Re: [PATCH 6/8] serial: Add Tegra Combined UART driver

[Mikko Perttunen]

On 05/13/2018 06:36 PM, Jassi Brar wrote:
> On Tue, May 8, 2018 at 5:14 PM, Mikko Perttunen <mperttunen@xxxxxxxxxx> wrote:
>
> ....
> > +config SERIAL_TEGRA_TCU
> > +       tristate "NVIDIA Tegra Combined UART"
> > +       depends on ARCH_TEGRA && MAILBOX
> > +       select SERIAL_CORE
> > +       help
> > +         Support for the mailbox-based TCU (Tegra Combined UART) serial port.
> > +         TCU is a virtual serial port that allows multiplexing multiple data
> > +         streams into a single hardware serial port.
> > +
> Maybe make it depend upon TEGRA_HSP_MBOX ?

Yeah, that probably makes more sense. MAILBOX is enough to build it but 
it won't be of any use without TEGRA_HSP_MBOX.

> ......
>
> > +
> > +static void tegra_tcu_write(const char *s, unsigned int count)
> > +{
> > +       struct tegra_tcu *tcu = tegra_tcu_uart_port.private_data;
> > +       unsigned int written = 0, i = 0;
> > +       bool insert_nl = false;
> > +       uint32_t value = 0;
> > +
> > +       while (i < count) {
> > +               if (insert_nl) {
> > +                       value |= '\n' << (written++ * 8);
> > +                       insert_nl = false;
> > +                       i++;
> > +               } else if (s[i] == '\n') {
> > +                       value |= '\r' << (written++ * 8);
> > +                       insert_nl = true;
> > +               } else {
> > +                       value |= s[i++] << (written++ * 8);
> > +               }
> > +
> > +               if (written == 3) {
> > +                       value |= 3 << 24;
> > +                       value |= BIT(26);
> > +                       mbox_send_message(tcu->tx, &value);
> How is this supposed to work? tegra_hsp_doorbell_send_data() ignores
> the second argument.

The previous patch in the series adds support for what are called 
"shared mailboxes" to the tegra-hsp driver. For these the second 
argument is used.

Thanks,
Mikko

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