From mboxrd@z Thu Jan 1 00:00:00 1970 From: Doug Anderson Subject: [PATCH v5 4/4] mmc: dw_mmc: Protect read-modify-write of INTMASK with a lock Date: Tue, 2 Dec 2014 15:42:47 -0800 Message-ID: <1417563767-32181-5-git-send-email-dianders@chromium.org> References: <1417563767-32181-1-git-send-email-dianders@chromium.org> Return-path: In-Reply-To: <1417563767-32181-1-git-send-email-dianders@chromium.org> Sender: linux-kernel-owner@vger.kernel.org To: Jaehoon Chung , Seungwon Jeon , Ulf Hansson Cc: Alim Akhtar , Sonny Rao , Andrew Bresticker , Heiko Stuebner , Doug Anderson , chris@printf.net, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-mmc@vger.kernel.org We're running into cases where our enabling of the SDIO interrupt in dw_mmc doesn't actually take effect. Specifically, adding patch like this: +++ b/drivers/mmc/host/dw_mmc.c @@ -1076,6 +1076,9 @@ static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb) mci_writel(host, INTMASK, (int_mask | SDMMC_INT_SDIO(slot->id))); + int_mask = mci_readl(host, INTMASK); + if (!(int_mask & SDMMC_INT_SDIO(slot->id))) + dev_err(&mmc->class_dev, "failed to enable sdio irq\n"); } else { ...actually triggers the error message. That's because the dw_mci_enable_sdio_irq() unsafely does a read-modify-write of the INTMASK register. We can't just use the standard host->lock since that lock is not irq safe and mmc_signal_sdio_irq() (called from interrupt context) calls dw_mci_enable_sdio_irq(). Add a new irq-safe lock to protect INTMASK. An alternate solution to this is to punt mmc_signal_sdio_irq() to the tasklet and then protect INTMASK modifications by the standard host lock. This seemed like a bit more of a high-latency change. Reported-by: Bing Zhao Signed-off-by: Doug Anderson Reviewed-by: James Hogan --- Changes in v5: None Changes in v3: None Changes in v2: - intmask_lock renamed to irq_lock drivers/mmc/host/dw_mmc.c | 13 +++++++++++++ include/linux/mmc/dw_mmc.h | 6 ++++++ 2 files changed, 19 insertions(+) diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c index ae10a02..64ea042 100644 --- a/drivers/mmc/host/dw_mmc.c +++ b/drivers/mmc/host/dw_mmc.c @@ -759,6 +759,7 @@ disable: static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data) { + unsigned long irqflags; int sg_len; u32 temp; @@ -795,9 +796,11 @@ static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data) mci_writel(host, CTRL, temp); /* Disable RX/TX IRQs, let DMA handle it */ + spin_lock_irqsave(&host->irq_lock, irqflags); temp = mci_readl(host, INTMASK); temp &= ~(SDMMC_INT_RXDR | SDMMC_INT_TXDR); mci_writel(host, INTMASK, temp); + spin_unlock_irqrestore(&host->irq_lock, irqflags); host->dma_ops->start(host, sg_len); @@ -806,6 +809,7 @@ static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data) static void dw_mci_submit_data(struct dw_mci *host, struct mmc_data *data) { + unsigned long irqflags; u32 temp; data->error = -EINPROGRESS; @@ -834,9 +838,12 @@ static void dw_mci_submit_data(struct dw_mci *host, struct mmc_data *data) host->part_buf_count = 0; mci_writel(host, RINTSTS, SDMMC_INT_TXDR | SDMMC_INT_RXDR); + + spin_lock_irqsave(&host->irq_lock, irqflags); temp = mci_readl(host, INTMASK); temp |= SDMMC_INT_TXDR | SDMMC_INT_RXDR; mci_writel(host, INTMASK, temp); + spin_unlock_irqrestore(&host->irq_lock, irqflags); temp = mci_readl(host, CTRL); temp &= ~SDMMC_CTRL_DMA_ENABLE; @@ -1284,8 +1291,11 @@ static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb) { struct dw_mci_slot *slot = mmc_priv(mmc); struct dw_mci *host = slot->host; + unsigned long irqflags; u32 int_mask; + spin_lock_irqsave(&host->irq_lock, irqflags); + /* Enable/disable Slot Specific SDIO interrupt */ int_mask = mci_readl(host, INTMASK); if (enb) @@ -1293,6 +1303,8 @@ static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb) else int_mask &= ~SDMMC_INT_SDIO(slot->sdio_id); mci_writel(host, INTMASK, int_mask); + + spin_unlock_irqrestore(&host->irq_lock, irqflags); } static int dw_mci_execute_tuning(struct mmc_host *mmc, u32 opcode) @@ -2661,6 +2673,7 @@ int dw_mci_probe(struct dw_mci *host) host->quirks = host->pdata->quirks; spin_lock_init(&host->lock); + spin_lock_init(&host->irq_lock); INIT_LIST_HEAD(&host->queue); /* diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h index 42b724e..471fb31 100644 --- a/include/linux/mmc/dw_mmc.h +++ b/include/linux/mmc/dw_mmc.h @@ -106,6 +106,11 @@ struct mmc_data; * @cur_slot, @mrq and @state. These must always be updated * at the same time while holding @lock. * + * @irq_lock is an irq-safe spinlock protecting the INTMASK register + * to allow the interrupt handler to modify it directly. Held for only long + * enough to read-modify-write INTMASK and no other locks are grabbed when + * holding this one. + * * The @mrq field of struct dw_mci_slot is also protected by @lock, * and must always be written at the same time as the slot is added to * @queue. @@ -125,6 +130,7 @@ struct mmc_data; */ struct dw_mci { spinlock_t lock; + spinlock_t irq_lock; void __iomem *regs; struct scatterlist *sg; -- 2.2.0.rc0.207.ga3a616c