The current ds_read_block function only supports block sizes up to
128 bytes, which is the depth of the 'data out' fifo on the ds2490.
Reading larger blocks will fail with a: -110 (ETIMEDOUT) from
usb_control_msg(). Example:
$ dd if=/sys/bus/w1/devices/43-000000478756/eeprom bs=256 count=1
yields to the following message from the kernel:
usb 5-1: Failed to write 1-wire data to ep0x2: err=-110.
I discovered this issue while implementing support for the ds28ec20
eeprom in the w1-2433 driver. This driver accepts reading blocks of
sizes up to the size of the entire memory (2560 bytes in the case of
the ds28ec20). Note that this issue _does not_ arise when the kernel
is configured with CONFIG_W1_SLAVE_DS2433_CRC enabled since in this
mode the driver reads one 32 byte block at a time (a single memory
page).
Also, from the ds2490 datasheet (2995.pdf, page 22, BLOCK I/O
command):
For a block write sequence the EP2 FIFO must be pre-filled with
data before command execution. Additionally, for block sizes
greater then the FIFO size, the FIFO content status must be
monitored by host SW so that additional data can be sent to the
FIFO when necessary. A similar EP3 FIFO content monitoring
requirement exists for block read sequences. During a block read
the number of bytes loaded into the EP3 FIFO must be monitored so
that the data can be read before the FIFO overflows.
Breaking the block in smaller 128 bytes chunks and simply calling the
original code sequence has solved the issue for me.
Tested with a DS1490F usb<->one-wire adapter and both the DS28EC20 and
DS2433 eeprom memories.
Signed-off-by: Marc Ferland <marc.ferland@sonatest.com>
Link: https://lore.kernel.org/r/20231218150230.1992448-2-marc.ferland@sonatest.com
[krzysztof: fix checkpatch 'spaces preferred around']
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
d605ba72e9