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spi: bcm2835aux: warn in dmesg that native cs is not really supported 

From personal bad experience (even as the author of the original driver)
it shows that native-cs is "somewhat" supported by the spi bus driver
when using a buggy device tree.

So make sure that the driver is warning in dmesg about this fact
that we are running in a not supported mode that may have surprizing
limitations.

Fixes: 1ea29b39f4 ("spi: bcm2835aux: add bcm2835 auxiliary spi device...")
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Martin Sperl 2019-03-30 09:31:03 +00:00 committed by Mark Brown
parent 509c583620
commit 519f2c22a6
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GPG Key ID: 24D68B725D5487D0
1 changed files with 33 additions and 0 deletions
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33
drivers/spi/spi-bcm2835aux.c
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@ -396,6 +396,38 @@ static void bcm2835aux_spi_handle_err(struct spi_master *master,
bcm2835aux_spi_reset_hw(bs);
}
static int bcm2835aux_spi_setup(struct spi_device *spi)
{
int ret;
/* sanity check for native cs */
if (spi->mode & SPI_NO_CS)
return 0;
if (gpio_is_valid(spi->cs_gpio))
return 0;
/* for dt-backwards compatibility: only support native on CS0
* known things not supported with broken native CS:
* * multiple chip-selects: cs0-cs2 are all
* simultaniously asserted whenever there is a transfer
* this even includes SPI_NO_CS
* * SPI_CS_HIGH: cs are always asserted low
* * cs_change: cs is deasserted after each spi_transfer
* * cs_delay_usec: cs is always deasserted one SCK cycle
* after the last transfer
* probably more...
*/
dev_warn(&spi->dev,
"Native CS is not supported - please configure cs-gpio in device-tree\n");
if (spi->chip_select == 0)
return 0;
dev_warn(&spi->dev, "Native CS is not working for cs > 0\n");
return -EINVAL;
}
static int bcm2835aux_spi_probe(struct platform_device *pdev)
{
struct spi_master *master;
@ -425,6 +457,7 @@ static int bcm2835aux_spi_probe(struct platform_device *pdev)
* a spi_transfer
*/
master->num_chipselect = 1;
master->setup = bcm2835aux_spi_setup;
master->transfer_one = bcm2835aux_spi_transfer_one;
master->handle_err = bcm2835aux_spi_handle_err;
master->prepare_message = bcm2835aux_spi_prepare_message;