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spi: zynqmp_gqspi: fix set_speed bug on multiple runs

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If zynqmp_qspi_set_speed() is called multiple times with the same speed,
then on the second call it will skip recalculating the baud_rate_val as
it assumes the speed is already configured correctly. But it will still
write the baud_rate_val to the configuration register and call
zynqmp_gqspi_set_tapdelay(). Because it skipped recalculating the
baud_rate_val, it will use the initial value of 0 . This causes the
driver to run at maximum speed which for many spi flashes is too fast and
causes data corruption.

Instead only write out a new baud_rate_val if we have calculated the
correct baud_rate_val.

This opens up another issue with the "if (speed == 0)", we don't save
off the new plat->speed_hz value when setting the baud rate on the
speed=0 path. Instead mimic what the Linux zynqmp gqspi driver does, and
have speed==0 just use the same calculation as a normal speed. That will
cause the baud_rate_val to use the slowest speed possible, which is the
safest option.

Signed-off-by: Brandon Maier <brandon.maier@rockwellcollins.com>
CC: jagan@amarulasolutions.com
CC: michal.simek@xilinx.com
CC: Ashok Reddy Soma <ashokred@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
This commit is contained in:
Brandon Maier 2021-01-20 14:28:30 -06:00 committed by Michal Simek
parent 3600d47b73
commit d9aa19efa8
1 changed files with 11 additions and 12 deletions
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23
drivers/spi/zynqmp_gqspi.c
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@ -320,12 +320,9 @@ static int zynqmp_qspi_set_speed(struct udevice *bus, uint speed)
if (speed > plat->frequency)
speed = plat->frequency;
/* Set the clock frequency */
confr = readl(&regs->confr);
if (speed == 0) {
/* Set baudrate x8, if the freq is 0 */
baud_rate_val = GQSPI_DFLT_BAUD_RATE_VAL;
} else if (plat->speed_hz != speed) {
if (plat->speed_hz != speed) {
/* Set the clock frequency */
/* If speed == 0, default to lowest speed */
while ((baud_rate_val < 8) &&
((plat->frequency /
(2 << baud_rate_val)) > speed))
@ -335,13 +332,15 @@ static int zynqmp_qspi_set_speed(struct udevice *bus, uint speed)
baud_rate_val = GQSPI_DFLT_BAUD_RATE_VAL;
plat->speed_hz = plat->frequency / (2 << baud_rate_val);
}
confr &= ~GQSPI_BAUD_DIV_MASK;
confr |= (baud_rate_val << 3);
writel(confr, &regs->confr);
zynqmp_qspi_set_tapdelay(bus, baud_rate_val);
debug("regs=%p, speed=%d\n", priv->regs, plat->speed_hz);
confr = readl(&regs->confr);
confr &= ~GQSPI_BAUD_DIV_MASK;
confr |= (baud_rate_val << 3);
writel(confr, &regs->confr);
zynqmp_qspi_set_tapdelay(bus, baud_rate_val);
debug("regs=%p, speed=%d\n", priv->regs, plat->speed_hz);
}
return 0;
}