On Thu, Sep 19, 2024 at 04:58:14PM +0300, Serge Semin wrote:
> The recently submitted fix-commit revealed a problem in the iDMA32
> platform code. Even though the controller supported only a single master
> the dw_dma_acpi_filter() method hard-coded two master interfaces with IDs
> 0 and 1. As a result the sanity check implemented in the commit
> b336268dde75 ("dmaengine: dw: Add peripheral bus width verification") got
> incorrect interface data width and thus prevented the client drivers
> from configuring the DMA-channel with the EINVAL error returned. E.g. the
> next error was printed for the PXA2xx SPI controller driver trying to
> configure the requested channels:
>
> > [ 164.525604] pxa2xx_spi_pci 0000:00:07.1: DMA slave config failed
> > [ 164.536105] pxa2xx_spi_pci 0000:00:07.1: failed to get DMA TX descriptor
> > [ 164.543213] spidev spi-SPT0001:00: SPI transfer failed: -16
>
> The problem would have been spotted much earlier if the iDMA32 controller
> supported more than one master interfaces. But since it supports just a
> single master and the iDMA32-specific code just ignores the master IDs in
> the CTLLO preparation method, the issue has been gone unnoticed so far.
>
> Fix the problem by specifying a single master ID for both memory and
> peripheral devices on the ACPI-based platforms if there is only one master
> available on the controller. Thus the issue noticed for the iDMA32
> controllers will be eliminated and the ACPI-probed DW DMA controllers will
> be configured with the correct master ID by default.
...
> static bool dw_dma_acpi_filter(struct dma_chan *chan, void *param)
> {
> + struct dw_dma *dw = to_dw_dma(chan->device);
> struct acpi_dma_spec *dma_spec = param;
> struct dw_dma_slave slave = {
> .dma_dev = dma_spec->dev,
> .src_id = dma_spec->slave_id,
> .dst_id = dma_spec->slave_id,
> .m_master = 0,
> - .p_master = 1,
I would leave this line as is and it makes more consistent in my opinion with
the below comments which starts with the words "Fallback to...".
> };
>
> + /*
> + * Fallback to using a single interface for both memory and peripheral
> + * device if there is only one master I/F supported (e.g. iDMA32)
> + */
> + if (dw->pdata->nr_masters == 0)
Why '== 0' and not '== 1'? Or '>= 2' if you wish to be on the save side (however,
that '== 0' case is not obvious to me — do we really have that IRL?).
> + slave.p_master = 0;
> + else
> + slave.p_master = 1;
> +
> +
One blank line is enough.
> return dw_dma_filter(chan, &slave);
> }
...
P.S. I'll test it later this or next week, if Ferry wouldn't beat me up to it.
--
With Best Regards,
Andy Shevchenko
