linux-kernel - Re: [PATCH v2 tty-next 1/3] 8250: microchip: pci1xxxx: Add driver for quad-uart support.

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Message-ID: <cc7d8655cb350b45d547abded44ce839cfe00023.camel@microchip.com>
Date:   Wed, 26 Oct 2022 10:54:18 +0000
From:   <Tharunkumar.Pasumarthi@...rochip.com>
To:     <andy.shevchenko@...il.com>, <Kumaravel.Thiagarajan@...rochip.com>
CC:     <linux-serial@...r.kernel.org>, <etremblay@...tech-controls.com>,
        <gregkh@...uxfoundation.org>, <ilpo.jarvinen@...ux.intel.com>,
        <wander@...hat.com>, <u.kleine-koenig@...gutronix.de>,
        <jk@...abs.org>, <macro@...am.me.uk>, <jirislaby@...nel.org>,
        <johan@...nel.org>, <phil.edworthy@...esas.com>,
        <geert+renesas@...der.be>, <linux-kernel@...r.kernel.org>,
        <lukas@...ner.de>, <UNGLinuxDriver@...rochip.com>
Subject: Re: [PATCH v2 tty-next 1/3] 8250: microchip: pci1xxxx: Add driver for
 quad-uart support.

On Mon, 2022-10-03 at 12:22 +0300, Andy Shevchenko wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the
> content is safe
> > +       return 0;
> > +}
> 
> Do you really have cards that are providing IO ports? If not, simplify
> this accordingly.

Device does not have IO ports. I will remove support in code.

> > +       if (num_vectors == 4)
> 
> This check should take care of all possible MSI >= 2, correct?

Hardware supports 2 modes:
1. One irq vector for all the instances
2. nth irq vector for nth instance
Some subsystem ID like PCI_SUBDEVICE_ID_MCHP_PCI1XXXX_4p and
PCI_SUBDEVICE_ID_MCHP_PCI11414 will fail in 2nd mode if all the 4 irq vectors
are not assigned. Therefore, to reduce complexity, software will handle only 1
or 4 irq vectors. 

> > +       for (i = 0; i < nr_ports; i++) {
> > +               if (num_vectors == 4)
> 
> Ditto.

Hardware supports 2 modes:
1. One irq vector for all the instances
2. nth irq vector for nth instance
Some subsystem ID like PCI_SUBDEVICE_ID_MCHP_PCI1XXXX_4p and
PCI_SUBDEVICE_ID_MCHP_PCI11414 will fail in 2nd mode if all the 4 irq vectors
are not assigned. Therefore, to reduce complexity, software will handle only 1
or 4 irq vectors. 

> > +               .flags          = UART_CAP_FIFO,
> > +       },
> 
> Can you assign this in ->setup() or so instead of adding a new port type?

Okay, I will assign in pci1xxxx_setup API.

Thanks Andy for the review. Going forward, I will be addressing the comments (if
any).

Thanks,
Tharun Kumar P