[PATCH v2 2/4] mmc: dw_mmc: avoid race condition of cpu and IDMAC
Jaehoon Chung
jh80.chung at samsung.com
Wed Sep 21 21:26:19 PDT 2016
On 09/02/2016 01:14 PM, Shawn Lin wrote:
> We could see an obvious race condition by test that
> the former write operation by IDMAC aiming to clear
> OWN bit reach right after the later configuration of
> the same desc, which makes the IDMAC be in SUSPEND
> state as the OWN bit was cleared by the asynchronous
> write operation of IDMAC. The bug can be very easy
> reproduced on RK3288 or similar when we reduce the
> running rate of system buses and keep the CPU running
> faster. So as two separate masters, IDMAC and cpu
> write the same descriptor stored on the same address,
> and this should be protected by adding check of OWN
> bit before preparing new descriptors.
Applied on my tree. Thanks!
Best Regards,
Jaehoon Chung
>
> Signed-off-by: Shawn Lin <shawn.lin at rock-chips.com>
>
> ---
>
> Changes in v2:
> - fallback to PIO mode if failing to wait for OWN bit
> - cleanup polluted desc chain as the own bit error could
> occur on any place of the chain, so we need to clr the desc
> configured before that one. Use the exist function to reinit
> the desc chain. As this issue is really rare, so after applied,
> the fio/iozone stress test didn't show up performance regression.
>
> drivers/mmc/host/dw_mmc.c | 208 ++++++++++++++++++++++++++++------------------
> 1 file changed, 129 insertions(+), 79 deletions(-)
>
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 782b303..daa1c52 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -467,12 +467,87 @@ static void dw_mci_dmac_complete_dma(void *arg)
> }
> }
>
> -static inline void dw_mci_prepare_desc64(struct dw_mci *host,
> +static int dw_mci_idmac_init(struct dw_mci *host)
> +{
> + int i;
> +
> + if (host->dma_64bit_address == 1) {
> + struct idmac_desc_64addr *p;
> + /* Number of descriptors in the ring buffer */
> + host->ring_size = PAGE_SIZE / sizeof(struct idmac_desc_64addr);
> +
> + /* Forward link the descriptor list */
> + for (i = 0, p = host->sg_cpu; i < host->ring_size - 1;
> + i++, p++) {
> + p->des6 = (host->sg_dma +
> + (sizeof(struct idmac_desc_64addr) *
> + (i + 1))) & 0xffffffff;
> +
> + p->des7 = (u64)(host->sg_dma +
> + (sizeof(struct idmac_desc_64addr) *
> + (i + 1))) >> 32;
> + /* Initialize reserved and buffer size fields to "0" */
> + p->des1 = 0;
> + p->des2 = 0;
> + p->des3 = 0;
> + }
> +
> + /* Set the last descriptor as the end-of-ring descriptor */
> + p->des6 = host->sg_dma & 0xffffffff;
> + p->des7 = (u64)host->sg_dma >> 32;
> + p->des0 = IDMAC_DES0_ER;
> +
> + } else {
> + struct idmac_desc *p;
> + /* Number of descriptors in the ring buffer */
> + host->ring_size = PAGE_SIZE / sizeof(struct idmac_desc);
> +
> + /* Forward link the descriptor list */
> + for (i = 0, p = host->sg_cpu;
> + i < host->ring_size - 1;
> + i++, p++) {
> + p->des3 = cpu_to_le32(host->sg_dma +
> + (sizeof(struct idmac_desc) * (i + 1)));
