[v3] ath10k: improve BDF search fallback strategy

Board data files wrapped inside board-2.bin files are
identified based on a combination of bus architecture,
chip-id, board-id or variants. Here is one such example
of a BDF entry in board-2.bin file:
bus=snoc,qmi-board-id=67,qmi-chip-id=320,variant=GO_XXXX
It is possible for few platforms none of the combinations
of bus,qmi-board,chip-id or variants match, e.g. if
board-id is not programmed and thus reads board-id=0xff,
there won't be any matching BDF to be found. In such
situations, the wlan will fail to enumerate.

Currently, to search for BDF, there are two fallback
boardnames creates to search for BDFs in case the full BDF
is not found. It is still possible that even the fallback
boardnames do not match.

As an improvement, search for BDF with full BDF combination
and perform the fallback searches by stripping down the last
elements until a BDF entry is found or none is found for all
possible BDF combinations.e.g.
Search for initial BDF first then followed by reduced BDF
names as follows:
bus=snoc,qmi-board-id=67,qmi-chip-id=320,variant=GO_XXXX
bus=snoc,qmi-board-id=67,qmi-chip-id=320
bus=snoc,qmi-board-id=67
bus=snoc
<No BDF found>

Tested-on: WCN3990/hw1.0 WLAN.HL.3.2.2.c10-00754-QCAHLSWMTPL-1
Signed-off-by: Abhishek Kumar <kuabhs@chromium.org>
---

Changes in v3:
- As discussed, instead of adding support for default BDF in DT, added
a method to drop the last elements from full BDF until a BDF is found.
- Previous patch was "ath10k: search for default BDF name provided in DT"

 drivers/net/wireless/ath/ath10k/core.c | 65 +++++++++++++-------------
 1 file changed, 32 insertions(+), 33 deletions(-)

Kalle Valo <kvalo@kernel.org> writes:

>>  static int ath10k_core_fetch_board_data_api_n(struct ath10k *ar,
>>  					      const char *boardname,
>> -					      const char *fallback_boardname1,
>> -					      const char *fallback_boardname2,
>>  					      const char *filename)
>>  {
>> -	size_t len, magic_len;
>> +	size_t len, magic_len, board_len;
>>  	const u8 *data;
>>  	int ret;
>> +	char temp_boardname[100];
>> +
>> +	board_len = 100 * sizeof(temp_boardname[0]);
>
> Why not:
>
> board_len = sizeof(temp_board-name);
>
> That way number 100 is used only once.

BTW I'm not sure if it makes sense to CC David, Eric, Jakub and Paolo.
I'm sure they get a lot of email already. And I would also drop netdev.

Abhishek Kumar <kuabhs@chromium.org> writes:

> Board data files wrapped inside board-2.bin files are
> identified based on a combination of bus architecture,
> chip-id, board-id or variants. Here is one such example
> of a BDF entry in board-2.bin file:
> bus=snoc,qmi-board-id=67,qmi-chip-id=320,variant=GO_XXXX
> It is possible for few platforms none of the combinations
> of bus,qmi-board,chip-id or variants match, e.g. if
> board-id is not programmed and thus reads board-id=0xff,
> there won't be any matching BDF to be found. In such
> situations, the wlan will fail to enumerate.
>
> Currently, to search for BDF, there are two fallback
> boardnames creates to search for BDFs in case the full BDF
> is not found. It is still possible that even the fallback
> boardnames do not match.
>
> As an improvement, search for BDF with full BDF combination
> and perform the fallback searches by stripping down the last
> elements until a BDF entry is found or none is found for all
> possible BDF combinations.e.g.
> Search for initial BDF first then followed by reduced BDF
> names as follows:
> bus=snoc,qmi-board-id=67,qmi-chip-id=320,variant=GO_XXXX
> bus=snoc,qmi-board-id=67,qmi-chip-id=320
> bus=snoc,qmi-board-id=67
> bus=snoc
> <No BDF found>
>
> Tested-on: WCN3990/hw1.0 WLAN.HL.3.2.2.c10-00754-QCAHLSWMTPL-1
> Signed-off-by: Abhishek Kumar <kuabhs@chromium.org>
> ---
>
> Changes in v3:
> - As discussed, instead of adding support for default BDF in DT, added
> a method to drop the last elements from full BDF until a BDF is found.
> - Previous patch was "ath10k: search for default BDF name provided in DT"
>
>  drivers/net/wireless/ath/ath10k/core.c | 65 +++++++++++++-------------
>  1 file changed, 32 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath10k/core.c b/drivers/net/wireless/ath/ath10k/core.c
> index 688177453b07..ebb0d2a02c28 100644
> --- a/drivers/net/wireless/ath/ath10k/core.c
> +++ b/drivers/net/wireless/ath/ath10k/core.c
> @@ -1426,15 +1426,31 @@ static int ath10k_core_search_bd(struct ath10k *ar,
>  	return ret;
>  }
>  
> +static bool ath10k_create_reduced_boardname(struct ath10k *ar, char *boardname)


