Re: [PATCH] mmc: dw_mmc: handle data blocks > than 4kB if IDMAC is used

[Jaehoon Chung]

Hi, Alexey.

On 06/25/2015 05:25 PM, Alexey Brodkin wrote:
> As per DW MobileStorage databook "each descriptor can transfer up to 4kB
> of data in chained mode", moreover buffer size that is put in "des1" is
> limited to 13 bits, i.e. for example on attempt to
> IDMAC_SET_BUFFER1_SIZE(desc, 8192) size value that's effectively written
> will be 0.
> 
> On the platform with 8kB PAGE_SIZE I see dw_mmc gets data blocks in
> SG-list of 8kB size and that leads to unpredictable behavior of the
> SD/MMC controller.

I didn't see your problem, since i didn't test with 8K PAGE_SIZE.
But I think your patch is reasonable.
As possible, I want to know in more detail what unpredictable behavior.
(Just stuck behavior?)

> 
> In particular on write to FAT partition of SD-card the controller will
> stuck in the middle of DMA transaction.
> 
> Solution to the problem is simple - we need to pass large (> 4kB) data
> buffers to the controller via multiple descriptors. And that's what
> that change does.
> 
> What's interesting I did try original driver on same platform but
> configured with 4kB PAGE_SIZE and may confirm that data blocks passed
> in SG-list to dw_mmc never exeed 4kB limit - that explains why nobody
> ever faced a problem I did.
> 
> Signed-off-by: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
> Cc: Seungwon Jeon <tgih.jun@xxxxxxxxxxx>
> Cc: Jaehoon Chung <jh80.chung@xxxxxxxxxxx>
> Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> Cc: arc-linux-dev@xxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
>  drivers/mmc/host/dw_mmc.c | 109 ++++++++++++++++++++++++++++++----------------
>  1 file changed, 71 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 40e9d8e..e41fb74 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -99,6 +99,9 @@ struct idmac_desc {
>  
>  	__le32		des3;	/* buffer 2 physical address */
>  };
> +
> +/* Each descriptor can transfer up to 4KB of data in chained mode */
> +#define DW_MCI_DESC_DATA_LENGTH	0x1000
>  #endif /* CONFIG_MMC_DW_IDMAC */
>  
>  static bool dw_mci_reset(struct dw_mci *host);
> @@ -462,66 +465,96 @@ static void dw_mci_idmac_complete_dma(struct dw_mci *host)
>  static void dw_mci_translate_sglist(struct dw_mci *host, struct mmc_data *data,
>  				    unsigned int sg_len)
>  {
> +	unsigned int desc_len;
>  	int i;
>  	if (host->dma_64bit_address == 1) {
> -		struct idmac_desc_64addr *desc = host->sg_cpu;
> +		struct idmac_desc_64addr *desc_first, *desc_last, *desc;

Why it needs desc_first?

> +
> +		desc_first = desc_last = desc = host->sg_cpu;
>  
> -		for (i = 0; i < sg_len; i++, desc++) {
> +		for (i = 0; i < sg_len; i++) {
>  			unsigned int length = sg_dma_len(&data->sg[i]);
>  			u64 mem_addr = sg_dma_address(&data->sg[i]);
>  
> -			/*
> -			 * Set the OWN bit and disable interrupts for this
> -			 * descriptor
> -			 */
> -			desc->des0 = IDMAC_DES0_OWN | IDMAC_DES0_DIC |
> -						IDMAC_DES0_CH;
> -			/* Buffer length */
> -			IDMAC_64ADDR_SET_BUFFER1_SIZE(desc, length);
> -
> -			/* Physical address to DMA to/from */
> -			desc->des4 = mem_addr & 0xffffffff;
> -			desc->des5 = mem_addr >> 32;
> +			for ( ; length ; desc++) {

Is there no infinite loop case?

