Messages in this thread Patch in this message |  | | Date | Wed, 16 May 2001 16:12:45 -0600 | From | Val Henson <> | Subject | Re: [PATCH] drivers/char/serial.c bug in ST16C654 detection |
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Anyone know where Ted Tso is? He hasn't posted in several weeks. Alan, will you put this in -ac? This patch fixes a bug in serial.c that causes a crash on machines with a ST16C654.
On Tue, May 15, 2001 at 09:52:01AM -0400, Stuart MacDonald wrote:
> Kernel version? Distribution? Are you using a serial console?
2.4.5-pre1 (see patch).
> The revision should always be saved if it's available. Hmm. > I didn't look carefully yesterday. The DLL always contains the > revision for the 85x family. Why do you think it doesn't?
Because the comment was ambiguous. I don't have the data sheet for the 85x family so I just wrote the code according to the comment. I'll change the comment to make it clear.
> I think your patch below is good, I'm just mystified by this > kablooey thing.
Thanks. Corrected version of the patch is below.
-VAL
--- linux-2.4.5-pre1/drivers/char/serial.c Thu Apr 19 00:26:34 2001 +++ linux/drivers/char/serial.c Thu May 17 03:12:09 2001 @@ -3507,7 +3507,7 @@ struct serial_state *state, unsigned long flags) { - unsigned char scratch, scratch2, scratch3; + unsigned char scratch, scratch2, scratch3, scratch4; /* * First we check to see if it's an Oxford Semiconductor UART. @@ -3548,20 +3548,33 @@ * then reading back DLL and DLM. If DLM reads back 0x10, * then the UART is a XR16C850 and the DLL contains the chip * revision. If DLM reads back 0x14, then the UART is a - * XR16C854. - * + * XR16C854 and the DLL contains the chip revision. */ + + /* Save the DLL and DLM */ + serial_outp(info, UART_LCR, UART_LCR_DLAB); + scratch3 = serial_inp(info, UART_DLL); + scratch4 = serial_inp(info, UART_DLM); + serial_outp(info, UART_DLL, 0); serial_outp(info, UART_DLM, 0); - state->revision = serial_inp(info, UART_DLL); + scratch2 = serial_inp(info, UART_DLL); scratch = serial_inp(info, UART_DLM); serial_outp(info, UART_LCR, 0); + if (scratch == 0x10 || scratch == 0x14) { + state->revision = scratch2; state->type = PORT_16850; return; } + /* Restore the DLL and DLM */ + + serial_outp(info, UART_LCR, UART_LCR_DLAB); + serial_outp(info, UART_DLL, scratch3); + serial_outp(info, UART_DLM, scratch4); + serial_outp(info, UART_LCR, 0); /* * We distinguish between the '654 and the '650 by counting * how many bytes are in the FIFO. I'm using this for now,
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