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SubjectRe: [PATCHv2] mtd: spi-nor: cadence-quadspi: add reset control
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Hi, Dinh,

On 04/09/2019 06:38 PM, Dinh Nguyen wrote:
> Get the reset control for the QSPI controller and bring it out of reset.

Is there a public datasheet where I can check this?
>
> Suggested-by: Tien-Fong Chee <tien.fong.chee@intel.com>
> Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
> ---
> v2: use devm_reset_control_get_optional_exclusive
> print an error message
> return -EPROBE_DEFER
> ---
> drivers/mtd/spi-nor/cadence-quadspi.c | 14 ++++++++++++++

would you update the bindings as well?

> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
> index 792628750eec..c548567adcf0 100644
> --- a/drivers/mtd/spi-nor/cadence-quadspi.c
> +++ b/drivers/mtd/spi-nor/cadence-quadspi.c
> @@ -34,6 +34,7 @@
> #include <linux/of.h>
> #include <linux/platform_device.h>
> #include <linux/pm_runtime.h>
> +#include <linux/reset.h>
> #include <linux/sched.h>
> #include <linux/spi/spi.h>
> #include <linux/timer.h>
> @@ -1336,6 +1337,7 @@ static int cqspi_probe(struct platform_device *pdev)
> struct cqspi_st *cqspi;
> struct resource *res;
> struct resource *res_ahb;
> + struct reset_control *rstc;
> const struct cqspi_driver_platdata *ddata;
> int ret;
> int irq;
> @@ -1362,6 +1364,18 @@ static int cqspi_probe(struct platform_device *pdev)
> return PTR_ERR(cqspi->clk);
> }
>
> + /* Obtain QSPI reset control */

OSPI version of the IP has been added recently. Is this available just for QSPI?

> + rstc = devm_reset_control_get_optional_exclusive(dev, NULL);
> + if (IS_ERR(rstc)) {
> + dev_err(dev, "Cannot get QSPI reset.\n");
> + if (PTR_ERR(rstc) == -EPROBE_DEFER)
> + return -EPROBE_DEFER;

why ignoring all the other possible errors? Maybe return PTR_ERR(rstc); ?

> + } else {
> + reset_control_assert(rstc);

Shouldn't the clock be enabled before asserting reset?

Does it matter if reset_control_assert() is returning any error?

> + udelay(1);

Is there a range or 1 us is the maximum time that we should wait?

> + reset_control_deassert(rstc);

Should we check if reset_control_deassert() is returning any error?

Cheers,
ta

> + }
> +
> /* Obtain and remap controller address. */
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> cqspi->iobase = devm_ioremap_resource(dev, res);
>
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