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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>,
	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 07/16] spi: dw: Use DMA max burst to set the request thresholds
Date: Fri, 29 May 2020 16:11:56 +0300
Message-ID: <20200529131205.31838-8-Sergey.Semin@baikalelectronics.ru> (raw)
In-Reply-To: <20200529131205.31838-1-Sergey.Semin@baikalelectronics.ru>

Each channel of DMA controller may have a limited length of burst
transaction (number of IO operations performed at ones in a single
DMA client request). This parameter can be used to setup the most
optimal DMA Tx/Rx data level values. In order to avoid the Tx buffer
overrun we can set the DMA Tx level to be of FIFO depth minus the
maximum burst transactions length. To prevent the Rx buffer underflow
the DMA Rx level should be set to the maximum burst transactions length.
This commit setups the DMA channels and the DW SPI DMA Tx/Rx levels
in accordance with these rules.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
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

---

Changelog v3:
- Use min() method to calculate the optimal burst values.
---
 drivers/spi/spi-dw-mid.c | 37 +++++++++++++++++++++++++++++++++----
 drivers/spi/spi-dw.h     |  2 ++
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-dw-mid.c b/drivers/spi/spi-dw-mid.c
index 189b517f77fc..1cf9e3ffe07b 100644
--- a/drivers/spi/spi-dw-mid.c
+++ b/drivers/spi/spi-dw-mid.c
@@ -36,6 +36,31 @@ static bool mid_spi_dma_chan_filter(struct dma_chan *chan, void *param)
 	return true;
 }
 
+static void mid_spi_maxburst_init(struct dw_spi *dws)
+{
+	struct dma_slave_caps caps;
+	u32 max_burst, def_burst;
+	int ret;
+
+	def_burst = dws->fifo_len / 2;
+
+	ret = dma_get_slave_caps(dws->rxchan, &caps);
+	if (!ret && caps.max_burst)
+		max_burst = caps.max_burst;
+	else
+		max_burst = RX_BURST_LEVEL;
+
+	dws->rxburst = min(max_burst, def_burst);
+
+	ret = dma_get_slave_caps(dws->txchan, &caps);
+	if (!ret && caps.max_burst)
+		max_burst = caps.max_burst;
+	else
+		max_burst = TX_BURST_LEVEL;
+
+	dws->txburst = min(max_burst, def_burst);
+}
+
 static int mid_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
 {
 	struct dw_dma_slave slave = {
@@ -73,6 +98,8 @@ static int mid_spi_dma_init_mfld(struct device *dev, struct dw_spi *dws)
 
 	init_completion(&dws->dma_completion);
 
+	mid_spi_maxburst_init(dws);
+
 	return 0;
 
 free_rxchan:
@@ -100,6 +127,8 @@ static int mid_spi_dma_init_generic(struct device *dev, struct dw_spi *dws)
 
 	init_completion(&dws->dma_completion);
 
+	mid_spi_maxburst_init(dws);
+
 	return 0;
 }
 
@@ -229,7 +258,7 @@ static struct dma_async_tx_descriptor *dw_spi_dma_prepare_tx(struct dw_spi *dws,
 	memset(&txconf, 0, sizeof(txconf));
 	txconf.direction = DMA_MEM_TO_DEV;
 	txconf.dst_addr = dws->dma_addr;
-	txconf.dst_maxburst = TX_BURST_LEVEL;
+	txconf.dst_maxburst = dws->txburst;
 	txconf.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
 	txconf.dst_addr_width = convert_dma_width(dws->n_bytes);
 	txconf.device_fc = false;
@@ -321,7 +350,7 @@ static struct dma_async_tx_descriptor *dw_spi_dma_prepare_rx(struct dw_spi *dws,
 	memset(&rxconf, 0, sizeof(rxconf));
 	rxconf.direction = DMA_DEV_TO_MEM;
 	rxconf.src_addr = dws->dma_addr;
-	rxconf.src_maxburst = RX_BURST_LEVEL;
+	rxconf.src_maxburst = dws->rxburst;
 	rxconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
 	rxconf.src_addr_width = convert_dma_width(dws->n_bytes);
 	rxconf.device_fc = false;
@@ -346,8 +375,8 @@ static int mid_spi_dma_setup(struct dw_spi *dws, struct spi_transfer *xfer)
 {
 	u16 imr = 0, dma_ctrl = 0;
 
-	dw_writel(dws, DW_SPI_DMARDLR, RX_BURST_LEVEL - 1);
-	dw_writel(dws, DW_SPI_DMATDLR, TX_BURST_LEVEL);
+	dw_writel(dws, DW_SPI_DMARDLR, dws->rxburst - 1);
+	dw_writel(dws, DW_SPI_DMATDLR, dws->fifo_len - dws->txburst);
 
 	if (xfer->tx_buf) {
 		dma_ctrl |= SPI_DMA_TDMAE;
diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h
index 9585d0c83a6d..9247670fcdfb 100644
--- a/drivers/spi/spi-dw.h
+++ b/drivers/spi/spi-dw.h
@@ -142,7 +142,9 @@ struct dw_spi {
 
 	/* DMA info */
 	struct dma_chan		*txchan;
+	u32			txburst;
 	struct dma_chan		*rxchan;
+	u32			rxburst;
 	unsigned long		dma_chan_busy;
 	dma_addr_t		dma_addr; /* phy address of the Data register */
 	const struct dw_spi_dma_ops *dma_ops;
-- 
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 ` Serge Semin [this message]
2020-05-29 13:11 ` [PATCH v6 08/16] spi: dw: Fix Rx-only DMA transfers Serge Semin
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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