linux-kernel - Re: [PATCH 06/11] spi: dw: update SPI

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Date:   Sat, 27 Aug 2022 01:50:09 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Sudip Mukherjee <sudip.mukherjee@...ive.com>
Cc:     Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        greentime.hu@...ive.com, jude.onyenegecha@...ive.com,
        william.salmon@...ive.com, adnan.chowdhury@...ive.com,
        ben.dooks@...ive.com, linux-spi@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        jeegar.lakhani@...ive.com
Subject: Re: [PATCH 06/11] spi: dw: update SPI_CTRLR0 register

On Tue, Aug 02, 2022 at 06:57:50PM +0100, Sudip Mukherjee wrote:
> If the controller supports enhanced SPI modes then update the register
> or reset the register if the transfer is not using dual/quad/octal mode.
> 
> Signed-off-by: Sudip Mukherjee <sudip.mukherjee@...ive.com>
> ---
>  drivers/spi/spi-dw-core.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
> index 8e624620864f..9d499bdf2ce6 100644
> --- a/drivers/spi/spi-dw-core.c
> +++ b/drivers/spi/spi-dw-core.c
> @@ -676,6 +676,32 @@ static void dw_spi_stop_mem_op(struct dw_spi *dws, struct spi_device *spi)
>  	dw_spi_enable_chip(dws, 1);
>  }
>  
> +static void update_spi_ctrl0(struct dw_spi *dws, const struct spi_mem_op *op, bool enable)
> +{
> +	u32 spi_ctrlr0;
> +
> +	spi_ctrlr0 = dw_readl(dws, DW_HSSI_SPI_CTRLR0);
> +	if (enable) {
> +		spi_ctrlr0 |= FIELD_PREP(DW_HSSI_SPI_CTRLR0_WAIT_CYCLE_MASK,

> +					 op->dummy.nbytes * BITS_PER_BYTE);
> +		/* 8 bit instruction length */
> +		spi_ctrlr0 |= FIELD_PREP(DW_HSSI_SPI_CTRLR0_INST_L_MASK,
> +					 DW_HSSI_SPI_CTRLR0_INST_L8);
> +		/* 32 bit address length */
> +		spi_ctrlr0 |= FIELD_PREP(DW_HSSI_SPI_CTRLR0_ADDR_L_MASK,
> +					 DW_HSSI_SPI_CTRLR0_ADDR_L32);

Just add new fields dw_spi_cfg.{trans_t,inst_l,addr_l,wait_c},
initialize them with the values taken from the spi_mem_op (trans_t -
based on the bus widths, inst_l - cmd.nbytes, addr_l - addr.nbytes,
wait_c - dummy.nbytes / dummy.buswidth) and use them to accordingly
update the SPI_CTRLR0 CSR in the dw_spi_update_config() method. Update
the CSR if spi_frf has value other than STD_SPI_FRF, otherwise
according to the HW manual the SPI_CTRLR0 register isn't relevant so
don't touch it.

> +		/* Enable clock stretching */
> +		spi_ctrlr0 |= DW_HSSI_SPI_CTRLR0_CLK_STRETCH_EN;
> +	} else {
> +		spi_ctrlr0 &= ~DW_HSSI_SPI_CTRLR0_WAIT_CYCLE_MASK;
> +		spi_ctrlr0 &= ~DW_HSSI_SPI_CTRLR0_INST_L_MASK;
> +		spi_ctrlr0 &= ~DW_HSSI_SPI_CTRLR0_ADDR_L_MASK;
> +		spi_ctrlr0 &= ~DW_HSSI_SPI_CTRLR0_CLK_STRETCH_EN;
> +	}
> +
> +	dw_writel(dws, DW_HSSI_SPI_CTRLR0, spi_ctrlr0);
> +}
> +
>  /*
>   * The SPI memory operation implementation below is the best choice for the
>   * devices, which are selected by the native chip-select lane. It's
> @@ -738,6 +764,9 @@ static int dw_spi_exec_mem_op(struct spi_mem *mem, const struct spi_mem_op *op)
>  
>  	dw_spi_enable_chip(dws, 0);
>  

> +	if (dws->caps & DW_SPI_CAP_EXT_SPI)
> +		update_spi_ctrl0(dws, op, enhanced_spi);
> +

This won't be needed as long as you do as I suggested above.

-Sergey

>  	dw_spi_update_config(dws, mem->spi, &cfg);
>  
>  	dw_spi_mask_intr(dws, 0xff);
> -- 
> 2.30.2
>