Re: [PATCH] dmaengine: cppi41: Fix issue with musb and ftdi uart

[Vinod Koul <vkoul@kernel.org>]

Hi Tony,

On 22-10-19, 07:55, Tony Lindgren wrote:

Patch subject should reflect the patch changes not the fix. The patch
title here is not telling me anything about the change below. Pls
consider updating the title.

> 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 stable?

> Cc: Bin Liu <b-liu@ti.com>
> Cc: giulio.benetti@benettiengineering.com
> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Cc: Sebastian Reichel <sre@kernel.org>
> Cc: Skvortsov <andrej.skvortzov@gmail.com>
> Reported-by: Yegor Yefremov <yegorslists@googlemail.com>
> Signed-off-by: Tony Lindgren <tony@atomide.com>
> ---
>  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) {
> +		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)
> -- 
> 2.23.0

-- 
~Vinod