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

Serge Semin
2020-06-02T19:10:40Z

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@bootlin.com>
> Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
> ---
> 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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