linux-kernel - Re: [PATCH v3 2/5] mtd: spi-nor: cadence-quadspi: add a delay in write sequence

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Date:   Sun, 24 Sep 2017 13:59:45 +0200
From:   Marek Vasut <marek.vasut@...il.com>
To:     Vignesh R <vigneshr@...com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 2/5] mtd: spi-nor: cadence-quadspi: add a delay in
 write sequence

On 09/24/2017 12:59 PM, Vignesh R wrote:
> As per 66AK2G02 TRM[1] SPRUHY8F section 11.15.5.3 Indirect Access
> Controller programming sequence, a delay equal to couple of QSPI master
> clock(~5ns) is required after setting CQSPI_REG_INDIRECTWR_START bit and
> writing data to the flash. Introduce a quirk flag CQSPI_NEEDS_WR_DELAY
> to handle this and set this flag for TI 66AK2G SoC.
> 
> [1]http://www.ti.com/lit/ug/spruhy8f/spruhy8f.pdf
> 
> Signed-off-by: Vignesh R <vigneshr@...com>

Is this TI specific or is this controller property ? I wouldn't be
surprised of the later ...

> ---
> 
> v3:
> Fix build warnings reported by kbuild test bot.
> 
>  drivers/mtd/spi-nor/cadence-quadspi.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
> index 53c7d8e0327a..5cd5d6f7303f 100644
> --- a/drivers/mtd/spi-nor/cadence-quadspi.c
> +++ b/drivers/mtd/spi-nor/cadence-quadspi.c
> @@ -38,6 +38,9 @@
>  #define CQSPI_NAME			"cadence-qspi"
>  #define CQSPI_MAX_CHIPSELECT		16
>  
> +/* Quirks */
> +#define CQSPI_NEEDS_WR_DELAY		BIT(0)
> +
>  struct cqspi_st;
>  
>  struct cqspi_flash_pdata {
> @@ -76,6 +79,7 @@ struct cqspi_st {
>  	u32			fifo_depth;
>  	u32			fifo_width;
>  	u32			trigger_address;
> +	u32			wr_delay;
>  	struct cqspi_flash_pdata f_pdata[CQSPI_MAX_CHIPSELECT];
>  };
>  
> @@ -608,6 +612,15 @@ static int cqspi_indirect_write_execute(struct spi_nor *nor,
>  	reinit_completion(&cqspi->transfer_complete);
>  	writel(CQSPI_REG_INDIRECTWR_START_MASK,
>  	       reg_base + CQSPI_REG_INDIRECTWR);
> +	/*
> +	 * As per 66AK2G02 TRM SPRUHY8F section 11.15.5.3 Indirect Access
> +	 * Controller programming sequence, couple of cycles of
> +	 * QSPI_REF_CLK delay is required for the above bit to
> +	 * be internally synchronized by the QSPI module. Provide 5
> +	 * cycles of delay.
> +	 */
> +	if (cqspi->wr_delay)
> +		ndelay(cqspi->wr_delay);
>  
>  	while (remaining > 0) {
>  		write_bytes = remaining > page_size ? page_size : remaining;
> @@ -1156,6 +1169,7 @@ static int cqspi_probe(struct platform_device *pdev)
>  	struct cqspi_st *cqspi;
>  	struct resource *res;
>  	struct resource *res_ahb;
> +	unsigned long data;
>  	int ret;
>  	int irq;
>  
> @@ -1213,6 +1227,10 @@ static int cqspi_probe(struct platform_device *pdev)
>  	}
>  
>  	cqspi->master_ref_clk_hz = clk_get_rate(cqspi->clk);
> +	data  = (unsigned long)of_device_get_match_data(dev);
> +	if (data & CQSPI_NEEDS_WR_DELAY)
> +		cqspi->wr_delay = 5 * DIV_ROUND_UP(NSEC_PER_SEC,
> +						   cqspi->master_ref_clk_hz);
>  
>  	ret = devm_request_irq(dev, irq, cqspi_irq_handler, 0,
>  			       pdev->name, cqspi);
> @@ -1284,7 +1302,14 @@ static const struct dev_pm_ops cqspi__dev_pm_ops = {
>  #endif
>  
>  static const struct of_device_id cqspi_dt_ids[] = {
> -	{.compatible = "cdns,qspi-nor",},
> +	{
> +		.compatible = "cdns,qspi-nor",
> +		.data = (void *)0,
> +	},
> +	{
> +		.compatible = "ti,k2g-qspi",
> +		.data = (void *)CQSPI_NEEDS_WR_DELAY,
> +	},
>  	{ /* end of table */ }
>  };
>  
> 


-- 
Best regards,
Marek Vasut