On Mon, May 21, 2012 at 4:30 AM, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 21 May 2012 14:19:34 +0800 > "Donald" <donald@xxxxxxxxxxx> wrote: > >> Hi, >> >> This is Donald from ASIX Electronics Corp. My company has three PCI to Serial controllers, including MCS9845, MCS9835, and MCS9820. >> Currently those serial devices using these three chips can directly use the Linux kernel's serial driver in >> linux/drivers/char/8250.c. Recently we find these three chips have a hardware bug relating to parity error count function. We have a >> software workaround for this issue. Below for reference is a pseudo code for this workaround. > > Actually I have a second question. > > Would it not be better to set the device to 8N1 and do the parity in > software rather than lose the FIFO, especially at higher speeds ? Can you > clarify what the erratum is triggered by ? > > Alan I saw your suggestion and thought it could work for a UART we are working with as well, which cannot identify which bytes have parity errors. However, It seems that doing parity in software would be a fine solution if you are using less than 8 data bits, but would not work with 8 bits + parity. Unless the UART supports 9 data bits, you would be unable to read the parity byte from the UART, and would still have the same problem. -Jason From: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> To: "Donald" <donald@xxxxxxxxxxx> Cc: <linux-serial@xxxxxxxxxxxxxxx> Date: 05/21/2012 04:29 AM Subject: Re: Questions regarding adding a patch in linux/drivers/char/8250.c Sent by: linux-serial-owner@xxxxxxxxxxxxxxx On Mon, 21 May 2012 14:19:34 +0800 "Donald" <donald@xxxxxxxxxxx> wrote: > Hi, > > This is Donald from ASIX Electronics Corp. My company has three PCI to Serial controllers, including MCS9845, MCS9835, and MCS9820. > Currently those serial devices using these three chips can directly use the Linux kernel's serial driver in > linux/drivers/char/8250.c. Recently we find these three chips have a hardware bug relating to parity error count function. We have a > software workaround for this issue. Below for reference is a pseudo code for this workaround. Actually I have a second question. Would it not be better to set the device to 8N1 and do the parity in software rather than lose the FIFO, especially at higher speeds ? Can you clarify what the erratum is triggered by ? Alan -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
