Re: [PATCHv5 2/2] mtd: spi-nor: cadence-quadspi: add reset control

[<Tudor.Ambarus@microchip.com>]

On 06/12/2019 05:37 PM, Dinh Nguyen wrote:
> External E-Mail
> 
> 
> Get the reset control properties for the QSPI controller and bring them
> out of reset. Most will have just one reset bit, but there is an additional
> OCP reset bit that is used ECC. The OCP reset bit will also need to get
> de-asserted as well. [1]
> 
> The reason this patch is needed is in the case where a bootloader leaves
> the QSPI controller in a reset state, or a state where init cannot occur
> successfully, this patch will put the QSPI controller into a clean state.
> 
> [1] https://www.intel.com/content/www/us/en/programmable/hps/arria-10/hps.html#reg_soc_top/sfo1429890575955.html
> 
> Suggested-by: Tien-Fong Chee <tien.fong.chee@intel.com>
> Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
> ---
> v5: remove udelay(not needed) on tested hardware
>     group reset assert/deassert together
>     update commit message with reasoning for patch
> v4: fix compile error
> v3: return full error by using PTR_ERR(rtsc)
>     move reset control calls until after the clock enables
>     use udelay(2) to be safe
>     Add optional OCP(Open Core Protocol) reset signal
> v2: use devm_reset_control_get_optional_exclusive
>     print an error message
>     return -EPROBE_DEFER
> ---
>  drivers/mtd/spi-nor/cadence-quadspi.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
> index 792628750eec..f8b1009e488c 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 +1337,8 @@ static int cqspi_probe(struct platform_device *pdev)
>  	struct cqspi_st *cqspi;
>  	struct resource *res;
>  	struct resource *res_ahb;
> +	struct reset_control *rstc;
> +	struct reset_control *rstc_ocp;
>  	const struct cqspi_driver_platdata *ddata;
>  	int ret;
>  	int irq;
> @@ -1402,6 +1405,29 @@ static int cqspi_probe(struct platform_device *pdev)
>  		goto probe_clk_failed;
>  	}
>  
> +	/* Obtain QSPI reset control */
> +	rstc = devm_reset_control_get_optional_exclusive(dev, "qspi");
> +	if (IS_ERR(rstc)) {
> +		dev_err(dev, "Cannot get QSPI reset.\n");
> +		return PTR_ERR(rstc);
> +	}
> +
> +	rstc_ocp = devm_reset_control_get_optional_exclusive(dev, "qspi-ocp");
> +	if (IS_ERR(rstc_ocp)) {
> +		dev_err(dev, "Cannot get QSPI OCP reset.\n");
> +		return PTR_ERR(rstc_ocp);
> +	}
> +
> +	if (rstc) {

Hi, Dinh,

reset_control_assert/deassert() already have checks for null, you can call them
directly without checking for null.

> +		reset_control_assert(rstc);
> +		reset_control_deassert(rstc);

Is there any difference between:
reset_control_assert(rstc);
reset_control_assert(rstc_ocp);

reset_control_deassert(rstc);
reset_control_deassert(rstc_ocp);

and:

reset_control_assert(rstc);
reset_control_deassert(rstc);

reset_control_assert(rstc_ocp);
reset_control_deassert(rstc_ocp);

Which one would you choose?

Thanks, Dinh,
ta

> +
> +		if (rstc_ocp) {
> +			reset_control_assert(rstc_ocp);
> +			reset_control_deassert(rstc_ocp);
> +		}
> +	}
> +
>  	cqspi->master_ref_clk_hz = clk_get_rate(cqspi->clk);
>  	ddata  = of_device_get_match_data(dev);
>  	if (ddata && (ddata->quirks & CQSPI_NEEDS_WR_DELAY))
> 
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