spi: pxa2xx: Use dummy buffers provided by SPI core

Dummy buffer is used for half duplex transfers that don't have TX or RX
buffer set. Instead of own dummy buffer management here let the SPI core to
handle it by setting the SPI_MASTER_MUST_RX and SPI_MASTER_MUST_TX flags.
Then core makes sure both transfer buffers are set.
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-pxa2xx-dma.c

@@ -53,11 +53,7 @@ static int pxa2xx_spi_map_dma_buffer(struct driver_data *drv_data,
 	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
 		size_t bytes = min_t(size_t, len, SZ_2K);
 
-		if (buf)
-			sg_set_buf(sg, pbuf, bytes);
-		else
-			sg_set_buf(sg, drv_data->dummy, bytes);
-
+		sg_set_buf(sg, pbuf, bytes);
 		pbuf += bytes;
 		len -= bytes;
 	}
@@ -312,10 +308,6 @@ int pxa2xx_spi_dma_setup(struct driver_data *drv_data)
 	dma_cap_zero(mask);
 	dma_cap_set(DMA_SLAVE, mask);
 
-	drv_data->dummy = devm_kzalloc(dev, SZ_2K, GFP_KERNEL);
-	if (!drv_data->dummy)
-		return -ENOMEM;
-
 	drv_data->tx_chan = dma_request_slave_channel_compat(mask,
 				pdata->dma_filter, pdata->tx_param, dev, "tx");
 	if (!drv_data->tx_chan)

drivers/spi/spi-pxa2xx.c

@@ -1562,6 +1562,7 @@ static int pxa2xx_spi_probe(struct platform_device *pdev)
 	master->unprepare_transfer_hardware = pxa2xx_spi_unprepare_transfer;
 	master->fw_translate_cs = pxa2xx_spi_fw_translate_cs;
 	master->auto_runtime_pm = true;
+	master->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX;
 
 	drv_data->ssp_type = ssp->type;
 

drivers/spi/spi-pxa2xx.h

@@ -56,7 +56,6 @@ struct driver_data {
 	struct sg_table tx_sgt;
 	int rx_nents;
 	int tx_nents;
-	void *dummy;
 	atomic_t dma_running;
 
 	/* Current message transfer state info */