Best Regards,
Jaehoon Chung

> +				desc_len = (length <= DW_MCI_DESC_DATA_LENGTH) ?
> +					   length : DW_MCI_DESC_DATA_LENGTH;
> +
> +				length -= desc_len;
> +
> +				/*
> +				 * Set the OWN bit and disable interrupts
> +				 * for this descriptor
> +				 */
> +				desc->des0 = IDMAC_DES0_OWN | IDMAC_DES0_DIC |
> +							IDMAC_DES0_CH;
> +
> +				/* Buffer length */
> +				IDMAC_64ADDR_SET_BUFFER1_SIZE(desc, desc_len);
> +
> +				/* Physical address to DMA to/from */
> +				desc->des4 = mem_addr & 0xffffffff;
> +				desc->des5 = mem_addr >> 32;
> +
> +				/* Update physical address for the next desc */
> +				mem_addr += desc_len;
> +
> +				/* Save pointer to the last descriptor */
> +				desc_last = desc;
> +			}
>  		}
>  
>  		/* Set first descriptor */
> -		desc = host->sg_cpu;
> -		desc->des0 |= IDMAC_DES0_FD;
> +		desc_first->des0 |= IDMAC_DES0_FD;
>  
>  		/* Set last descriptor */
> -		desc = host->sg_cpu + (i - 1) *
> -				sizeof(struct idmac_desc_64addr);
> -		desc->des0 &= ~(IDMAC_DES0_CH | IDMAC_DES0_DIC);
> -		desc->des0 |= IDMAC_DES0_LD;
> +		desc_last->des0 &= ~(IDMAC_DES0_CH | IDMAC_DES0_DIC);
> +		desc_last->des0 |= IDMAC_DES0_LD;
>  
>  	} else {
> -		struct idmac_desc *desc = host->sg_cpu;
> +		struct idmac_desc *desc_first, *desc_last, *desc;
> +
> +		desc_first = desc_last = desc = host->sg_cpu;
>  
> -		for (i = 0; i < sg_len; i++, desc++) {
> +		for (i = 0; i < sg_len; i++) {
>  			unsigned int length = sg_dma_len(&data->sg[i]);
>  			u32 mem_addr = sg_dma_address(&data->sg[i]);
>  
> -			/*
> -			 * Set the OWN bit and disable interrupts for this
> -			 * descriptor
> -			 */
> -			desc->des0 = cpu_to_le32(IDMAC_DES0_OWN |
> -					IDMAC_DES0_DIC | IDMAC_DES0_CH);
> -			/* Buffer length */
> -			IDMAC_SET_BUFFER1_SIZE(desc, length);
> +			for ( ; length ; desc++) {
> +				desc_len = (length <= DW_MCI_DESC_DATA_LENGTH) ?
> +					   length : DW_MCI_DESC_DATA_LENGTH;
> +
> +				length -= desc_len;
> +
> +				/*
> +				 * Set the OWN bit and disable interrupts
> +				 * for this descriptor
> +				 */
> +				desc->des0 = cpu_to_le32(IDMAC_DES0_OWN |
> +							 IDMAC_DES0_DIC |
> +							 IDMAC_DES0_CH);
> +
> +				/* Buffer length */
> +				IDMAC_SET_BUFFER1_SIZE(desc, desc_len);
>  
> -			/* Physical address to DMA to/from */
> -			desc->des2 = cpu_to_le32(mem_addr);
> +				/* Physical address to DMA to/from */
> +				desc->des2 = cpu_to_le32(mem_addr);
> +
> +				/* Update physical address for the next desc */
> +				mem_addr += desc_len;
> +
> +				/* Save pointer to the last descriptor */
> +				desc_last = desc;
> +			}
>  		}
>  
>  		/* Set first descriptor */
> -		desc = host->sg_cpu;
> -		desc->des0 |= cpu_to_le32(IDMAC_DES0_FD);
> +		desc_first->des0 |= cpu_to_le32(IDMAC_DES0_FD);
>  
>  		/* Set last descriptor */
> -		desc = host->sg_cpu + (i - 1) * sizeof(struct idmac_desc);
> -		desc->des0 &= cpu_to_le32(~(IDMAC_DES0_CH | IDMAC_DES0_DIC));
> -		desc->des0 |= cpu_to_le32(IDMAC_DES0_LD);
> +		desc_last->des0 &= cpu_to_le32(~(IDMAC_DES0_CH |
> +					       IDMAC_DES0_DIC));
> +		desc_last->des0 |= cpu_to_le32(IDMAC_DES0_LD);
>  	}
>  
>  	wmb();
> @@ -2394,7 +2427,7 @@ static int dw_mci_init_slot(struct dw_mci *host, unsigned int id)
>  #ifdef CONFIG_MMC_DW_IDMAC
>  		mmc->max_segs = host->ring_size;
>  		mmc->max_blk_size = 65536;
> -		mmc->max_seg_size = 0x1000;
> +		mmc->max_seg_size = DW_MCI_DESC_DATA_LENGTH;
>  		mmc->max_req_size = mmc->max_seg_size * host->ring_size;
>  		mmc->max_blk_count = mmc->max_req_size / 512;
>  #else
> 

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