linux-kernel - Re: [PATCH v2 09/15] spi: dw: use irq handler for enhanced spi

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Date:   Tue, 10 Jan 2023 15:08:25 +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>,
        jude.onyenegecha@...ive.com, ben.dooks@...ive.com,
        jeegar.lakhani@...ive.com, linux-spi@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 09/15] spi: dw: use irq handler for enhanced spi

On Mon, Dec 12, 2022 at 06:07:26PM +0000, Sudip Mukherjee wrote:
> Introduce the interrupt handler for enhanced spi to read or write based
> on the generated irq. Also, use the xfer_completion from spi_controller
> to wait for a timeout or completion from irq handler.
> 
> Signed-off-by: Sudip Mukherjee <sudip.mukherjee@...ive.com>
> ---
>  drivers/spi/spi-dw-core.c | 62 ++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 61 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
> index f540165245a89..10d453228368f 100644
> --- a/drivers/spi/spi-dw-core.c
> +++ b/drivers/spi/spi-dw-core.c
> @@ -251,6 +251,34 @@ static irqreturn_t dw_spi_transfer_handler(struct dw_spi *dws)
>  	return IRQ_HANDLED;
>  }
>  
> +static irqreturn_t dw_spi_enh_handler(struct dw_spi *dws)
> +{
> +	u16 irq_status = dw_readl(dws, DW_SPI_ISR);
> +
> +	if (dw_spi_check_status(dws, false)) {

> +		spi_finalize_current_transfer(dws->master);

As I suggested in the cover-letter please use the dw_spi_dma_wait()
function for that.

> +		return IRQ_HANDLED;
> +	}
> +
> +	if (irq_status & DW_SPI_INT_RXFI) {
> +		dw_reader(dws);
> +		if (dws->rx_len <= dw_readl(dws, DW_SPI_RXFTLR))
> +			dw_writel(dws, DW_SPI_RXFTLR, dws->rx_len - 1);
> +	}
> +
> +	if (irq_status & DW_SPI_INT_TXEI)
> +		dw_writer(dws);
> +

> +	if (!dws->tx_len && dws->rx_len) {
> +		dw_spi_mask_intr(dws, DW_SPI_INT_TXEI);
> +	} else if (!dws->rx_len && !dws->tx_len) {
> +		dw_spi_mask_intr(dws, 0xff);
> +		spi_finalize_current_transfer(dws->master);

Why so complicated? You have two types of the transfers: Tx-only and
Rx-only. Thus you can unmask only one type of the IRQs and terminate
the process upon both lengths are zero.

> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static irqreturn_t dw_spi_irq(int irq, void *dev_id)
>  {
>  	struct spi_controller *master = dev_id;
> @@ -265,6 +293,12 @@ static irqreturn_t dw_spi_irq(int irq, void *dev_id)
>  		dw_spi_mask_intr(dws, 0xff);
>  		return IRQ_HANDLED;
>  	}

> +	if ((dws->transfer_handler == dw_spi_enh_handler &&
> +	     !dws->rx_len && !dws->tx_len)) {
> +		dw_spi_mask_intr(dws, 0xff);
> +		spi_finalize_current_transfer(master);
> +		return IRQ_HANDLED;

Why? You already have this statement in the handler above.

> +	}
>  
>  	return dws->transfer_handler(dws);
>  }
> @@ -862,6 +896,8 @@ static int dw_spi_exec_enh_mem_op(struct spi_mem *mem, const struct spi_mem_op *
>  	struct spi_controller *ctlr = mem->spi->controller;
>  	struct dw_spi *dws = spi_controller_get_devdata(ctlr);
>  	struct dw_spi_cfg cfg;
> +	int ret = 0;
> +	unsigned long long ms;
>  
>  	switch (op->data.buswidth) {
>  	case 2:
> @@ -909,11 +945,35 @@ static int dw_spi_exec_enh_mem_op(struct spi_mem *mem, const struct spi_mem_op *
>  
>  	dw_spi_update_config(dws, mem->spi, &cfg);
>  
> +	dw_spi_mask_intr(dws, 0xff);
> +	reinit_completion(&ctlr->xfer_completion);
>  	dw_spi_enable_chip(dws, 1);
>  
>  	dw_spi_enh_write_cmd_addr(dws, op);
> +	dw_spi_set_cs(mem->spi, false);
> +	dw_spi_irq_setup(dws, dw_spi_enh_handler);
>  
> -	return 0;

> +	/* Use timeout calculation from spi_transfer_wait() */
> +	ms = 8LL * MSEC_PER_SEC * (dws->rx_len ? dws->rx_len : dws->tx_len);
> +	do_div(ms, dws->current_freq);
> +
> +	/*
> +	 * Increase it twice and add 200 ms tolerance, use
> +	 * predefined maximum in case of overflow.
> +	 */
> +	ms += ms + 200;
> +	if (ms > UINT_MAX)
> +		ms = UINT_MAX;
> +
> +	ms = wait_for_completion_timeout(&ctlr->xfer_completion,
> +					 msecs_to_jiffies(ms));

All of that is already implemented in the dw_spi_dma_wait() method.
Moreover addr+cmd write procedure, IRQ setup and wait-for-completion
can be consolidate in the dw_spi_enh_write_then_read() function thus
having the dw_spi_enh_exec_mem_op method looking similar to the
standard dw_spi_exec_mem_op().

-Serge(y)

> +
> +	dw_spi_stop_mem_op(dws, mem->spi);
> +
> +	if (ms == 0)
> +		ret = -EIO;
> +
> +	return ret;
>  }
>  
>  /*
> -- 
> 2.30.2
>