[U-Boot] [PATCH v3 2/2] usb: Add CONFIG to fetch string descriptor

[puneets]

Hi Marek,
On Monday 05 March 2012 06:18 PM, Marek Vasut wrote:
> Dear Puneet Saxena,
>
>>> Hi Marek,
>>>
>>> On Thursday 01 March 2012 05:15 PM, Marek Vasut wrote:
>>>> Hi!
>>>>
>>>>> Hi Marek,
>>>>>
>>>>> On Thursday 01 March 2012 02:59 AM, Marek Vasut wrote:
>>>>>>> Add "CONFIG_USB_STRING_FETCH" to fetch first string descriptor
>>>>>>> length and then pass this length to fetch string descriptor.
>>>>>>>
>>>>>>> Signed-off-by: Puneet Saxena<puneets at nvidia.com>
>>>>>>> ---
>>>>>>>
>>>>>>> Changes for V2:
>>>>>>>       - Change existing config by "CONFIG_USB_STRING_FETCH"
>>>>>>>
>>>>>>> Changes for V3:
>>>>>>>        - Removed extra new line
>>>>>>>        - Explained "CONFIG_USB_STRING_FETCH" in top level README
>>>>>>>
>>>>>>>     README                          |    4 ++++
>>>>>>>     common/usb.c                    |    4 ++++
>>>>>>>     include/configs/tegra2-common.h |    2 ++
>>>>>>>     3 files changed, 10 insertions(+), 0 deletions(-)
>>>>>>>
>>>>>>> diff --git a/README b/README
>>>>>>> index 7adf7c7..c045a37 100644
>>>>>>> --- a/README
>>>>>>> +++ b/README
>>>>>>>
>>>>>>> @@ -1138,6 +1138,10 @@ The following options need to be configured:
>>>>>>>     		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
>>>>>>>     		txfilltuning field in the EHCI controller on reset.
>>>>>>>
>>>>>>> +		CONFIG_USB_STRING_FETCH
>>>>>>> +		Enables settings to USB core to handle string issues
>> which
>>
>>>>>>> +		few devices can not handle.
>>>>>>> +
>>>>>>>
>>>>>>>     - USB Device:
>>>>>>>     		Define the below if you wish to use the USB console.
>>>>>>>     		Once firmware is rebuilt from a serial console issue the
>>>>>>>
>>>>>>> diff --git a/common/usb.c b/common/usb.c
>>>>>>> index 191bc5b..a73cb60 100644
>>>>>>> --- a/common/usb.c
>>>>>>> +++ b/common/usb.c
>>>>>>> @@ -658,9 +658,13 @@ static int usb_string_sub(struct usb_device
>>>>>>> *dev, unsigned int langid, {
>>>>>>>
>>>>>>>     	int rc;
>>>>>>>
>>>>>>> +#ifdef CONFIG_USB_STRING_FETCH
>>>>>> Shouldn't this be something like ... CONFIG_USB_AVOID_STRING_FETCH
>>>>>> then?
>>>>>>
>>>>>> Anyway, how come some devices can't handle it? What happens then?
>>>>>> What devices are those (exact type etc)?
>>>>>>
>>>>>> I believe the bug is deeper and adding extra config options can be
>>>>>> avoided, what do you think?
>>>>>>
>>>>>> Thanks!
>>>>>>
>>>>>> M
>>>>> It does not avoid string fetch.
>>>> Well it does certainly not call usb_get_string()
>>> Precisely, it avoids fetching string desc of 255 bytes. so better name
>>> could be
>>> "CONFIG_USB_AVOID_STRING_FETCH_255".  Thanks for your comment.
>>>
>>>>> I checked with few mass storage devices that they does not handle
>>>>> string descriptor request correctly and so we get
>>>>> start/stop Cache alignment error.
>>>> Cache alignment error ? Wow, how's that actually related to SUB string
>>>> fetching? Maybe we should manually realign the result then? I still
>>>> don't really understand what you're seeing, sorry ... can you please
>>>> elaborate?
>>> The particular mass storage device is -
>>>
>>> Vendor: Kingston Rev: PMAP Prod: DataTraveler 2.0
>>>
>>> Type: Removable Hard Disk
>>>
>>> Capacity: 1906.0 MB = 1.8 GB (3903488 x 512)
>>>
>>> When code tries to read Manufacturing Id..prod id...etc..it passes cache
>>> aligned buffer "tbuf" in
>>> "usb_string()" @usb.c. Inside "usb_string_sub()", usb_get_string()
>>> passes as default 255 bytes to fetch string
>>> descriptor.
>>> The code in "ehci_submit_async() " invalidates *partially* the passed
>>> buffer though we pass aligned buffer and "STD_ASS"
>>> is received. Though it should invalidate only the cached line which is
>>> equal(~32)  to string desc length.
>> Hm ... so this means the bug is in ehci_hcd? Maybe the ehci_hcd should be
>> fixed to correctly handle caches then?
>>
>>> If we give delay of 1 ms after handshake() the cache alignment warning
>>> does not spew...but delay of 1 ms is not acceptable.
>>> So I enabled the code to fetch first string desc length and then fetch
>>> string desc fetch, in this way the issue is resolved.
>>> It makes sense also to fetch string desc length and then actual string
>>> desc....
>> I see, I  understand now just about everything but the ehci problem, see
>> above. Your explanation was very helpful.
>>
>> Let's work this out together!
>>
>> Cheers!
>>
>> M
> Is this issue fixed or is this patch still needed? Thanks in advance!
This issue is not fixed and still need a patch to fix root cause, 
explained above.
Note that this issue is observed even though we pass aligned address and
expects something from the device.
> Best regards,
> Marek Vasut
Thanx & Regards,
Puneet

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