Hi Tony,
On 10/23/19 6:31 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 pm_runtime_get()
pm_runtime_mark_last_busy()+pm_runtime_put_autosuspend() around a code
which updates a descriptor in _memory_ helps then this best described as
works by luck ;)
I have a feeling that if you put enough delay between prepare_sg and
issue_pending in the usb driver then it will keep failing, no?
fwiw, in the cppi41_dma_issue_pending() the driver does:
error = pm_runtime_get(cdd->ddev.dev);
...
if (!cdd->is_suspended)
cppi41_run_queue(cdd);
...
pm_runtime_mark_last_busy(cdd->ddev.dev);
pm_runtime_put_autosuspend(cdd->ddev.dev);
Without waiting for the transfer to complete?
If issue_pending is not starting the transfer right away then the whole
pm handling is broken in there. imho.
runtime_get in prep_slave_sg and runtime_put when the transfer is finished?
> + if (error < 0) {
> + 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) {
> @@ -611,7 +624,13 @@ static struct dma_async_tx_descriptor
> *cppi41_dma_prep_slave_sg(
> d++;
> }
>
> - return &c->txd;
> + txd = &c->txd;
> +
> +err_out_not_ready:
> + pm_runtime_mark_last_busy(cdd->ddev.dev);
> + pm_runtime_put_autosuspend(cdd->ddev.dev);
> +
> + return txd;
> }
>
> static void cppi41_compute_td_desc(struct cppi41_desc *d)
>
- Peter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
