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Message-Id: <20200608231848.3366970-56-sashal@kernel.org>
Date: Mon, 8 Jun 2020 19:16:49 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Serge Semin <Sergey.Semin@...kalelectronics.ru>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Georgy Vlasov <Georgy.Vlasov@...kalelectronics.ru>,
Ramil Zaripov <Ramil.Zaripov@...kalelectronics.ru>,
Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Arnd Bergmann <arnd@...db.de>, Feng Tang <feng.tang@...el.com>,
Rob Herring <robh+dt@...nel.org>, linux-mips@...r.kernel.org,
devicetree@...r.kernel.org, Mark Brown <broonie@...nel.org>,
Sasha Levin <sashal@...nel.org>, linux-spi@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 056/175] spi: dw: Fix Rx-only DMA transfers
From: Serge Semin <Sergey.Semin@...kalelectronics.ru>
[ Upstream commit 46164fde6b7890e7a3982d54549947c8394c0192 ]
Tx-only DMA transfers are working perfectly fine since in this case
the code just ignores the Rx FIFO overflow interrupts. But it turns
out the SPI Rx-only transfers are broken since nothing pushing any
data to the shift registers, so the Rx FIFO is left empty and the
SPI core subsystems just returns a timeout error. Since DW DMAC
driver doesn't support something like cyclic write operations of
a single byte to a device register, the only way to support the
Rx-only SPI transfers is to fake it by using a dummy Tx-buffer.
This is what we intend to fix in this commit by setting the
SPI_CONTROLLER_MUST_TX flag for DMA-capable platform.
Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Georgy Vlasov <Georgy.Vlasov@...kalelectronics.ru>
Cc: Ramil Zaripov <Ramil.Zaripov@...kalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Feng Tang <feng.tang@...el.com>
Cc: Rob Herring <robh+dt@...nel.org>
Cc: linux-mips@...r.kernel.org
Cc: devicetree@...r.kernel.org
Link: https://lore.kernel.org/r/20200529131205.31838-9-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
drivers/spi/spi-dw.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
index 11cac7e10663..8a4438f4c954 100644
--- a/drivers/spi/spi-dw.c
+++ b/drivers/spi/spi-dw.c
@@ -518,6 +518,7 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
dws->dma_inited = 0;
} else {
master->can_dma = dws->dma_ops->can_dma;
+ master->flags |= SPI_CONTROLLER_MUST_TX;
}
}
--
2.25.1
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