From 509c583620e9053e43d611bf1614fc3d3abafa96 Mon Sep 17 00:00:00 2001 From: Martin Sperl Date: Sat, 30 Mar 2019 09:31:02 +0000 Subject: [PATCH] spi: bcm2835aux: fix driver to not allow 65535 (=-1) cs-gpios The original driver by default defines num_chipselects as -1. This actually allicates an array of 65535 entries in of_spi_register_master. There is a side-effect for buggy device trees that (contrary to dt-binding documentation) have no cs-gpio defined. This mode was never supported by the driver due to limitations of native cs and additional code complexity and is explicitly not stated to be implemented. To keep backwards compatibility with such buggy DTs we limit the number of chip_selects to 1, as for all practical purposes it is only ever realistic to use a single chip select in native cs mode without negative side-effects. Fixes: 1ea29b39f4c812ec ("spi: bcm2835aux: add bcm2835 auxiliary spi device...") Signed-off-by: Martin Sperl Acked-by: Stefan Wahren Signed-off-by: Mark Brown --- drivers/spi/spi-bcm2835aux.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c index 890aca4873a7..c8acde017b6a 100644 --- a/drivers/spi/spi-bcm2835aux.c +++ b/drivers/spi/spi-bcm2835aux.c @@ -413,7 +413,18 @@ static int bcm2835aux_spi_probe(struct platform_device *pdev) platform_set_drvdata(pdev, master); master->mode_bits = (SPI_CPOL | SPI_CS_HIGH | SPI_NO_CS); master->bits_per_word_mask = SPI_BPW_MASK(8); - master->num_chipselect = -1; + /* even though the driver never officially supported native CS + * allow a single native CS for legacy DT support purposes when + * no cs-gpio is configured. + * Known limitations for native cs are: + * * multiple chip-selects: cs0-cs2 are all simultaniously asserted + * whenever there is a transfer - this even includes SPI_NO_CS + * * SPI_CS_HIGH: is ignores - 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 + * a spi_transfer + */ + master->num_chipselect = 1; master->transfer_one = bcm2835aux_spi_transfer_one; master->handle_err = bcm2835aux_spi_handle_err; master->prepare_message = bcm2835aux_spi_prepare_message; -- 2.30.2