linux-kernel - Re: [PATCH 11/15] tty: msm_serial: use dmaengine_prep_slave

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Date: Fri, 19 Apr 2024 09:53:06 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Marek Szyprowski <m.szyprowski@...sung.com>, gregkh@...uxfoundation.org
Cc: linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konrad.dybcio@...aro.org>, linux-arm-msm@...r.kernel.org,
 Anders Roxell <anders.roxell@...aro.org>
Subject: Re: [PATCH 11/15] tty: msm_serial: use dmaengine_prep_slave_sg()

On 19. 04. 24, 9:43, Jiri Slaby wrote:
> On 17. 04. 24, 14:45, Marek Szyprowski wrote:
>> I alse tried to change the "if (dma->mapped)" check in msm_start_tx() to:
>>
>> 1. if (dma->tx_sg.length)
>>
>> 2. if (dma->tx_sg.page_link & ~SG_PAGE_LINK_MASK)
>>
>> but none of the above worked what is really strange and incomprehensible
>> for me.
>>
> 
> Aaaah, nevermind, what about this?
> 
> Two bugs:
> 1) dma_map_sg() returns the number of mapped entries. Not zero!
> 2) And I forgot to zero tx_sg in case of error.
> 
> --- a/drivers/tty/serial/msm_serial.c
> +++ b/drivers/tty/serial/msm_serial.c
> @@ -506,8 +506,8 @@ static int msm_handle_tx_dma(struct msm_port 
> *msm_port, unsigned int count)
>          kfifo_dma_out_prepare(&tport->xmit_fifo, &dma->tx_sg, 1, count);
> 
>          ret = dma_map_sg(port->dev, &dma->tx_sg, 1, dma->dir);
> -       if (ret)
> -               return ret;
> +       if (!ret)

Still wrong, ret = -EIO missing in here.

> +               goto zero_out;
> 
>          dma->desc = dmaengine_prep_slave_sg(dma->chan, &dma->tx_sg, 1,
>                                                  DMA_MEM_TO_DEV,
> @@ -548,6 +548,7 @@ static int msm_handle_tx_dma(struct msm_port 
> *msm_port, unsigned int count)
>          return 0;
>   unmap:
>          dma_unmap_sg(port->dev, &dma->tx_sg, 1, dma->dir);
> +zero_out:
>          sg_init_table(&dma->tx_sg, 1);
>          return ret;
>   }
> 
> 
> thanks,

-- 
js
suse labs