From mboxrd@z Thu Jan  1 00:00:00 1970
From: cyndis@kapsi.fi (Mikko Perttunen)
Date: Sun, 13 May 2018 21:06:37 +0300
Subject: [PATCH 6/8] serial: Add Tegra Combined UART driver
In-Reply-To: <CABb+yY3snB9o4e14by4xui+o_Vhqpe2zh6Pp_e0t-DCTKvMHWA@mail.gmail.com>
References: <20180508114403.14499-1-mperttunen@nvidia.com>
 <20180508114403.14499-7-mperttunen@nvidia.com>
 <CABb+yY3snB9o4e14by4xui+o_Vhqpe2zh6Pp_e0t-DCTKvMHWA@mail.gmail.com>
Message-ID: <4d6aab52-9c99-8dd8-556d-86f32d9f6234@kapsi.fi>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 05/13/2018 06:36 PM, Jassi Brar wrote:
> On Tue, May 8, 2018 at 5:14 PM, Mikko Perttunen <mperttunen@nvidia.com> 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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