Re: [PATCH 01/10] spi: dw: Add support for polled operation via no IRQ specified in DT

[Serge Semin]

On Wed, May 13, 2020 at 04:00:22PM +0200, Lars Povlsen wrote:
> With this change a SPI controller can be added without having a IRQ
> associated, and causing all transfers to be polled. For SPI controllers
> without DMA, this can significantly improve performance by less
> interrupt handling overhead.
> 
> Reviewed-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
> Signed-off-by: Lars Povlsen <lars.povlsen@xxxxxxxxxxxxx>
> ---
>  drivers/spi/spi-dw.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
> index 31e3f866d11a7..e572eb34a3c1a 100644
> --- a/drivers/spi/spi-dw.c
> +++ b/drivers/spi/spi-dw.c
> @@ -19,6 +19,8 @@
>  #include <linux/debugfs.h>
>  #endif
> 

> +#define VALID_IRQ(i) (i >= 0)

Mark and Andy are right. It is a good candidate to be in a generic IRQ-related
code as Anyd suggested:

> > drivers/rtc/rtc-cmos.c:95:#define is_valid_irq(n)               ((n) > 0)
> > Candidate to be in include/linux/irq.h ?

So if you feel like to author additional useful patch integrated into the
kernel, this one is a good chance for it.

> +
>  /* Slave spi_dev related */
>  struct chip_data {
>  	u8 tmode;		/* TR/TO/RO/EEPROM */
> @@ -359,7 +361,7 @@ static int dw_spi_transfer_one(struct spi_controller *master,
>  			spi_enable_chip(dws, 1);
>  			return ret;
>  		}
> -	} else if (!chip->poll_mode) {
> +	} else if (!chip->poll_mode && VALID_IRQ(dws->irq)) {
>  		txlevel = min_t(u16, dws->fifo_len / 2, dws->len / dws->n_bytes);
>  		dw_writel(dws, DW_SPI_TXFLTR, txlevel);
> 
> @@ -379,7 +381,7 @@ static int dw_spi_transfer_one(struct spi_controller *master,
>  			return ret;
>  	}
> 
> -	if (chip->poll_mode)
> +	if (chip->poll_mode || !VALID_IRQ(dws->irq))
>  		return poll_transfer(dws);

Please note. The chip->poll and the poll_transfer() methods've been discarded
from the driver, since commit 1ceb09717e98 ("spi: dw: remove cs_control and
poll_mode members from chip_data"). So you gonna have to get the
poll_transfer-like method back.

-Sergey

> 
>  	return 1;
> @@ -487,11 +489,13 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
> 
>  	spi_controller_set_devdata(master, dws);
> 
> -	ret = request_irq(dws->irq, dw_spi_irq, IRQF_SHARED, dev_name(dev),
> -			  master);
> -	if (ret < 0) {
> -		dev_err(dev, "can not get IRQ\n");
> -		goto err_free_master;
> +	if (VALID_IRQ(dws->irq)) {
> +		ret = request_irq(dws->irq, dw_spi_irq, IRQF_SHARED,
> +				  dev_name(dev), master);
> +		if (ret < 0) {
> +			dev_err(dev, "can not get IRQ\n");
> +			goto err_free_master;
> +		}
>  	}
> 
>  	master->use_gpio_descriptors = true;
> @@ -539,7 +543,8 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
>  	if (dws->dma_ops && dws->dma_ops->dma_exit)
>  		dws->dma_ops->dma_exit(dws);
>  	spi_enable_chip(dws, 0);
> -	free_irq(dws->irq, master);
> +	if (VALID_IRQ(dws->irq))
> +		free_irq(dws->irq, master);
>  err_free_master:
>  	spi_controller_put(master);
>  	return ret;
> --
> 2.26.2
> 
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