Re: [PATCH] spi: zynqmp_gqspi: fix set_speed bug on multiple runs

[Michal Simek]

Hi Ashok

On 1/20/21 9:28 PM, Brandon Maier wrote:
> 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.ma...@rockwellcollins.com>
> CC: ja...@amarulasolutions.com
> CC: michal.si...@xilinx.com
> CC: Ashok Reddy Soma <ashok...@xilinx.com>
> ---
>  drivers/spi/zynqmp_gqspi.c | 23 +++++++++++------------
>  1 file changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/spi/zynqmp_gqspi.c b/drivers/spi/zynqmp_gqspi.c
> index c7db43a09a..6641c2e9d5 100644
> --- a/drivers/spi/zynqmp_gqspi.c
> +++ b/drivers/spi/zynqmp_gqspi.c
> @@ -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;
>  }
> 

Ashok: Can you please review this patch?

Thanks,
Michal