[U-Boot] [PATCH 1/2] common: usb_storage : Implement logic to calculate optimal usb maximum trasfer blocks

[Marek Vasut]

On 05/30/2016 01:23 PM, Rajesh Bhagat wrote:
> Implements the logic to calculate the optimal usb maximum trasfer blocks
> instead of sending USB_MAX_XFER_BLK blocks which is 65535 and 20 in case
> of EHCI and other USB protocols respectively.
> 
> It adds an array of trasfer blocks that should be checked for success
> starting from minimum to maximum, and rest of the read/write are
> performed with that optimal value. It tries to increase/decrease the
> blocks in follwing scenarios:
> 
> 1.decrease blocks: when read/write for a particular number of blocks
> fails.
> 2. increase blocks: when read/write for a particular number of blocks
> pass and amount left to trasfer is greater than current number of
> blocks.
> 
> Currently changes are done for EHCI where min = 4096 andmax = 65535
> is taken. And for other cases code is left unchanged by keeping min
> = max = 20.
> 
> Signed-off-by: Sriram Dash <sriram.dash at nxp.com>
> Signed-off-by: Rajesh Bhagat <rajesh.bhagat at nxp.com>
> ---
>  common/usb_storage.c |   54 ++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 43 insertions(+), 11 deletions(-)
> 
> diff --git a/common/usb_storage.c b/common/usb_storage.c
> index 7e6e52d..7b5ad07 100644
> --- a/common/usb_storage.c
> +++ b/common/usb_storage.c
> @@ -101,16 +101,15 @@ struct us_data {
>  };
>  
>  #ifdef CONFIG_USB_EHCI
> -/*
> - * The U-Boot EHCI driver can handle any transfer length as long as there is
> - * enough free heap space left, but the SCSI READ(10) and WRITE(10) commands are
> - * limited to 65535 blocks.
> - */
> -#define USB_MAX_XFER_BLK	65535
> +#define USB_XFER_BLK_TBL_SZ		5
> +static unsigned short usb_xfer_blk_tbl[5] = {4096, 8192, 16384, 32768, 65535};

You should stick to using one block less than the power of two, the
controllers react to that a bit better. Each value in this table can
then be calculated really trivially, it's:

(1 << (12 + n)) - 1

You also don't need such static data.

>  #else
> -#define USB_MAX_XFER_BLK	20
> +#define USB_XFER_BLK_TBL_SZ		1
> +static unsigned short usb_xfer_blk_tbl[1] = {20};
>  #endif
>  
> +static unsigned short USB_MAX_XFER_BLK;

This value is different on per-device basis, how can it be static data ?

