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30735584a4
The GD32VW55x I2C master (the STM32-style "v2" IP) never completed a real
transfer. Two bugs:
1. Wrong kernel clock. The protocol state machine is clocked by the I2C
kernel clock selected in RCU_CFG1.I2C0SEL, not by the APB1 bus clock that
only feeds the register interface. The driver left it at the APB1 default
and computed TIMING for PCLK1 (~80 MHz); the resulting prescaled period is
so short that the SDADEL/SCLDEL setup and hold times fall below the
analog-filter minimum of the IP, so the master latches START but never
drives SCL (STAT stuck with BUSY set). Route I2C0 to IRC16M (16 MHz) and
use it as clk_freq, and never let the prescaler drop below the value that
keeps the prescaled clock at/under 4 MHz (250 ns) so SDADEL/SCLDEL stay in
spec. This matches the vendor BSP (IRC16M, PSC=3).
2. Transfer timeout was zero. CONFIG_GD32VW55X_I2C_TIMEOTICKS has a Kconfig
default of 0 ("override when non-zero"), but the driver derived the timeout
with a plain #ifndef, which never triggers because the symbol is always
defined. The polled wait loop therefore ran a single iteration and gave
up. Address probes (NACK on the first pass) still worked and masked it;
only multi-byte transfers exercised the loop. Honour the "0 means derive
from seconds/milliseconds" contract.
Also make the interrupt wait immune to the ISR completing between startmsg()
and the wait (do not clobber a posted DONE), and drop a redundant cast.
To exercise this on hardware, add an "sht3x" configuration to the
gd32vw553k-start: the nsh base plus I2C0, the i2ctool and the Sensirion SHT3x
temperature/humidity driver, registered as /dev/i2c0 and /dev/temp0. I2C0 is
routed to PA2 (SCL) / PA3 (SDA) on AF4, the pins broken out on the J1 header
(datasheet Table 2-5); when SPI is enabled it claims PA2, so I2C0 falls back
to PB0/PB1, whose SDA pin is not broken out (the periph case).
Signed-off-by: Jorge Guzman <jorge.gzm@gmail.com>
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