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Message-id: <d3cd8993-7c5e-bdd4-5182-aec5fd0b040c@samsung.com>
Date: Tue, 20 Sep 2016 18:49:22 +0900
From: Jaehoon Chung <jh80.chung@...sung.com>
To: Shawn Lin <shawn.lin@...k-chips.com>
Cc: Ulf Hansson <ulf.hansson@...aro.org>, linux-mmc@...r.kernel.org,
linux-kernel@...r.kernel.org,
Doug Anderson <dianders@...omium.org>,
Heiko Stuebner <heiko@...ech.de>,
linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v2 2/4] mmc: dw_mmc: avoid race condition of cpu and IDMAC
Hi Shawn,
On 09/20/2016 06:47 PM, Shawn Lin wrote:
> Hi Jaehoon,
>
> Friendly ping... :)
Thanks for reminding! :) I forgot your patch-set..sorry!
Best Regards,
Jaehoon Chung
>
> On 2016/9/2 12:14, 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.
>>
>> Signed-off-by: Shawn Lin <shawn.lin@...k-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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