linux-kernel - Re: [PATCH 5/8] serial: imx: save and restore context in the suspend path

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Message-ID: <CAOMZO5D18DCBXYLA8Z36ZY3wezzS9Nh64d0KWZ==zcFMHaBpsA@mail.gmail.com>
Date:	Mon, 10 Aug 2015 00:30:18 -0300
From:	Fabio Estevam <festevam@...il.com>
To:	Eduardo Valentin <edubezval@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>,
	Linux PM <linux-pm@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Shenwei Wang <shenwei.wang@...escale.com>
Subject: Re: [PATCH 5/8] serial: imx: save and restore context in the suspend path

Hi Eduardo,

On Sun, Aug 9, 2015 at 3:19 PM, Eduardo Valentin <edubezval@...il.com> wrote:
> This change teaches the imx serial driver to save its
> context and restore it across suspend and resume path.
> To do so, it introduces serial_imx_restore_context()
> and serial_imx_save_context() functions. They use
> a shadow set of registers to save key registers
> and restore them accordingly. These functions can
> be reused on other situations, when the device
> context is lost.
>
> Cc: Fabio Stevam <festevam@...il.com>

s/Stevam/Estevam (applies to all the patches)

> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Jiri Slaby <jslaby@...e.com>
> Cc: linux-serial@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Eduardo Valentin <edubezval@...il.com>
> ---
>  drivers/tty/serial/imx.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index a03855d..494b182 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -217,6 +217,8 @@ struct imx_port {
>         unsigned int            tx_bytes;
>         unsigned int            dma_tx_nents;
>         wait_queue_head_t       dma_wait;
> +       unsigned int            saved_reg[8];
> +       bool                    context_saved;
>  };
>
>  struct imx_port_ucrs {
> @@ -1803,6 +1805,36 @@ static struct uart_driver imx_reg = {
>         .cons           = IMX_CONSOLE,
>  };
>
> +static void serial_imx_restore_context(struct imx_port *sport)
> +{
> +       if (!sport->context_saved)
> +               return;
> +
> +       writel(sport->saved_reg[4], sport->port.membase + UFCR);
> +       writel(sport->saved_reg[5], sport->port.membase + UBIR);
> +       writel(sport->saved_reg[6], sport->port.membase + UBMR);
> +       writel(sport->saved_reg[7], sport->port.membase + IMX21_UTS);
> +       writel(sport->saved_reg[0], sport->port.membase + UCR1);
> +       writel(sport->saved_reg[1] | 0x1, sport->port.membase + UCR2);
> +       writel(sport->saved_reg[2], sport->port.membase + UCR3);
> +       writel(sport->saved_reg[3], sport->port.membase + UCR4);
> +       sport->context_saved = false;
> +}
> +
> +static void serial_imx_save_context(struct imx_port *sport)
> +{
> +       /* Save necessary regs */
> +       sport->saved_reg[0] = readl(sport->port.membase + UCR1);
> +       sport->saved_reg[1] = readl(sport->port.membase + UCR2);
> +       sport->saved_reg[2] = readl(sport->port.membase + UCR3);
> +       sport->saved_reg[3] = readl(sport->port.membase + UCR4);
> +       sport->saved_reg[4] = readl(sport->port.membase + UFCR);
> +       sport->saved_reg[5] = readl(sport->port.membase + UBIR);
> +       sport->saved_reg[6] = readl(sport->port.membase + UBMR);
> +       sport->saved_reg[7] = readl(sport->port.membase + IMX21_UTS);
> +       sport->context_saved = true;
> +}

This seems to be similar to what Shenwei posted earlier:
http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/360841.html

Regards,

Fabio Estevam
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