spi/tegra114: add spi driver

Hello Laxman Dewangan,

The patch f333a331adfa: "spi/tegra114: add spi driver" from Feb 22, 2013, leads to the following static checker warning:

	drivers/spi/spi-tegra114.c:621 tegra_spi_init_dma_param()
	error: uninitialized variable 'dma_phys'.

drivers/spi/spi-tegra114.c

   583          dma_addr_t dma_phys;
                ^^^^^^^^^^^^^^^^^^^

584 int ret;
585 struct dma_slave_config dma_sconfig;
586
587 dma_chan = dma_request_slave_channel_reason(tspi->dev,
588 dma_to_memory ? "rx" : "tx");
589 if (IS_ERR(dma_chan)) {
590 ret = PTR_ERR(dma_chan);
591 if (ret != -EPROBE_DEFER)
592 dev_err(tspi->dev,
593 "Dma channel is not available: %d\n", ret);
594 return ret;
595 }
596
597 dma_buf = dma_alloc_coherent(tspi->dev, tspi->dma_buf_size,
598 &dma_phys, GFP_KERNEL);

The issue is that in dma_alloc_attrs() if we can dma_alloc_from_coherent() then dma_phys is not set. I'm getting a couple similar errors and I'm not certian what to do about it.

599 if (!dma_buf) {

   600                  dev_err(tspi->dev, " Not able to allocate the dma buffer\n");
   601                  dma_release_channel(dma_chan);
   602                  return -ENOMEM;
   603          }
   604  
   605          if (dma_to_memory) {
   606                  dma_sconfig.src_addr = tspi->phys + SPI_RX_FIFO;
   607                  dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
   608                  dma_sconfig.src_maxburst = 0;
   609          } else {
   610                  dma_sconfig.dst_addr = tspi->phys + SPI_TX_FIFO;
   611                  dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
   612                  dma_sconfig.dst_maxburst = 0;
   613          }
   614  
   615          ret = dmaengine_slave_config(dma_chan, &dma_sconfig);
   616          if (ret)
   617                  goto scrub;
   618          if (dma_to_memory) {
   619                  tspi->rx_dma_chan = dma_chan;
   620                  tspi->rx_dma_buf = dma_buf;
   621                  tspi->rx_dma_phys = dma_phys;
                                            ^^^^^^^^

Uninitialized.

   622          } else {
   623                  tspi->tx_dma_chan = dma_chan;
   624                  tspi->tx_dma_buf = dma_buf;
   625                  tspi->tx_dma_phys = dma_phys;

regards,
dan carpenter
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The issue is with compiler actually.
we have code as

        dma_buf = dma_alloc_coherent(tspi->dev, tspi->dma_buf_size,
                                &dma_phys, GFP_KERNEL);
        if (!dma_buf) {
                dev_err(tspi->dev, " Not able to allocate the dma 
buffer\n");
                dma_release_channel(dma_chan);
                return -ENOMEM;
        }

So if returned value "dma_buf" is not NULL then we can assume that dma_phy is initialized other wise it should return NULL.

The static check is not able to find out that calling function has initialized it or not.

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Oh... Duh. I read this code but I got my variables switched around in my head. The static checker finds the code confusing in a different way than I did...

Thanks for taking a look.

regards,
dan carpenter