> On 26/10/2022 05:44, Akhil R wrote:
> >> On Thu, Oct 20, 2022 at 02:03:22PM +0530, Akhil R wrote:
> >>> Add support for dma-channel-mask so that only the specified channels
> >>> are used. This helps to reserve some channels for the firmware.
> >>>
> >>> This was initially achieved by limiting the channel number to 31 in
> >>> the driver and adjusting the register address to skip channel0 which
> >>> was reserved for a firmware. Now, with this change, the driver can
> >>> align more to the actual hardware which has 32 channels.
> >>>
> >>> Signed-off-by: Akhil R <akhilrajeev@xxxxxxxxxx>
> >>> Reviewed-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> >>> ---
> >>> drivers/dma/tegra186-gpc-dma.c | 37 +++++++++++++++++++++++++++----
> ---
> >>> 1 file changed, 30 insertions(+), 7 deletions(-)
> >>>
> >>> diff --git a/drivers/dma/tegra186-gpc-dma.c b/drivers/dma/tegra186-gpc-
> >> dma.c
> >>> index fa9bda4a2bc6..1d1180db6d4e 100644
> >>> --- a/drivers/dma/tegra186-gpc-dma.c
> >>> +++ b/drivers/dma/tegra186-gpc-dma.c
> >>> @@ -161,7 +161,10 @@
> >>> #define TEGRA_GPCDMA_BURST_COMPLETION_TIMEOUT 5000 /* 5
> >> msec */
> >>>
> >>> /* Channel base address offset from GPCDMA base address */
> >>> -#define TEGRA_GPCDMA_CHANNEL_BASE_ADD_OFFSET 0x20000
> >>> +#define TEGRA_GPCDMA_CHANNEL_BASE_ADDR_OFFSET 0x10000
> >>> +
> >>> +/* Default channel mask reserving channel0 */
> >>> +#define TEGRA_GPCDMA_DEFAULT_CHANNEL_MASK 0xfffffffe
> >>>
> >>> struct tegra_dma;
> >>> struct tegra_dma_channel;
> >>> @@ -246,6 +249,7 @@ struct tegra_dma {
> >>> const struct tegra_dma_chip_data *chip_data;
> >>> unsigned long sid_m2d_reserved;
> >>> unsigned long sid_d2m_reserved;
> >>> + u32 chan_mask;
> >>> void __iomem *base_addr;
> >>> struct device *dev;
> >>> struct dma_device dma_dev;
> >>> @@ -1288,7 +1292,7 @@ static struct dma_chan
> *tegra_dma_of_xlate(struct
> >> of_phandle_args *dma_spec,
> >>> }
> >>>
> >>> static const struct tegra_dma_chip_data tegra186_dma_chip_data = {
> >>> - .nr_channels = 31,
> >>> + .nr_channels = 32,
> >>
> >> This is an ABI break. A new kernel with an old DTB will use 32 channels
> >> instead of 31. You should leave this and use the dma-channel-mask to
> >> enable all 32 channels.
> >>
> > Hi Rob,
> >
> > If using an old DTB, tdma->chan_mask will be default to 0xfffffffe since it
> > would not have the dma-channel-mask property. The driver would still
> > use 31 channels even if it uses an old DTB. Shouldn't it prevent the
> > ABI break?
>
> Unfortunately no. Yes for an old DTB without the dma-channel-mask
> property, we set the channel mask to 0xfffffffe, but this is not correct
> because it only has 31 interrupts/channels and not 32. So I think we
> will need to use of_irq_count() here.
>
Shall I put it in a way that only the used interrupts are mentioned in the DT?
With this I can revert the interrupt change in the DT and would not break
the ABI as well.
The code would look something like this.
int chan_count = 0;
if (of_irq_count(pdev->dev.of_node) != hweight_long(tdma->chan_mask)) {
dev_err(&pdev->dev, "Interrupt count doesn't match with channels\n");
return -EINVAL;
}
for (i = 0; i < cdata->nr_channels; i++) {
struct tegra_dma_channel *tdc = &tdma->channels[i];
/* Check for channel mask */
if (!(tdma->chan_mask & BIT(i)))
continue;
tdc->irq = platform_get_irq(pdev, chan_count);
chan_count++;
if (tdc->irq < 0)
return tdc->irq;
...
...
}
Regards,
Akhil
