Messages in this thread | | | Date | Thu, 24 Nov 2022 12:16:10 +0530 | Subject | Re: [PATCH] spi: cadence-quadspi: Add upper limit safety check to baudrate divisor | From | Dhruva Gole <> |
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Hi Nathan, Thanks for your contribution. However, there are a few issues that I would like you to address.
On 24/11/22 02:47, Nathan Barrett-Morrison wrote: > While bringing up the cadence-quadspi driver on a customer board, > I discovered that the baud divisor calculation can exceed the > peripheral's maximum in some circumstances. This will prevent it. What is the peripheral's maximum? Is the peripheral a flash? Please define what you mean by "some circumstances".
> > Signed-off-by: Nathan Barrett-Morrison <nathan.morrison@timesys.com> > --- > drivers/spi/spi-cadence-quadspi.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c > index 447230547945..250575fb7b0e 100644 > --- a/drivers/spi/spi-cadence-quadspi.c > +++ b/drivers/spi/spi-cadence-quadspi.c > @@ -1119,6 +1119,10 @@ static void cqspi_config_baudrate_div(struct cqspi_st *cqspi) > /* Recalculate the baudrate divisor based on QSPI specification. */ > div = DIV_ROUND_UP(ref_clk_hz, 2 * cqspi->sclk) - 1; > > + /* Maximum baud divisor */ > + if (div > CQSPI_REG_CONFIG_BAUD_MASK)
I don't think comparing "greater than" with a MASK is atall a good idea.
> + div = CQSPI_REG_CONFIG_BAUD_MASK; I would not encourage this either.
> + > reg = readl(reg_base + CQSPI_REG_CONFIG); > reg &= ~(CQSPI_REG_CONFIG_BAUD_MASK << CQSPI_REG_CONFIG_BAUD_LSB); > reg |= (div & CQSPI_REG_CONFIG_BAUD_MASK) << CQSPI_REG_CONFIG_BAUD_LSB;
Either come up with a better MACRO, or if what I understand is correct, the peripheral's max value will depend, well on the _peripheral_ in which case it is that "peripheral" driver's responsibility to properly tell the controller what to do.
Again, I don't fully understand your situation is as in what is the peripheral you are using. So please elaborate on that.
Importantly, I would suggest that you _NEVER_ compare ANY value to a MASK Macro. MASK Macros are meant to MASK bits.
-- Thanks and Regards, Dhruva Gole
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