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SubjectRe: [PATCH v2 1/1] spi: Assume GPIO CS active high in ACPI case
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在 2021/5/11 下午10:09, Andy Shevchenko 写道:
> Currently GPIO CS handling, when descriptors are in use, doesn't
> take into consideration that in ACPI case the default polarity
> is Active High and can't be altered. Instead we have to use the
> per-chip definition provided by SPISerialBus() resource.
>
> Fixes: 766c6b63aa04 ("spi: fix client driver breakages when using GPIO descriptors")
> Cc: Liguang Zhang <zhangliguang@linux.alibaba.com>
> Cc: Jay Fang <f.fangjian@huawei.com>
> Cc: Sven Van Asbroeck <thesven73@gmail.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Tested-by: Xin Hao <xhao@linux.alibaba.com>
> ---
> v2: refactor to avoid ternary (Mark, Sven), dropped comment changes (Mark)
> drivers/spi/spi.c | 22 ++++++++++++++++++----
> 1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index cd40421b8f55..36ee33514b40 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -820,15 +820,29 @@ static void spi_set_cs(struct spi_device *spi, bool enable, bool force)
>
> if (spi->cs_gpiod || gpio_is_valid(spi->cs_gpio)) {
> if (!(spi->mode & SPI_NO_CS)) {
> - if (spi->cs_gpiod)
> - /* polarity handled by gpiolib */
> - gpiod_set_value_cansleep(spi->cs_gpiod, activate);
> - else
> + if (spi->cs_gpiod) {
> + /*
> + * Historically ACPI has no means of the GPIO polarity and
> + * thus the SPISerialBus() resource defines it on the per-chip
> + * basis. In order to avoid a chain of negations, the GPIO
> + * polarity is considered being Active High. Even for the cases
> + * when _DSD() is involved (in the updated versions of ACPI)
> + * the GPIO CS polarity must be defined Active High to avoid
> + * ambiguity. That's why we use enable, that takes SPI_CS_HIGH
> + * into account.
> + */
> + if (has_acpi_companion(&spi->dev))
> + gpiod_set_value_cansleep(spi->cs_gpiod, !enable);

it worked and code changed minimally,  before ACPI & OF keeps no same
rules,  this patch is ok!

> + else
> + /* Polarity handled by GPIO library */
> + gpiod_set_value_cansleep(spi->cs_gpiod, activate);
> + } else {
> /*
> * invert the enable line, as active low is
> * default for SPI.
> */
> gpio_set_value_cansleep(spi->cs_gpio, !enable);
> + }
> }
> /* Some SPI masters need both GPIO CS & slave_select */
> if ((spi->controller->flags & SPI_MASTER_GPIO_SS) &&

--
Best Regards!
Xin Hao

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