[U-Boot] [PATCH v3] common: usb_storage : Implement logic to calculate optimal usb maximum trasfer blocks

[Marek Vasut]

On 06/08/2016 06:09 AM, Rajesh Bhagat wrote:
> 
> 
>> -----Original Message-----
>> From: Marek Vasut [mailto:marex at denx.de]
>> Sent: Wednesday, June 08, 2016 8:38 AM
>> To: Rajesh Bhagat <rajesh.bhagat at nxp.com>; u-boot at lists.denx.de
>> Cc: sjg at chromium.org; york sun <york.sun at nxp.com>; Sriram Dash
>> <sriram.dash at nxp.com>
>> Subject: Re: [PATCH v3] common: usb_storage : Implement logic to calculate optimal
>> usb maximum trasfer blocks
>>
>> On 06/07/2016 11:29 AM, 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 defines USB_MIN_XFER_BLK/USB_MAX_XFER_BLK 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 and max = 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>
>>> ---
>>> Changes in v3:
>>>  - Adds cur_xfer_blks in struct usb_device to retain values
>>>  - Adds functions dec/inc_cur_xfer_blks to remove code duplication
>>>  - Moves check from macro to calling functions
>>>
>>> Changes in v2:
>>>  - Removes table to store blocks and use formula (1 << (12 + n)) - 1
>>>  - Adds logic to start from minimum, go to maximum in each read/write
>>>
>>>  common/usb_storage.c | 78
>> ++++++++++++++++++++++++++++++++++++++++++++--------
>>>  include/usb.h        |  1 +
>>>  2 files changed, 67 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/common/usb_storage.c b/common/usb_storage.c index
>>> 7e6e52d..e08dcd4 100644
>>> --- a/common/usb_storage.c
>>> +++ b/common/usb_storage.c
>>> @@ -106,11 +106,40 @@ struct us_data {
>>>   * enough free heap space left, but the SCSI READ(10) and WRITE(10) commands
>> are
>>>   * limited to 65535 blocks.
>>>   */
>>> +#define USB_MIN_XFER_BLK	4095
>>>  #define USB_MAX_XFER_BLK	65535
>>>  #else
>>> +#define USB_MIN_XFER_BLK	20
>>>  #define USB_MAX_XFER_BLK	20
>>>  #endif
>>>
>>> +#define GET_CUR_XFER_BLKS(blks)	(LOG2(blks / (USB_MIN_XFER_BLK +
>> 1)))
>>> +#define CALC_CUR_XFER_BLKS(pos)	((1 << (12 + pos)) - 1)
>>> +
>>> +static int dec_cur_xfer_blks(int *pos, unsigned short *smallblks) {
>>> +	/* decrease the cur_xfer_blks */
>>> +	unsigned short size = (*pos > 0) ? CALC_CUR_XFER_BLKS(*pos - 1) : 0;
>>
> 
> Hello Marek, 
> 
>> If someone passes null pointer into the function, it will fail.
>> Also, you can refactor it to make it more readable:
>>
>> if (!pos)
>>  return -EINVAL;
>> if (size < USB_MIN_XFER_BLK)
>>  return -EINVAL;
>> ... do stuff ...
>>
> 
> Refactoring the code to return early in case of error conditions is fine. But 
> pos and smallblks can never be passed as NULL in these functions. 

... until an idiot comes around and does it.

>> I still don't understand why $pos isn't unsigned int, it should be.
>>
> 
> I believe keeping a variable as "int" provides a natural way of checking for 
> overflow conditions. We check can check if number has become negative and take 
> actions, which is not possible when number is taken as "unsigned int".

But the number here can never be negative, can it ?

