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SubjectRe: [PATCH v3 3/4] spi: mediatek: Add spi bus for Mediatek MT8173
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On Fri, 2015-07-24 at 18:49 +0100, Mark Brown wrote:
> On Thu, Jul 23, 2015 at 05:10:42PM +0800, Leilk Liu wrote:
>
> This basically seems fine but there's a couple of issues that should be
> relatively easy to fix:
>
> > + mdata->cur_transfer = xfer;
> > + mtk_spi_prepare_transfer(master, xfer);
> > + mtk_spi_setup_packet(master, xfer);
> > +
> > + cnt = (xfer->len % 4) ? (xfer->len / 4 + 1) : (xfer->len / 4);
>
> Please write this as an if statement for legibility.
>

OK, I'll fix it.

> > +static bool mtk_spi_can_dma(struct spi_master *master,
> > + struct spi_device *spi,
> > + struct spi_transfer *xfer)
> > +{
> > + struct mtk_spi *mdata = spi_master_get_devdata(master);
> > +
> > + if (xfer->len > MTK_SPI_MAX_FIFO_SIZE)
> > + mdata->use_dma = true;
> > + else
> > + mdata->use_dma = false;
> > +
> > + return mdata->use_dma;
> > +}
>
> This is broken since can_dma() can be called multiple transfers before
> actually doing a transfer (the current implementation loops over all
> transfers in a message before starting the message) - you can't store
> any local data. The transfer_one() function should do another can_dma()
> check to decide if it can DMA, it shouldn't rely on driver global data.
>

OK, I'll fix it.

> > + if (!mdata->use_dma) {
> > + if (trans->rx_buf) {
>
> This should be a variable set when doing the transfer (or perhaps based
> on checking spi->cur_xfer with can_dma()).
>
> > + for (i = 0; i < trans->len; i++) {
> > + if (i % 4 == 0)
> > + reg_val =
> > + readl(mdata->base + SPI_RX_DATA_REG);
> > + *((u8 *)(trans->rx_buf + i)) =
> > + (reg_val >> ((i % 4) * 8)) & 0xff;
>
> This isn't the clearest code ever... a comment would help.
>
OK, I'll fix it.

> > + if (mdata->tx_sgl && (mdata->tx_sgl_len == 0)) {
> > + mdata->tx_sgl = sg_next(mdata->tx_sgl);
> > + if (mdata->tx_sgl) {
> > + trans->tx_dma = sg_dma_address(mdata->tx_sgl);
> > + mdata->tx_sgl_len = sg_dma_len(mdata->tx_sgl);
> > + }
> > + }
>
> There's a *lot* of code in this interrupt handler, and a lot of it looks
> an awful lot like the contents of mtk_spi_dma_transfer() has been
> cut'n'pasted in. The shared code should all be factored out into a
> function called from both places.

OK, I'll fix it.




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