"static int" as you use error values. Strange that the compiler doesn't
warn about that.

> +{
> +	/* Find last BDF element */
> +	char *last_field = strrchr(boardname, ',');
> +
> +	if (last_field) {
> +		/* Drop the last BDF element */
> +		last_field[0] = '\0';
> +		ath10k_dbg(ar, ATH10K_DBG_BOOT,
> +			   "boardname =%s\n", boardname);
> +		return 0;
> +	}
> +	return -ENODATA;

I would invert the check:

	if (!last_field)
        	return -ENODATA;

	/* Drop the last BDF element */
	last_field[0] = '\0';
	ath10k_dbg(ar, ATH10K_DBG_BOOT, "boot reduced boardname %s\n",
		   boardname);

	return 0;

Also I changed the style used in the debug message.

https://wireless.wiki.kernel.org/en/users/drivers/ath10k/codingstyle#debug_messages

>  	data += magic_len;
>  	len -= magic_len;
>  
> -	/* attempt to find boardname in the IE list */
> -	ret = ath10k_core_search_bd(ar, boardname, data, len);
> +	memcpy(temp_boardname, boardname, board_len);
> +	ath10k_dbg(ar, ATH10K_DBG_BOOT, "boardname :%s\n", boardname);

"boot boardname %s\n"

>  
> -	/* if we didn't find it and have a fallback name, try that */
> -	if (ret == -ENOENT && fallback_boardname1)
> -		ret = ath10k_core_search_bd(ar, fallback_boardname1, data, len);
> +retry_search:
> +	/* attempt to find boardname in the IE list */
> +	ret = ath10k_core_search_bd(ar, temp_boardname, data, len);
>  
> -	if (ret == -ENOENT && fallback_boardname2)
> -		ret = ath10k_core_search_bd(ar, fallback_boardname2, data, len);
> +	/* If the full BDF entry was not found then drop the last element and
> +	 * recheck until a BDF is found or until all options are exhausted.
> +	 */
> +	if (ret == -ENOENT)
> +		if (!ath10k_create_reduced_boardname(ar, temp_boardname))
> +			goto retry_search;
>  
>  	if (ret == -ENOENT) {
>  		ath10k_err(ar,
>  			   "failed to fetch board data for %s from %s/%s\n",
> -			   boardname, ar->hw_params.fw.dir, filename);
> +			   temp_boardname, ar->hw_params.fw.dir, filename);
>  		ret = -ENODATA;
>  	}

This is hard to read, what about the loop below? Though I'm sure I
missed some corner case but I hope you get the idea. It's always good to
have a limit for the loops to avoid looping forever.

	for (i = 0; i < 20; i++) {
		/* attempt to find boardname in the IE list */
		ret = ath10k_core_search_bd(ar, temp_boardname, data, len);
		if (ret != -ENOENT)
			/* found it or something was wrong */
			break;

		/* If the full BDF entry was not found then drop the last element and
		 * recheck until a BDF is found or until all options are exhausted.
		 */
		ret = ath10k_create_reduced_boardname(ar, temp_boardname);
		if (ret) {
			ath10k_err(ar,
				   "failed to fetch board data for %s from %s/%s\n",
				   temp_boardname, ar->hw_params.fw.dir, filename);
			ret = -ENODATA;
			break;
		}
	};

	if (ret)
		goto err;

        return 0;