linux-kernel - RE: [PATCH 10/14] serial: tegra: add support to use 8 bytes trigger

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Date:   Tue, 27 Aug 2019 09:31:00 +0000
From:   Krishna Yarlagadda <kyarlagadda@...dia.com>
To:     Jonathan Hunter <jonathanh@...dia.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        "jslaby@...e.com" <jslaby@...e.com>
CC:     "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Shardar Mohammed" <smohammed@...dia.com>
Subject: RE: [PATCH 10/14] serial: tegra: add support to use 8 bytes trigger

> -----Original Message-----
> From: Jonathan Hunter <jonathanh@...dia.com>
> Sent: Tuesday, August 20, 2019 1:59 AM
> To: Krishna Yarlagadda <kyarlagadda@...dia.com>;
> gregkh@...uxfoundation.org; robh+dt@...nel.org; mark.rutland@....com;
> thierry.reding@...il.com; Laxman Dewangan <ldewangan@...dia.com>;
> jslaby@...e.com
> Cc: linux-serial@...r.kernel.org; devicetree@...r.kernel.org; linux-
> tegra@...r.kernel.org; linux-kernel@...r.kernel.org; Shardar Mohammed
> <smohammed@...dia.com>
> Subject: Re: [PATCH 10/14] serial: tegra: add support to use 8 bytes trigger
> 
> 
> On 12/08/2019 12:28, Krishna Yarlagadda wrote:
> > From: Shardar Shariff Md <smohammed@...dia.com>
> >
> > Add support to use 8 bytes trigger for Tegra186 SOC.
> >
> > Signed-off-by: Shardar Shariff Md <smohammed@...dia.com>
> > Signed-off-by: Krishna Yarlagadda <kyarlagadda@...dia.com>
> > ---
> >  drivers/tty/serial/serial-tegra.c | 13 +++++++++++--
> >  1 file changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
> > index 329923c..03d1d20 100644
> > --- a/drivers/tty/serial/serial-tegra.c
> > +++ b/drivers/tty/serial/serial-tegra.c
> > @@ -88,6 +88,7 @@ struct tegra_uart_chip_data {
> >  	bool	support_clk_src_div;
> >  	bool	fifo_mode_enable_status;
> >  	int	uart_max_port;
> > +	int	dma_burst_bytes;
> 
> I assume that this is a maximum, so why not say max_dma_burst_bytes?
Yes. This is maximum. Will update.

> 
> >  };
> >
> >  struct tegra_uart_port {
> > @@ -933,7 +934,12 @@ static int tegra_uart_hw_init(struct
> tegra_uart_port *tup)
> >  	 * programmed in the DMA registers.
> >  	 */
> >  	tup->fcr_shadow = UART_FCR_ENABLE_FIFO;
> > -	tup->fcr_shadow |= UART_FCR_R_TRIG_01;
> > +
> > +	if (tup->cdata->dma_burst_bytes == 8)
> > +		tup->fcr_shadow |= UART_FCR_R_TRIG_10;
> > +	else
> > +		tup->fcr_shadow |= UART_FCR_R_TRIG_01;
> > +
> >  	tup->fcr_shadow |= TEGRA_UART_TX_TRIG_16B;
> >  	tegra_uart_write(tup, tup->fcr_shadow, UART_FCR);
> >
> > @@ -1046,7 +1052,7 @@ static int
> tegra_uart_dma_channel_allocate(struct tegra_uart_port *tup,
> >  		}
> >  		dma_sconfig.src_addr = tup->uport.mapbase;
> >  		dma_sconfig.src_addr_width =
> DMA_SLAVE_BUSWIDTH_1_BYTE;
> > -		dma_sconfig.src_maxburst = 4;
> > +		dma_sconfig.src_maxburst = tup->cdata->dma_burst_bytes;
> >  		tup->rx_dma_chan = dma_chan;
> >  		tup->rx_dma_buf_virt = dma_buf;
> >  		tup->rx_dma_buf_phys = dma_phys;
> > @@ -1325,6 +1331,7 @@ static struct tegra_uart_chip_data
> tegra20_uart_chip_data = {
> >  	.support_clk_src_div		= false,
> >  	.fifo_mode_enable_status	= false,
> >  	.uart_max_port			= 5,
> > +	.dma_burst_bytes		= 4,
> 
> Isn't it simpler to store the TRIG value here?
> 
> Jon
TRIG value will have to be converted to max burst and one of it needs to be
derived from other.
KY
> 
> --
> nvpublic