>>> +	if (size >= USB_MIN_XFER_BLK) {
>>> +		*smallblks = size;
>>> +		(*pos)--;
>>> +		return 0;
>>> +	}
>>> +	return -EINVAL;
>>> +}
>>> +
>>> +static int inc_cur_xfer_blks(int *pos, unsigned short *smallblks,
>>> +lbaint_t blks) {
>>> +	/* try to increase the cur_xfer_blks */
>>> +	unsigned short size = (*pos >= 0) ? CALC_CUR_XFER_BLKS(*pos + 1) : 0;
>>> +	if (size <= blks && size <= USB_MAX_XFER_BLK) {
>>> +		*smallblks = size;
>>> +		(*pos)++;
>>> +		return 0;
>>> +	}
>>> +	return -EINVAL;
>>> +}
>>> +
>>>  #ifndef CONFIG_BLK
>>>  static struct us_data usb_stor[USB_MAX_STOR_DEV];  #endif @@ -1117,7
>>> +1146,8 @@ 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, pos;
>>> +	bool retry_flag = false;
>>>  	ccb *srb = &usb_ccb;
>>>  #ifdef CONFIG_BLK
>>>  	struct blk_desc *block_dev;
>>> @@ -1145,6 +1175,7 @@ static unsigned long usb_stor_read(struct blk_desc
>> *block_dev, lbaint_t blknr,
>>>  	buf_addr = (uintptr_t)buffer;
>>>  	start = blknr;
>>>  	blks = blkcnt;
>>> +	pos = GET_CUR_XFER_BLKS(udev->cur_xfer_blks);
>>
>> Is this $pos even needed ? Why ?
> 
> $pos variable is updated in dec/inc_cur_xfer_blks functions which calculates the 
> next transfer blocks, and finally when all conditions are met is stored in udev->cur_xfer_blks.

And why doesn't this work with udev->cur_xfer_blks directly ?

>>
>>>  	debug("\nusb_read: dev %d startblk " LBAF ", blccnt " LBAF " buffer %"
>>>  	      PRIxPTR "\n", block_dev->devnum, start, blks, buf_addr); @@
>>> -1153,26 +1184,35 @@ static unsigned long usb_stor_read(struct blk_desc
>> *block_dev, lbaint_t blknr,
>>>  		/* XXX need some comment here */
>>>  		retry = 2;
>>>  		srb->pdata = (unsigned char *)buf_addr;
>>> -		if (blks > USB_MAX_XFER_BLK)
>>> -			smallblks = USB_MAX_XFER_BLK;
>>> +		if (blks > udev->cur_xfer_blks)
>>> +			smallblks = udev->cur_xfer_blks;
>>>  		else
>>>  			smallblks = (unsigned short) blks;
>>>  retry_it:
>>> -		if (smallblks == USB_MAX_XFER_BLK)
>>> +		debug("usb_read: retry #%d, cur_xfer_blks %hu, smallblks %hu\n",
>>> +		      retry, udev->cur_xfer_blks, smallblks);
>>> +		if (smallblks == udev->cur_xfer_blks)
>>>  			usb_show_progress();
>>>  		srb->datalen = block_dev->blksz * smallblks;
>>>  		srb->pdata = (unsigned char *)buf_addr;
>>>  		if (usb_read_10(srb, ss, start, smallblks)) {
>>>  			debug("Read ERROR\n");
>>>  			usb_request_sense(srb, ss);
>>> -			if (retry--)
>>> +			if (retry--) {
>>> +				if (!dec_cur_xfer_blks(&pos, &smallblks))
>>> +					udev->cur_xfer_blks = smallblks;
>>> +				retry_flag = true;
>>>  				goto retry_it;
>>> +			}
>>>  			blkcnt -= blks;
>>
>> The same piece of code is below. I would rather see you factor out the common code
>> and then make any changes.
>>
> 
> IMHO, All the common code is moved in functions dec/inc_cur_xfer_blks as pointed earlier.
> Are you are referring to other common code of usb_stor_read/write functions which is not
> part of this patchset. If yes, I would prefer to take it as a next patch set. 

Please don't add new stuff to code which needs fixing first, that's not
a good practice. Prepare the ground first and then add new stuff.

