Hi Paul,
Thanks for your comments.
>Subject: Re: [PATCH v1 3/3] Bluetooth: btintel_pcie: Reduce driver buffer
>posting to prevent race condition
>
>Dear Chandrashekar, dear Kiran,
>
>
>Thank you for the patch.
>
>Am 25.05.25 um 07:39 schrieb Kiran K:
>> From: Chandrashekar Devegowda <chandrashekar.devegowda@xxxxxxxxx>
>>
>> Modify the driver to post 3 fewer buffers than the maximum rx buffers
>> (64) allowed for the firmware. This change mitigates a hardware issue
>> causing a race condition in the firmware, improving stability and data
>> handling.
>
>Interesting. Please elaborate, which firmware versions are affected, and if a fix
>is going to be expected, and how to reproduce the issue, so it can be tested
>without and with your patch.
>
The firmware is for the upcoming product and is not available in public yet. As I said in 1/3, the issue is seen on android kernel and it's very hard to reproduce the issue on vanilla kernel.
>Is the errata published?
>
Our internal documents are updated. I have also entered a comment in code.
> Why three buffers less and not two or four?
The recommendation from firmware / HW is to use at least 3 buffers as guard buffers. Anything less than three causes RFH (receive flow handler - RX path) blockage.
>Out of curiosity: Does the Microsoft Windows driver do the same?
Yes.
>
>> Signed-off-by: Chandrashekar Devegowda
>> <chandrashekar.devegowda@xxxxxxxxx>
>> Signed-off-by: Kiran K <kiran.k@xxxxxxxxx>
>> ---
>> drivers/bluetooth/btintel_pcie.c | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/bluetooth/btintel_pcie.c
>> b/drivers/bluetooth/btintel_pcie.c
>> index 03f13de4a723..14f000e08e1e 100644
>> --- a/drivers/bluetooth/btintel_pcie.c
>> +++ b/drivers/bluetooth/btintel_pcie.c
>> @@ -398,7 +398,10 @@ static int btintel_pcie_start_rx(struct
>btintel_pcie_data *data)
>> int i, ret;
>> struct rxq *rxq = &data->rxq;
>>
>> - for (i = 0; i < rxq->count; i++) {
>> + /* Post (BTINTEL_PCIE_RX_DESCS_COUNT - 3) buffers to overcome the
>> + * hardware issues leading to race condition at the firmware.
>
>If you had an errata, it’d be great to document it here to.
>
>I’d remove *the*.
Ack
>
>> + */
>> + for (i = 0; i < rxq->count - 3; i++) {
>> ret = btintel_pcie_submit_rx(data);
>> if (ret)
>> return ret;
>
>
>Kind regards,
>
>Paul
Regards,
Kiran
