Hello!
On 10/23/2019 06:31 PM, Tony Lindgren wrote:
> Yegor Yefremov <yegorsli...@googlemail.com> reported that musb and ftdi
> uart can fail for the first open of the uart unless connected using
> a hub.
>
> This is because the first dma call done by musb_ep_program() must wait
> if cppi41 is PM runtime suspended. Otherwise musb_ep_program() continues
> with other non-dma packets before the DMA transfer is started causing at
> least ftdi uarts to fail to receive data.
>
> Let's fix the issue by waking up cppi41 with PM runtime calls added to
> cppi41_dma_prep_slave_sg() and return NULL if still idled. This way we
> have musb_ep_program() continue with PIO until cppi41 is awake.
>
> Fixes: fdea2d09b997 ("dmaengine: cppi41: Add basic PM runtime support")
> Cc: Bin Liu <b-...@ti.com>
> Cc: giulio.bene...@benettiengineering.com
> Cc: Sebastian Andrzej Siewior <bige...@linutronix.de>
> Cc: Sebastian Reichel <s...@kernel.org>
> Cc: Skvortsov <andrej.skvort...@gmail.com>
> Reported-by: Yegor Yefremov <yegorsli...@googlemail.com>
> Signed-off-by: Tony Lindgren <t...@atomide.com>
> ---
>
> Please consider adding Cc stable v4.9+ tag when committing
>
> ---
> drivers/dma/ti/cppi41.c | 21 ++++++++++++++++++++-
> 1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/ti/cppi41.c b/drivers/dma/ti/cppi41.c
> --- a/drivers/dma/ti/cppi41.c
> +++ b/drivers/dma/ti/cppi41.c
> @@ -586,9 +586,22 @@ static struct dma_async_tx_descriptor
> *cppi41_dma_prep_slave_sg(
> enum dma_transfer_direction dir, unsigned long tx_flags, void *context)
> {
> struct cppi41_channel *c = to_cpp41_chan(chan);
> + struct dma_async_tx_descriptor *txd = NULL;
> + struct cppi41_dd *cdd = c->cdd;
> struct cppi41_desc *d;
> struct scatterlist *sg;
> unsigned int i;
> + int error;
> +
> + error = pm_runtime_get(cdd->ddev.dev);
> + if (error < 0) {
I'd call that variable 'status', comparison (error < 0) just doesn't look
right.
If it was *if* (error), it would have been more correct.
> + pm_runtime_put_noidle(cdd->ddev.dev);
> +
> + return NULL;
> + }
> +
> + if (cdd->is_suspended)
> + goto err_out_not_ready;
>
> d = c->desc;
> for_each_sg(sgl, sg, sg_len, i) {
[...]
MBR, Sergei