> + p->des1 = 0;
> + }
> +
> + /* Set the last descriptor as the end-of-ring descriptor */
> + p->des3 = cpu_to_le32(host->sg_dma);
> + p->des0 = cpu_to_le32(IDMAC_DES0_ER);
> + }
> +
> + dw_mci_idmac_reset(host);
> +
> + if (host->dma_64bit_address == 1) {
> + /* Mask out interrupts - get Tx & Rx complete only */
> + mci_writel(host, IDSTS64, IDMAC_INT_CLR);
> + mci_writel(host, IDINTEN64, SDMMC_IDMAC_INT_NI |
> + SDMMC_IDMAC_INT_RI | SDMMC_IDMAC_INT_TI);
> +
> + /* Set the descriptor base address */
> + mci_writel(host, DBADDRL, host->sg_dma & 0xffffffff);
> + mci_writel(host, DBADDRU, (u64)host->sg_dma >> 32);
> +
> + } else {
> + /* Mask out interrupts - get Tx & Rx complete only */
> + mci_writel(host, IDSTS, IDMAC_INT_CLR);
> + mci_writel(host, IDINTEN, SDMMC_IDMAC_INT_NI |
> + SDMMC_IDMAC_INT_RI | SDMMC_IDMAC_INT_TI);
> +
> + /* Set the descriptor base address */
> + mci_writel(host, DBADDR, host->sg_dma);
> + }
> +
> + return 0;
> +}
> +
> +static inline int dw_mci_prepare_desc64(struct dw_mci *host,
> struct mmc_data *data,
> unsigned int sg_len)
> {
> unsigned int desc_len;
> struct idmac_desc_64addr *desc_first, *desc_last, *desc;
> + unsigned long timeout;
> int i;
>
> desc_first = desc_last = desc = host->sg_cpu;
> @@ -489,6 +564,19 @@ static inline void dw_mci_prepare_desc64(struct dw_mci *host,
> length -= desc_len;
>
> /*
> + * Wait for the former clear OWN bit operation
> + * of IDMAC to make sure that this descriptor
> + * isn't still owned by IDMAC as IDMAC's write
> + * ops and CPU's read ops are asynchronous.
> + */
> + timeout = jiffies + msecs_to_jiffies(100);
> + while (readl(&desc->des0) & IDMAC_DES0_OWN) {
> + if (time_after(jiffies, timeout))
> + goto err_own_bit;
> + udelay(10);
> + }
> +
> + /*
> * Set the OWN bit and disable interrupts
> * for this descriptor
> */
> @@ -516,15 +604,24 @@ static inline void dw_mci_prepare_desc64(struct dw_mci *host,
> /* Set last descriptor */
> desc_last->des0 &= ~(IDMAC_DES0_CH | IDMAC_DES0_DIC);
> desc_last->des0 |= IDMAC_DES0_LD;
> +
> + return 0;
> +err_own_bit:
> + /* restore the descriptor chain as it's polluted */
> + dev_dbg(host->dev, "desciptor is still owned by IDMAC.\n");
> + memset(host->sg_cpu, 0, PAGE_SIZE);
> + dw_mci_idmac_init(host);
> + return -EINVAL;
> }
>
>
> -static inline void dw_mci_prepare_desc32(struct dw_mci *host,
> +static inline int dw_mci_prepare_desc32(struct dw_mci *host,
> struct mmc_data *data,
> unsigned int sg_len)
> {
> unsigned int desc_len;
> struct idmac_desc *desc_first, *desc_last, *desc;
> + unsigned long timeout;
> int i;
>
> desc_first = desc_last = desc = host->sg_cpu;
> @@ -541,6 +638,20 @@ static inline void dw_mci_prepare_desc32(struct dw_mci *host,
> length -= desc_len;
>
> /*
> + * Wait for the former clear OWN bit operation
> + * of IDMAC to make sure that this descriptor
> + * isn't still owned by IDMAC as IDMAC's write
> + * ops and CPU's read ops are asynchronous.