>  #ifndef CONFIG_BLK
>  static struct us_data usb_stor[USB_MAX_STOR_DEV];
>  #endif
> @@ -1117,7 +1116,8 @@ static unsigned long usb_stor_read(struct blk_desc *block_dev, lbaint_t blknr,
>  	unsigned short smallblks;
>  	struct usb_device *udev;
>  	struct us_data *ss;
> -	int retry;
> +	int retry, next = LOG2((USB_MAX_XFER_BLK + 1) / usb_xfer_blk_tbl[0]);
> +	bool retry_flag = false;
>  	ccb *srb = &usb_ccb;
>  #ifdef CONFIG_BLK
>  	struct blk_desc *block_dev;
> @@ -1158,6 +1158,8 @@ static unsigned long usb_stor_read(struct blk_desc *block_dev, lbaint_t blknr,
>  		else
>  			smallblks = (unsigned short) blks;
>  retry_it:
> +		debug("usb_read: retry #%d, xfer_blk %hu, smallblks %hu\n",
> +		      retry, USB_MAX_XFER_BLK, smallblks);
>  		if (smallblks == USB_MAX_XFER_BLK)
>  			usb_show_progress();
>  		srb->datalen = block_dev->blksz * smallblks;
> @@ -1165,14 +1167,26 @@ retry_it:
>  		if (usb_read_10(srb, ss, start, smallblks)) {
>  			debug("Read ERROR\n");
>  			usb_request_sense(srb, ss);
> -			if (retry--)
> +			if (retry--) {
> +				/* decrease the USB_MAX_XFER_BLK */
> +				if (next >  0) {
> +					smallblks = usb_xfer_blk_tbl[--next];
> +					USB_MAX_XFER_BLK = smallblks;
> +				}
> +				retry_flag = true;
>  				goto retry_it;
> +			}
>  			blkcnt -= blks;
>  			break;
>  		}
>  		start += smallblks;
>  		blks -= smallblks;
>  		buf_addr += srb->datalen;
> +
> +		/* try to increase the USB_MAX_XFER_BLK */
> +		if (next < USB_XFER_BLK_TBL_SZ  - 1)
> +			if (!retry_flag && usb_xfer_blk_tbl[next + 1] <= blks)
> +				USB_MAX_XFER_BLK = usb_xfer_blk_tbl[++next];
>  	} while (blks != 0);
>  	ss->flags &= ~USB_READY;
>  
> @@ -1199,7 +1213,8 @@ static unsigned long usb_stor_write(struct blk_desc *block_dev, lbaint_t blknr,
>  	unsigned short smallblks;
>  	struct usb_device *udev;
>  	struct us_data *ss;
> -	int retry;
> +	int retry, next = LOG2((USB_MAX_XFER_BLK + 1) / usb_xfer_blk_tbl[0]);
> +	bool retry_flag = false;
>  	ccb *srb = &usb_ccb;
>  #ifdef CONFIG_BLK
>  	struct blk_desc *block_dev;
> @@ -1244,6 +1259,8 @@ static unsigned long usb_stor_write(struct blk_desc *block_dev, lbaint_t blknr,
>  		else
>  			smallblks = (unsigned short) blks;
>  retry_it:
> +		debug("usb_write: retry #%d, xfer_blk %hu, smallblks %hu\n",
> +		      retry, USB_MAX_XFER_BLK, smallblks);
>  		if (smallblks == USB_MAX_XFER_BLK)
>  			usb_show_progress();
>  		srb->datalen = block_dev->blksz * smallblks;
> @@ -1251,14 +1268,26 @@ retry_it:
>  		if (usb_write_10(srb, ss, start, smallblks)) {
>  			debug("Write ERROR\n");
>  			usb_request_sense(srb, ss);
> -			if (retry--)
> +			if (retry--) {
> +				/* decrease the USB_MAX_XFER_BLK */
> +				if (next >  0) {
> +					smallblks = usb_xfer_blk_tbl[--next];
> +					USB_MAX_XFER_BLK = smallblks;
> +				}
> +				retry_flag = true;
>  				goto retry_it;
> +			}
>  			blkcnt -= blks;
>  			break;
>  		}
>  		start += smallblks;
>  		blks -= smallblks;
>  		buf_addr += srb->datalen;
> +
> +		/* try to increase the USB_MAX_XFER_BLK */
> +		if (next < USB_XFER_BLK_TBL_SZ  - 1)
> +			if (!retry_flag && usb_xfer_blk_tbl[next + 1] <= blks)
> +				USB_MAX_XFER_BLK = usb_xfer_blk_tbl[++next];
>  	} while (blks != 0);
>  	ss->flags &= ~USB_READY;
>  
> @@ -1331,6 +1360,9 @@ int usb_storage_probe(struct usb_device *dev, unsigned int ifnum,
>  		break;
>  	}
>  
> +	/* Initialize the current transfer blocks to minimum value */
> +	USB_MAX_XFER_BLK = usb_xfer_blk_tbl[0];
> +
>  	/*
>  	 * We are expecting a minimum of 2 endpoints - in and out (bulk).
>  	 * An optional interrupt is OK (necessary for CBI protocol).
> 


-- 
Best regards,
Marek Vasut