Re: [PATCH 11/15] tty: msm_serial: use dmaengine_prep_slave_sg()

From: Jiri Slaby
Date: Fri Apr 19 2024 - 04:09:25 EST


On 19. 04. 24, 10:00, Marek Szyprowski wrote:
On 19.04.2024 09:53, Jiri Slaby wrote:
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.

"if (ret <= 0)" seems to be better here.

It returns unsigned, so I have a better patch. Will send in a second.

Indeed this fixed the issue. I checked the code many times, but I missed
this dma_map_sg() return value issue.

Perfect!

Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

Could you test that one too :)?

thanks,
--
js
suse labs