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

Lars Povlsen
2020-06-09T09:14:03Z

Serge Semin writes:

> 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.
>

Yeah, but with the poll_transfer() gone below, I think I'll settle on
just getting this into the current framework. Optimization (as this is)
has less priority. I'll put this on the back burner.

>> +
>> /* 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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>> linux-arm-kernel@lists.infradead.org
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--
Lars Povlsen,
Microchip