On 2018-02-28 04:45, Andy Gross wrote:
On Sat, Feb 03, 2018 at 01:28:14PM +0530, Abhishek Sahu wrote:
The BAM mode requires buffer for start tag data and tx, rx SG
list. Currently, this is being taken for maximum transfer length
(65K). But an I2C transfer can have multiple messages and each
message can be of this maximum length so the buffer overflow will
happen in this case. Since increasing buffer length won’t be
feasible since an I2C transfer can contain any number of messages
so this patch does following changes to make i2c transfers working
for multiple messages case.
1. Calculate the required buffers for 2 maximum length messages
(65K * 2).
2. Split the descriptor formation and descriptor scheduling.
The idea is to fit as many messages in one DMA transfers for 65K
threshold value (max_xfer_sg_len). Whenever the sg_cnt is
crossing this, then schedule the BAM transfer and subsequent
transfer will again start from zero.
Signed-off-by: Abhishek Sahu <absahu@xxxxxxxxxxxxxx>
I'm ok with this patch. I find the idea of a > 64k size message to be
something
that usually wouldn't be encountered, but... with some eeproms and
maybe TPMs
perhaps this could happen?
Reviewed-by: Andy Gross <andy.gross@xxxxxxxxxx>
Thanks Andy for reviewing this patch.
There are EEPROM available with 1MB size like AT24CM01 in which we can
read
complete flash (128 KB) in single go by one transfer with 2 read
messages of
64KB.
Thanks,
Abhishek