> Best Regards,
> Rajesh Bhagat 
> 
>>>  			break;
>>>  		}
>>>  		start += smallblks;
>>>  		blks -= smallblks;
>>>  		buf_addr += srb->datalen;
>>> +
>>> +		if (!retry_flag && !inc_cur_xfer_blks(&pos, &smallblks, blks))
>>> +			udev->cur_xfer_blks = smallblks;
>>>  	} while (blks != 0);
>>>  	ss->flags &= ~USB_READY;
>>>
>>> @@ -1181,7 +1221,7 @@ retry_it:
>>>  	      start, smallblks, buf_addr);
>>>
>>>  	usb_disable_asynch(0); /* asynch transfer allowed */
>>> -	if (blkcnt >= USB_MAX_XFER_BLK)
>>> +	if (blkcnt >= udev->cur_xfer_blks)
>>>  		debug("\n");
>>>  	return blkcnt;
>>>  }
>>> @@ -1199,7 +1239,8 @@ 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, pos;
>>> +	bool retry_flag = false;
>>>  	ccb *srb = &usb_ccb;
>>>  #ifdef CONFIG_BLK
>>>  	struct blk_desc *block_dev;
>>> @@ -1222,6 +1263,7 @@ static unsigned long usb_stor_write(struct blk_desc
>> *block_dev, lbaint_t blknr,
>>>  	}
>>>  #endif
>>>  	ss = (struct us_data *)udev->privptr;
>>> +	pos = GET_CUR_XFER_BLKS(udev->cur_xfer_blks);
>>>
>>>  	usb_disable_asynch(1); /* asynch transfer not allowed */
>>>
>>> @@ -1239,26 +1281,35 @@ static unsigned long usb_stor_write(struct blk_desc
>> *block_dev, lbaint_t blknr,
>>>  		 */
>>>  		retry = 2;
>>>  		srb->pdata = (unsigned char *)buf_addr;
>>> -		if (blks > USB_MAX_XFER_BLK)
>>> -			smallblks = USB_MAX_XFER_BLK;
>>> +		if (blks > udev->cur_xfer_blks)
>>> +			smallblks = udev->cur_xfer_blks;
>>>  		else
>>>  			smallblks = (unsigned short) blks;
>>>  retry_it:
>>> -		if (smallblks == USB_MAX_XFER_BLK)
>>> +		debug("usb_write: retry #%d, cur_xfer_blks %hu, smallblks %hu\n",
>>> +		      retry, udev->cur_xfer_blks, smallblks);
>>> +		if (smallblks == udev->cur_xfer_blks)
>>>  			usb_show_progress();
>>>  		srb->datalen = block_dev->blksz * smallblks;
>>>  		srb->pdata = (unsigned char *)buf_addr;
>>>  		if (usb_write_10(srb, ss, start, smallblks)) {
>>>  			debug("Write ERROR\n");
>>>  			usb_request_sense(srb, ss);
>>> -			if (retry--)
>>> +			if (retry--) {
>>> +				if (!dec_cur_xfer_blks(&pos, &smallblks))
>>> +					udev->cur_xfer_blks = smallblks;
>>> +				retry_flag = true;
>>>  				goto retry_it;
>>> +			}
>>>  			blkcnt -= blks;
>>>  			break;
>>>  		}
>>>  		start += smallblks;
>>>  		blks -= smallblks;
>>>  		buf_addr += srb->datalen;
>>> +
>>> +		if (!retry_flag && !inc_cur_xfer_blks(&pos, &smallblks, blks))
>>> +			udev->cur_xfer_blks = smallblks;
>>>  	} while (blks != 0);
>>>  	ss->flags &= ~USB_READY;
>>>
>>> @@ -1266,7 +1317,7 @@ retry_it:
>>>  	      PRIxPTR "\n", start, smallblks, buf_addr);
>>>
>>>  	usb_disable_asynch(0); /* asynch transfer allowed */
>>> -	if (blkcnt >= USB_MAX_XFER_BLK)
>>> +	if (blkcnt >= udev->cur_xfer_blks)
>>>  		debug("\n");
>>>  	return blkcnt;
>>>
>>> @@ -1331,6 +1382,9 @@ int usb_storage_probe(struct usb_device *dev, unsigned
>> int ifnum,
>>>  		break;
>>>  	}
>>>
>>> +	/* Initialize the current transfer blocks to minimum value */
>>> +	dev->cur_xfer_blks = USB_MIN_XFER_BLK;
>>> +
>>>  	/*
>>>  	 * We are expecting a minimum of 2 endpoints - in and out (bulk).
>>>  	 * An optional interrupt is OK (necessary for CBI protocol).
>>> diff --git a/include/usb.h b/include/usb.h index 02a0ccd..bd49014
>>> 100644
>>> --- a/include/usb.h
>>> +++ b/include/usb.h
>>> @@ -153,6 +153,7 @@ struct usb_device {
>>>  	struct udevice *dev;		/* Pointer to associated device */
>>>  	struct udevice *controller_dev;	/* Pointer to associated controller */
>>>  #endif
>>> +	unsigned short cur_xfer_blks;	/* Current maximum transfer blocks */
>>>  };
>>>
>>>  struct int_queue;
>>>
>>
>>
>> --
>> Best regards,
>> Marek Vasut


-- 
Best regards,
Marek Vasut