linux-kernel - Re: [PATCH] serial: 8250_omap: Implementation of Errata i2310

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Date: Fri, 14 Jun 2024 15:08:11 +0530
From: "Kumar, Udit" <u-kumar1@...com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
CC: <vigneshr@...com>, <nm@...com>, Tony Lindgren <tony@...mide.com>,
        Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby
	<jirislaby@...nel.org>, <ronald.wahl@...itan.com>,
        <thomas.richard@...tlin.com>, <tglx@...utronix.de>,
        LKML
	<linux-kernel@...r.kernel.org>,
        linux-serial <linux-serial@...r.kernel.org>
Subject: Re: [PATCH] serial: 8250_omap: Implementation of Errata i2310


On 6/14/2024 1:58 PM, Ilpo Järvinen wrote:
> On Fri, 14 Jun 2024, Udit Kumar wrote:
>
>> As per Errata i2310[0], Erroneous timeout can be triggered,
>> if this Erroneous interrupt is not cleared then it may leads
>> to strom of interrupts, therefore apply Errata i2310 solution.
>>
>> [0] https://www.ti.com/lit/pdf/sprz536 page 23
>>
>> Signed-off-by: Udit Kumar <u-kumar1@...com>
>> ---
>>   drivers/tty/serial/8250/8250_omap.c | 25 ++++++++++++++++++++-----
>>   1 file changed, 20 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
>> index 170639d12b2a..38eb639f78d3 100644
>> --- a/drivers/tty/serial/8250/8250_omap.c
>> +++ b/drivers/tty/serial/8250/8250_omap.c
>> @@ -115,6 +115,10 @@
>>   /* RX FIFO occupancy indicator */
>>   #define UART_OMAP_RX_LVL		0x19
>>   
>> +/* Timeout Low and High */
>> +#define UART_OMAP_TO_L                 0x26
>> +#define UART_OMAP_TO_H                 0x27
>> +
>>   /*
>>    * Copy of the genpd flags for the console.
>>    * Only used if console suspend is disabled
>> @@ -663,13 +667,24 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
>>   
>>   	/*
>>   	 * On K3 SoCs, it is observed that RX TIMEOUT is signalled after
>> -	 * FIFO has been drained, in which case a dummy read of RX FIFO
>> -	 * is required to clear RX TIMEOUT condition.
>> +	 * FIFO has been drained or erroneously.
>> +	 * So apply solution of Errata i2310 as mentioned in
>> +	 * https://www.ti.com/lit/pdf/sprz536
>>   	 */
>>   	if (priv->habit & UART_RX_TIMEOUT_QUIRK &&
>> -	    (iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT &&
>> -	    serial_port_in(port, UART_OMAP_RX_LVL) == 0) {
>> -		serial_port_in(port, UART_RX);
>> +		(iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT) {
>> +		unsigned char efr2, timeout_h, timeout_l;
>> +
>> +		efr2 = serial_in(up, UART_OMAP_EFR2);
>> +		timeout_h = serial_in(up, UART_OMAP_TO_H);
>> +		timeout_l = serial_in(up, UART_OMAP_TO_L);
>> +		serial_out(up, UART_OMAP_TO_H, 0xFF);
>> +		serial_out(up, UART_OMAP_TO_L, 0xFF);
>> +		serial_out(up, UART_OMAP_EFR2, 0x1);
> Eh, this doesn't match the workaround in the errata???
>
> Also, don't use literals but name the bits with defines (for the correct
> bit there's probably a pre-existing define but it's not named as good as
> it could be, I'd say it should be named as
> UART_OMAP_EFR2_TIMEOUT_PERIODIC).


Thanks, will address in v2.


>
>> +		serial_in(up, UART_IIR);
>> +		serial_out(up, UART_OMAP_EFR2, efr2);
>> +		serial_out(up, UART_OMAP_TO_H, timeout_h);
>> +		serial_out(up, UART_OMAP_TO_L, timeout_l);