> + */
> + timeout = jiffies + msecs_to_jiffies(100);
> + while (readl(&desc->des0) &
> + cpu_to_le32(IDMAC_DES0_OWN)) {
> + if (time_after(jiffies, timeout))
> + goto err_own_bit;
> + udelay(10);
> + }
> +
> + /*
> * Set the OWN bit and disable interrupts
> * for this descriptor
> */
> @@ -569,16 +680,28 @@ static inline void dw_mci_prepare_desc32(struct dw_mci *host,
> desc_last->des0 &= cpu_to_le32(~(IDMAC_DES0_CH |
> IDMAC_DES0_DIC));
> desc_last->des0 |= cpu_to_le32(IDMAC_DES0_LD);
> +
> + return 0;
> +err_own_bit:
> + /* restore the descriptor chain as it's polluted */
> + dev_dbg(host->dev, "desciptor is still owned by IDMAC.\n");
> + memset(host->sg_cpu, 0, PAGE_SIZE);
> + dw_mci_idmac_init(host);
> + return -EINVAL;
> }
>
> static int dw_mci_idmac_start_dma(struct dw_mci *host, unsigned int sg_len)
> {
> u32 temp;
> + int ret;
>
> if (host->dma_64bit_address == 1)
> - dw_mci_prepare_desc64(host, host->data, sg_len);
> + ret = dw_mci_prepare_desc64(host, host->data, sg_len);
> else
> - dw_mci_prepare_desc32(host, host->data, sg_len);
> + ret = dw_mci_prepare_desc32(host, host->data, sg_len);
> +
> + if (ret)
> + goto out;
>
> /* drain writebuffer */
> wmb();
> @@ -603,81 +726,8 @@ static int dw_mci_idmac_start_dma(struct dw_mci *host, unsigned int sg_len)
> /* Start it running */
> mci_writel(host, PLDMND, 1);
>
> - return 0;
> -}
> -
> -static int dw_mci_idmac_init(struct dw_mci *host)
> -{
> - int i;
> -
> - if (host->dma_64bit_address == 1) {
> - struct idmac_desc_64addr *p;
> - /* Number of descriptors in the ring buffer */
> - host->ring_size = PAGE_SIZE / sizeof(struct idmac_desc_64addr);
> -
> - /* Forward link the descriptor list */
> - for (i = 0, p = host->sg_cpu; i < host->ring_size - 1;
> - i++, p++) {
> - p->des6 = (host->sg_dma +
> - (sizeof(struct idmac_desc_64addr) *
> - (i + 1))) & 0xffffffff;
> -
> - p->des7 = (u64)(host->sg_dma +
> - (sizeof(struct idmac_desc_64addr) *
> - (i + 1))) >> 32;
> - /* Initialize reserved and buffer size fields to "0" */
> - p->des1 = 0;
> - p->des2 = 0;
> - p->des3 = 0;
> - }
> -
> - /* Set the last descriptor as the end-of-ring descriptor */
> - p->des6 = host->sg_dma & 0xffffffff;
> - p->des7 = (u64)host->sg_dma >> 32;
> - p->des0 = IDMAC_DES0_ER;
> -
> - } else {
> - struct idmac_desc *p;
> - /* Number of descriptors in the ring buffer */
> - host->ring_size = PAGE_SIZE / sizeof(struct idmac_desc);
> -
> - /* Forward link the descriptor list */
> - for (i = 0, p = host->sg_cpu;
> - i < host->ring_size - 1;
> - i++, p++) {
> - p->des3 = cpu_to_le32(host->sg_dma +
> - (sizeof(struct idmac_desc) * (i + 1)));
> - p->des1 = 0;
> - }
> -
> - /* Set the last descriptor as the end-of-ring descriptor */
> - p->des3 = cpu_to_le32(host->sg_dma);
> - p->des0 = cpu_to_le32(IDMAC_DES0_ER);
> - }
> -
> - dw_mci_idmac_reset(host);
> -
> - if (host->dma_64bit_address == 1) {
> - /* Mask out interrupts - get Tx & Rx complete only */
> - mci_writel(host, IDSTS64, IDMAC_INT_CLR);
> - mci_writel(host, IDINTEN64, SDMMC_IDMAC_INT_NI |
> - SDMMC_IDMAC_INT_RI | SDMMC_IDMAC_INT_TI);
> -
> - /* Set the descriptor base address */
> - mci_writel(host, DBADDRL, host->sg_dma & 0xffffffff);
> - mci_writel(host, DBADDRU, (u64)host->sg_dma >> 32);
> -
> - } else {
> - /* Mask out interrupts - get Tx & Rx complete only */
> - mci_writel(host, IDSTS, IDMAC_INT_CLR);
> - mci_writel(host, IDINTEN, SDMMC_IDMAC_INT_NI |
> - SDMMC_IDMAC_INT_RI | SDMMC_IDMAC_INT_TI);
> -
> - /* Set the descriptor base address */
> - mci_writel(host, DBADDR, host->sg_dma);
> - }
> -
> - return 0;
> +out:
> + return ret;
> }
>
> static const struct dw_mci_dma_ops dw_mci_idmac_ops = {
>
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