Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751841AbdCPKhu (ORCPT ); Thu, 16 Mar 2017 06:37:50 -0400 Received: from hqemgate15.nvidia.com ([216.228.121.64]:18008 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751182AbdCPKhp (ORCPT ); Thu, 16 Mar 2017 06:37:45 -0400 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 16 Mar 2017 03:37:19 -0700 From: Jon Hunter To: Adrian Hunter , Ulf Hansson , Thierry Reding , Ritesh Harjani CC: , , , Jon Hunter Subject: [PATCH 1/2] mmc: sdhci: Add support for setting parent clock Date: Thu, 16 Mar 2017 10:32:43 +0000 Message-ID: <1489660364-17698-1-git-send-email-jonathanh@nvidia.com> X-Mailer: git-send-email 2.7.4 X-NVConfidentiality: public MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2312 Lines: 57 It is common for SD/MMC host controllers to set the parent clock that drives the SD/MMC interface in order to support various operating speeds. Typically, this is performed by calling common clock framework APIs such as clk_set_rate(). The problem is that these APIs may sleep and must not be called from within atomic sections and therefore, these functions cannot be called within the existing 'set_clock' SDHCI operator because they are called from within the context of a spinlock. Add a new 'set_parent_clock' operator for the SDHCI driver that is called early during the SDHCI 'set_ios' before the spinlock is aquire to give the platform driver the opportunity to set the parent clock rate. Please note that, unfortunately, the Tegra and MSM SDHCI drivers currently appear to mis-use the 'set_clock' operator by calling clk_set_rate(). In the case of Tegra, occasionally but not always, 'scheduling while atomic' errors are reported (so most of the time we are getting lucky). In the of the MSM SDHCI driver, it is releasing and re-acquiring the spinlock which is bad. Signed-off-by: Jon Hunter --- I have not attempted to fix the MSM driver in this seris, but I am copying hopefully, the right people to fix it. drivers/mmc/host/sdhci.c | 3 +++ drivers/mmc/host/sdhci.h | 2 ++ 2 files changed, 5 insertions(+) diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index 6fdd7a70f229..b7f1521edbec 100644 --- a/drivers/mmc/host/sdhci.c +++ b/drivers/mmc/host/sdhci.c @@ -1579,6 +1579,9 @@ static void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios) if (ios->power_mode == MMC_POWER_UNDEFINED) return; + if (host->ops->set_parent_clock) + host->ops->set_parent_clock(host, ios->power_mode); + spin_lock_irqsave(&host->lock, flags); if (host->flags & SDHCI_DEVICE_DEAD) { diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h index edf3adfbc213..585fbcdab70c 100644 --- a/drivers/mmc/host/sdhci.h +++ b/drivers/mmc/host/sdhci.h @@ -541,6 +541,8 @@ struct sdhci_ops { #endif void (*set_clock)(struct sdhci_host *host, unsigned int clock); + void (*set_parent_clock)(struct sdhci_host *host, + unsigned int clock); void (*set_power)(struct sdhci_host *host, unsigned char mode, unsigned short vdd); -- 2.7.4