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* cpm_uart non-console problem with write on 2nd open..
@ 2006-09-14 13:30 Alexandros Kostopoulos
  2006-09-14 13:37 ` Vitaly Bordug
  0 siblings, 1 reply; 2+ messages in thread
From: Alexandros Kostopoulos @ 2006-09-14 13:30 UTC (permalink / raw)
  To: linuxppc-dev

I'm experiencing a problem with the 2.6.13 cpm_uart driver. When opening=
  =

the device for the second time after the driver was inserted, if only a =
 =

few bytes are sent for transmission and the device is then closed, the  =

tx_empty routine called by shutdown returns 0 and the latter hangs in th=
e  =

while loop with the call to cpm_uart_tx_empty. No bytes are actually  =

transmitted from the uart.

I found out that the difference between the first and subsequent open  =

calls is that during the first time (and until the first shutdown) the  =

transmitter is enabled in GSMRL. From this point on, the transmitter is =
 =

initially disabled on startup. Thus, if only a few bytes are queued for =
 =

transmission before shutdown and a TX interrupt is not triggered, the  =

bytes are never sent, and thus the shutdown function hangs on the  =

cpm_uart_tx_empty loop.

The fix that works for me is the following:

Index: drivers/serial/cpm_uart/cpm_uart_core.c
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- drivers/serial/cpm_uart/cpm_uart_core.c     (revision 106)
+++ drivers/serial/cpm_uart/cpm_uart_core.c     (working copy)

@@ -394,7 +394,7 @@ static int cpm_uart_startup(struct uart_
                 pinfo->smcp->smc_smcmr |=3D SMCMR_REN;
         } else {
                 pinfo->sccp->scc_sccm |=3D UART_SCCM_RX;
-        pinfo->sccp->scc_gsmrl |=3D (SCC_GSMRL_ENR);
+        pinfo->sccp->scc_gsmrl |=3D (SCC_GSMRL_ENR | SCC_GSMRL_ENT);

         }

Any comments would be greatly appreciated

thank you

Alex

^ permalink raw reply	[flat|nested] 2+ messages in thread

• * Re: cpm_uart non-console problem with write on 2nd open..
    2006-09-14 13:30 cpm_uart non-console problem with write on 2nd open Alexandros Kostopoulos
  @ 2006-09-14 13:37 ` Vitaly Bordug
    0 siblings, 0 replies; 2+ messages in thread
  From: Vitaly Bordug @ 2006-09-14 13:37 UTC (permalink / raw)
    To: Alexandros Kostopoulos; +Cc: linuxppc-dev
  
  On Thu, 14 Sep 2006 16:30:44 +0300
  "Alexandros Kostopoulos" <akostop@inaccessnetworks•com> wrote:
  
  > I'm experiencing a problem with the 2.6.13 cpm_uart driver. When opening  
  > the device for the second time after the driver was inserted, if only a  
  > few bytes are sent for transmission and the device is then closed, the  
  > tx_empty routine called by shutdown returns 0 and the latter hangs in the  
  > while loop with the call to cpm_uart_tx_empty. No bytes are actually  
  > transmitted from the uart.
  > 
  It was addressed a while ago, fix should be in the latest stable kernel rev. for certain.
  
  The snippet below was not the only thing to get problem completely resolved; 
  You may glance at the code within current kernel, if still experiencing problems.
  
  Thanks, Vitaly
  
  > I found out that the difference between the first and subsequent open  
  > calls is that during the first time (and until the first shutdown) the  
  > transmitter is enabled in GSMRL. From this point on, the transmitter is  
  > initially disabled on startup. Thus, if only a few bytes are queued for  
  > transmission before shutdown and a TX interrupt is not triggered, the  
  > bytes are never sent, and thus the shutdown function hangs on the  
  > cpm_uart_tx_empty loop.
  > 
  > The fix that works for me is the following:
  > 
  > Index: drivers/serial/cpm_uart/cpm_uart_core.c
  > ===================================================================
  > --- drivers/serial/cpm_uart/cpm_uart_core.c     (revision 106)
  > +++ drivers/serial/cpm_uart/cpm_uart_core.c     (working copy)
  > 
  > @@ -394,7 +394,7 @@ static int cpm_uart_startup(struct uart_
  >                  pinfo->smcp->smc_smcmr |= SMCMR_REN;
  >          } else {
  >                  pinfo->sccp->scc_sccm |= UART_SCCM_RX;
  > -        pinfo->sccp->scc_gsmrl |= (SCC_GSMRL_ENR);
  > +        pinfo->sccp->scc_gsmrl |= (SCC_GSMRL_ENR | SCC_GSMRL_ENT);
  > 
  >          }
  > 
  > Any comments would be greatly appreciated
  > 
  > thank you
  > 
  > Alex
  > _______________________________________________
  > Linuxppc-dev mailing list
  > Linuxppc-dev@ozlabs•org
  > https://ozlabs.org/mailman/listinfo/linuxppc-dev
  > 
  > 
  
  
  -- 
  Sincerely, 
  Vitaly
  
  ^ permalink raw reply	[flat|nested] 2+ messages in thread

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