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Message-ID: <566019CC.3060005@atmel.com>
Date: Thu, 3 Dec 2015 11:30:36 +0100
From: Nicolas Ferre <nicolas.ferre@...el.com>
To: Ludovic Desroches <ludovic.desroches@...el.com>,
<wsa@...-dreams.de>, <alexandre.belloni@...e-electrons.com>
CC: <linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<plagnioj@...osoft.com>, <linux-arm-kernel@...ts.infradead.org>,
<devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] i2c: at91: add support for the HOLD field
Le 03/12/2015 10:53, Ludovic Desroches a écrit :
> The hold field allows to configure the data hold time which can be set
> with the help of the generic binding 'i2c-sda-hold-time-ns'. This
> feature has been introduced with SAMA5D4 SoC family.
>
> Signed-off-by: Ludovic Desroches <ludovic.desroches@...el.com>
Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>
> ---
> drivers/i2c/busses/i2c-at91.c | 53 ++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 50 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
> index 10835d1..921d32b 100644
> --- a/drivers/i2c/busses/i2c-at91.c
> +++ b/drivers/i2c/busses/i2c-at91.c
> @@ -64,6 +64,8 @@
> #define AT91_TWI_IADR 0x000c /* