[U-Boot] [PATCH v5 2/2] common: usb_storage : Implement logic to calculate optimal usb maximum trasfer blocks

[Marek Vasut <marex@denx.de>]

On 06/14/2016 05:41 AM, Rajesh Bhagat wrote:
> 
> 
>> -----Original Message-----
>> From: Marek Vasut [mailto:marex at denx.de]
>> Sent: Monday, June 13, 2016 7:07 PM
>> To: Rajesh Bhagat <rajesh.bhagat@nxp.com>; u-boot at lists.denx.de
>> Cc: sjg at chromium.org; york sun <york.sun@nxp.com>; Sriram Dash
>> <sriram.dash@nxp.com>; Rajesh Bhagat <rajesh.bhagat@freescale.com>
>> Subject: Re: [PATCH v5 2/2] common: usb_storage : Implement logic to calculate
>> optimal usb maximum trasfer blocks
>>
>> On 06/13/2016 06:03 AM, Rajesh Bhagat wrote:
>>> From: Rajesh Bhagat <rajesh.bhagat@freescale.com>
>>>
>>> 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@nxp.com>
>>> Signed-off-by: Rajesh Bhagat <rajesh.bhagat@nxp.com>
>>> ---
>>> Changes in v5:
>>>  - None
>>>
>>> Changes in v4:
>>>  - Adds udev paramater in dec/inc_cur_xfer_blks function and adds
>>>    sanity check on it.
>>>  - Changes type of pos varible to unsigned int in
>>> dec/inc_cur_xfer_blks
>>>  - Removes usage of pos varible from usb_stor_read/write
>>>
>>> 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 |   67
>> ++++++++++++++++++++++++++++++++++++++++++++++---
>>>  include/usb.h        |    1 +
>>>  2 files changed, 63 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/common/usb_storage.c b/common/usb_storage.c index
>>> f060637..9b09412 100644
>>> --- a/common/usb_storage.c
>>> +++ b/common/usb_storage.c
>>> @@ -106,11 +106,16 @@ 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 + 1) /
>> (USB_MIN_XFER_BLK + 1)))
>>> +#define CALC_CUR_XFER_BLKS(pos)	((1 << (12 + pos)) - 1)
> 
> Hello Marek,
> 
>>
>> Parenthesis around variables are missing.
>>
> 
> Will take care in v6. 
> 
>>>  #ifndef CONFIG_BLK
>>>  static struct us_data usb_stor[USB_MAX_STOR_DEV];  #endif @@ -141,6
>>> +146,44 @@ static void usb_show_progress(void)
>>>  	debug(".");
>>>  }
>>>
>>> +static int dec_cur_xfer_blks(struct usb_device *udev) {
>>> +	/* decrease the cur_xfer_blks */
>>> +	unsigned int pos;
>>> +	unsigned short size;
>>> +
>>> +	if (!udev)
>>> +		return -EINVAL;
>>> +
>>> +	pos = GET_CUR_XFER_BLKS(udev->cur_xfer_blks);
>>> +	size  = pos ? CALC_CUR_XFER_BLKS(pos - 1) : 0;
>>
>> If pos == 0 , the condition below will be true (size will be 2047), so this extra ternary
>> is unnecessary.
>>
> 
> Will take care in v6. Will remove the extra ternary operator used, as 2047 will follow the 
> below check (size < USB_MIN_XFER_BLK) and code will work fine. 
> 
>>> +	if (size < USB_MIN_XFER_BLK)
>>> +		return -EINVAL;
>>> +
>>> +	udev->cur_xfer_blks = size;
>>> +	return 0;
>>> +}
>>> +
>>> +static int inc_cur_xfer_blks(struct usb_device *udev, lbaint_t blks)
>>> +{
>>> +	/* try to increase the cur_xfer_blks */
>>> +	unsigned int pos;
>>> +	unsigned short size;
>>> +
>>> +	if (!udev)
>>> +		return -EINVAL;
>>> +
>>> +	pos = GET_CUR_XFER_BLKS(udev->cur_xfer_blks);
>>> +	size = CALC_CUR_XFER_BLKS(pos + 1);
>>> +
>>> +	if (size > blks || size > USB_MAX_XFER_BLK)
>>> +		return -EINVAL;
>>
>> Why don't you clamp the size to min(blks, USB_MAX_XFER_BLK) instead ?
>>
> 
> Do you mean below statement?
> 
> if (size > min(blks, USB_MAX_XFER_BLK))
> 	return -EINVAL;

Yes, if that makes sense.


-- 
Best regards,
Marek Vasut