Re: [PATCH V2 6/9] spi: bcm2835aux: warn in dmesg that native cs is not really supported
From: Stefan Wahren <hidden>
Date: 2019-03-25 10:28:31
Also in:
linux-spi
Hi Martin, Am 24.03.19 um 18:49 schrieb kernel@martin.sperl.org:
From: Martin Sperl <redacted> 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. Signed-off-by: Martin Sperl <redacted> Fixes: 1ea29b39f4c812ece2f936065a0a3d6fe44a263e
please use a proper fixes tag.
quoted hunk ↗ jump to hunk
--- drivers/spi/spi-bcm2835aux.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+)diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c index c8acde017b6a..6af07dec5fdc 100644 --- a/drivers/spi/spi-bcm2835aux.c +++ b/drivers/spi/spi-bcm2835aux.c@@ -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; + + if (spi->mode & SPI_NO_CS) + return 0; + /* sanity check for native cs */ + if (!gpio_is_valid(spi->cs_gpio)) { + /* 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... + */ + if (spi->chip_select == 0) { + dev_err(&spi->dev, + "native CS is not supported but may work for some use-cases for cs = 0 - please define a valid value cs-gpios in DT for complete feature set\n"); + return 0;
These messages are rather too long, please keep it in the ~ 80 char limit (in source code and dmesg). Or make it two lines ... Since we return with 0, i prefer to use dev_warn instead of dev_err. Thanks
+ } + dev_err(&spi->dev, + "native CS is not supported for cs > 0 - please define a valid value cs-gpios in DT to enable multiple cs\n"); + return -EINVAL; + } + + return 0; +} +
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