From: srinivas.kandagatla@linaro.org To: Russell King , linux-mmc@vger.kernel.org Cc: Chris Ball , Ulf Hansson , linux-kernel@vger.kernel.org, agross@quicinc.com, linux-arm-msm@vger.kernel.org, Srinivas Kandagatla Subject: [PATCH v1 06/11] mmc: mmci: Qcomm: Add 3 clock cycle delay after register write Date: Tue, 29 Apr 2014 09:20:14 +0100 Message-Id: <1398759614-13217-1-git-send-email-srinivas.kandagatla@linaro.org> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1398759492-12970-1-git-send-email-srinivas.kandagatla@linaro.org> References: <1398759492-12970-1-git-send-email-srinivas.kandagatla@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Srinivas Kandagatla Most of the Qcomm SD card controller registers must be updated to the MCLK domain so subsequent writes to registers will be ignored until 3 clock cycles have passed. This patch adds a 3 clock cycle delay required after writing to controller registers on Qualcomm SOCs. Without this delay all the register writes are not successfull, resulting in not detecting cards. Signed-off-by: Srinivas Kandagatla --- drivers/mmc/host/mmci.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c index 4f8d0ba..f73dc48 100644 --- a/drivers/mmc/host/mmci.c +++ b/drivers/mmc/host/mmci.c @@ -179,6 +179,14 @@ static inline u32 mmci_readl(struct mmci_host *host, u32 off) static inline void mmci_writel(struct mmci_host *host, u32 data, u32 off) { writel(data, host->base + off); + + /* + * On QCom SD card controller, registers must be updated to the + * MCLK domain so subsequent writes to this register will be ignored + * for 3 clk cycles. + */ + if (host->hw_designer == AMBA_VENDOR_QCOM) + udelay(1 + ((3 * USEC_PER_SEC)/host->mclk)); } static int mmci_card_busy(struct mmc_host *mmc) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/