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From: Serge Semin <Sergey.Semin@baikalelectronics.ru>
To: Mark Brown <broonie@kernel.org>
Cc: Serge Semin <Sergey.Semin@baikalelectronics.ru>,
	Serge Semin <fancer.lancer@gmail.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>,
	Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>,
	Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Arnd Bergmann <arnd@arndb.de>, Feng Tang <feng.tang@intel.com>,
	Rob Herring <robh+dt@kernel.org>, <linux-mips@vger.kernel.org>,
	<devicetree@vger.kernel.org>, <linux-spi@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>
Subject: [PATCH v6 08/16] spi: dw: Fix Rx-only DMA transfers
Date: Fri, 29 May 2020 16:11:57 +0300
Message-ID: <20200529131205.31838-9-Sergey.Semin@baikalelectronics.ru> (raw)
In-Reply-To: <20200529131205.31838-1-Sergey.Semin@baikalelectronics.ru>

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@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Cc: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.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 6939e003e3e9..4d1849699a12 100644
--- a/drivers/spi/spi-dw.c
+++ b/drivers/spi/spi-dw.c
@@ -515,6 +515,7 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
 			dev_warn(dev, "DMA init failed\n");
 		} else {
 			master->can_dma = dws->dma_ops->can_dma;
+			master->flags |= SPI_CONTROLLER_MUST_TX;
 		}
 	}
 
-- 
2.26.2


  parent reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-29 13:11 [PATCH v6 00/16] spi: dw: Add generic DW DMA controller support Serge Semin
2020-05-29 13:11 ` [PATCH v6 01/16] spi: dw: Set xfer effective_speed_hz Serge Semin
2020-05-29 13:11 ` [PATCH v6 02/16] spi: dw: Return any value retrieved from the dma_transfer callback Serge Semin
2020-05-29 13:11 ` [PATCH v6 03/16] spi: dw: Locally wait for the DMA transfers completion Serge Semin
2020-05-29 13:11 ` [PATCH v6 04/16] spi: dw: Add SPI Tx-done wait method to DMA-based transfer Serge Semin
2020-05-29 13:11 ` [PATCH v6 05/16] spi: dw: Add SPI Rx-done " Serge Semin
2020-05-29 13:11 ` [PATCH v6 06/16] spi: dw: Parameterize the DMA Rx/Tx burst length Serge Semin
2020-05-29 13:11 ` [PATCH v6 07/16] spi: dw: Use DMA max burst to set the request thresholds Serge Semin
2020-05-29 13:11 ` Serge Semin [this message]
2020-05-29 13:11 ` [PATCH v6 09/16] spi: dw: Add core suffix to the DW APB SSI core source file Serge Semin
2020-05-29 13:11 ` [PATCH v6 10/16] spi: dw: Move Non-DMA code to the DW PCIe-SPI driver Serge Semin
2020-05-29 13:12 ` [PATCH v6 11/16] spi: dw: Remove DW DMA code dependency from DW_DMAC_PCI Serge Semin
2020-05-29 13:12 ` [PATCH v6 12/16] spi: dw: Add DW SPI DMA/PCI/MMIO dependency on the DW SPI core Serge Semin
2020-05-29 13:12 ` [PATCH v6 13/16] spi: dw: Cleanup generic DW DMA code namings Serge Semin
2020-05-29 13:12 ` [PATCH v6 14/16] spi: dw: Add DMA support to the DW SPI MMIO driver Serge Semin
2020-05-29 13:12 ` [PATCH v6 15/16] spi: dw: Use regset32 DebugFS method to create regdump file Serge Semin
2020-05-29 13:12 ` [PATCH v6 16/16] dt-bindings: spi: Convert DW SPI binding to DT schema Serge Semin
2020-05-29 13:27 ` [PATCH v6 00/16] spi: dw: Add generic DW DMA controller support Andy Shevchenko
2020-05-29 17:18 ` Mark Brown
2020-05-29 17:26   ` Serge Semin
2020-05-29 17:33     ` Mark Brown
2020-05-29 17:35       ` Serge Semin
2020-05-29 21:22       ` Rob Herring
2020-05-29 22:21         ` Mark Brown
2020-05-29 17:43     ` Andy Shevchenko
2020-05-29 17:47       ` Serge Semin

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