linux-kernel - Re: [PATCH v3 3/3] mtd: spi-nor: cadence-quadspi: disable the auto-poll for Intel LGM

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Date:   Wed, 16 Oct 2019 14:10:31 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     "Ramuthevar,Vadivel MuruganX" 
        <vadivel.muruganx.ramuthevar@...ux.intel.com>,
        <linux-mtd@...ts.infradead.org>
CC:     <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <dwmw2@...radead.org>, <computersforpeace@...il.com>,
        <richard@....at>, <jwboyer@...il.com>,
        <boris.brezillon@...e-electrons.com>, <cyrille.pitchen@...el.com>,
        <david.oberhollenzer@...ma-star.at>, <miquel.raynal@...tlin.com>,
        <tudor.ambarus@...il.com>, <andriy.shevchenko@...el.com>,
        <cheol.yong.kim@...el.com>, <qi-ming.wu@...el.com>
Subject: Re: [PATCH v3 3/3] mtd: spi-nor: cadence-quadspi: disable the
 auto-poll for Intel LGM



On 09/09/19 4:17 PM, Ramuthevar,Vadivel MuruganX wrote:
> From: Ramuthevar Vadivel Murugan <vadivel.muruganx.ramuthevar@...ux.intel.com>
> 
> On Intel's Lightning Mountain(LGM) SoC QSPI controller do not auto-poll.
> This patch introduces to properly disable the auto-polling feature to

This patch disables auto polling when direct access mode is disabled
which should be noted in the commit message.

> improve the performance of cadence-quadspi.

How does this improve performance of cadence-quadspi? I would expect HW
auto-polling to be faster than SW polling.

> 
> Signed-off-by: Ramuthevar Vadivel Murugan <vadivel.muruganx.ramuthevar@...ux.intel.com>
> ---
>  drivers/mtd/spi-nor/cadence-quadspi.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
> index 73b9fbd1508a..60998eaad1cc 100644
> --- a/drivers/mtd/spi-nor/cadence-quadspi.c
> +++ b/drivers/mtd/spi-nor/cadence-quadspi.c
> @@ -135,6 +135,8 @@ struct cqspi_driver_platdata {
>  #define CQSPI_REG_RD_INSTR_TYPE_DATA_MASK	0x3
>  #define CQSPI_REG_RD_INSTR_DUMMY_MASK		0x1F
>  
> +#define CQSPI_REG_WR_COMPLETION_CTRL		0x38
> +#define CQSPI_REG_WR_COMPLETION_DISABLE_AUTO_POLL	BIT(14)
>  #define CQSPI_REG_WR_INSTR			0x08
>  #define CQSPI_REG_WR_INSTR_OPCODE_LSB		0
>  #define CQSPI_REG_WR_INSTR_TYPE_ADDR_LSB	12
> @@ -471,6 +473,18 @@ static int cqspi_command_write_addr(struct spi_nor *nor,
>  	return cqspi_exec_flash_cmd(cqspi, reg);
>  }
>  
> +static int cqspi_disable_auto_poll(struct cqspi_st *cqspi)
> +{
> +	void __iomem *reg_base = cqspi->iobase;
> +	unsigned int reg;
> +
> +	reg = readl(reg_base + CQSPI_REG_WR_COMPLETION_CTRL);
> +	reg |= CQSPI_REG_WR_COMPLETION_DISABLE_AUTO_POLL;
> +	writel(reg, reg_base + CQSPI_REG_WR_COMPLETION_CTRL);
> +
> +	return 0;
> +}
> +
>  static int cqspi_read_setup(struct spi_nor *nor)
>  {
>  	struct cqspi_flash_pdata *f_pdata = nor->priv;
> @@ -508,6 +522,11 @@ static int cqspi_read_setup(struct spi_nor *nor)
>  	reg &= ~CQSPI_REG_SIZE_ADDRESS_MASK;
>  	reg |= (nor->addr_width - 1);
>  	writel(reg, reg_base + CQSPI_REG_SIZE);
> +
> +	/* Disable auto-polling */
> +	if (!f_pdata->use_direct_mode)
> +		cqspi_disable_auto_poll(cqspi);
> +
>  	return 0;
>  }
>  

Hmmm.. There is no need to disable polling for every read/write
operation. It should be enough to do it once in cqspi_controller_init()



> @@ -627,6 +646,11 @@ static int cqspi_write_setup(struct spi_nor *nor)
>  	reg &= ~CQSPI_REG_SIZE_ADDRESS_MASK;
>  	reg |= (nor->addr_width - 1);
>  	writel(reg, reg_base + CQSPI_REG_SIZE);
> +
> +	/* Disable auto-polling */
> +	if (!f_pdata->use_direct_mode)
> +		cqspi_disable_auto_poll(cqspi);
> +
>  	return 0;
>  }
>  
> 

-- 
Regards
Vignesh