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

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Date: Tue, 16 Apr 2024 12:23:12 +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
Subject: Re: [PATCH 11/15] tty: msm_serial: use dmaengine_prep_slave_sg()

On 15. 04. 24, 23:17, Marek Szyprowski wrote:
> On 05.04.2024 08:08, Jiri Slaby (SUSE) wrote:
>> This is a preparatory for the serial-to-kfifo switch. kfifo understands
>> only scatter-gatter approach, so switch to that.
>>
>> No functional change intended, it's just dmaengine_prep_slave_single()
>> inline expanded.
>>
>> And in this case, switch from dma_map_single() to dma_map_sg() too. This
>> needs struct msm_dma changes. I split the rx and tx parts into an union.
>> TX is now struct scatterlist, RX remains the old good phys-virt-count
>> triple.
>>
>> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
>> Cc: Bjorn Andersson <andersson@...nel.org>
>> Cc: Konrad Dybcio <konrad.dybcio@...aro.org>
>> Cc: linux-arm-msm@...r.kernel.org
> 
> I've just found that this patch broke UART operation on DragonBoard
> 410c. I briefly checked and didn't notice anything obviously wrong here,
> but the board stops transmitting any data from its serial port after the
> first message. I will try to analyze this issue a bit more tomorrow.

I double checked, but I see no immediate issues in the patch too. So 
please, if you can analyze this more…

thanks,
-- 
js
suse labs