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From a223a36225da82a734ccd156c622e76507b4831e Mon Sep 17 00:00:00 2001 |
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From: Linus Walleij <linus.walleij@linaro.org> |
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Date: Mon, 10 Sep 2018 00:28:05 +0200 |
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Subject: [PATCH 060/145] spi: gpio: No MISO does not imply no RX |
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|
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[ Upstream commit abf5feef3ff0cefade0c76be53b59e55fdd46093 ] |
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|
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There is a logical problem in spi-gpio with host just |
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assigning a MOSI line and no MISO: this is interpreted |
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as the host cannot do RX and the host is flagged with |
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SPI_MASTER_NO_RX. |
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|
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This is wrong: since GPIO lines can switch direction, |
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in 3WIRE operation the host will simply reverse the |
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direction of the GPIO line and start reading from it, |
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there is even code for doing this in the driver, but |
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it went unnoticed because it was tested by using a |
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master with 4 wires but a device using just 3 wires. |
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|
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Remove the offending flag. |
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|
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Cc: Andrzej Hajda <a.hajda@samsung.com> |
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Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com> |
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Signed-off-by: Linus Walleij <linus.walleij@linaro.org> |
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Signed-off-by: Mark Brown <broonie@kernel.org> |
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Signed-off-by: Sasha Levin <sashal@kernel.org> |
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--- |
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drivers/spi/spi-gpio.c | 10 ++++++---- |
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1 file changed, 6 insertions(+), 4 deletions(-) |
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|
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diff --git a/drivers/spi/spi-gpio.c b/drivers/spi/spi-gpio.c |
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index 421bfc7dda67..088772ebef9b 100644 |
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--- a/drivers/spi/spi-gpio.c |
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+++ b/drivers/spi/spi-gpio.c |
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@@ -295,9 +295,11 @@ static int spi_gpio_request(struct device *dev, |
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spi_gpio->miso = devm_gpiod_get_optional(dev, "miso", GPIOD_IN); |
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if (IS_ERR(spi_gpio->miso)) |
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return PTR_ERR(spi_gpio->miso); |
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- if (!spi_gpio->miso) |
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- /* HW configuration without MISO pin */ |
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- *mflags |= SPI_MASTER_NO_RX; |
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+ /* |
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+ * No setting SPI_MASTER_NO_RX here - if there is only a MOSI |
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+ * pin connected the host can still do RX by changing the |
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+ * direction of the line. |
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+ */ |
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|
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spi_gpio->sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW); |
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if (IS_ERR(spi_gpio->sck)) |
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@@ -423,7 +425,7 @@ static int spi_gpio_probe(struct platform_device *pdev) |
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spi_gpio->bitbang.chipselect = spi_gpio_chipselect; |
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spi_gpio->bitbang.set_line_direction = spi_gpio_set_direction; |
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|
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- if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) { |
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+ if ((master_flags & SPI_MASTER_NO_TX) == 0) { |
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spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0; |
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spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1; |
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spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2; |
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-- |
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2.19.1 |
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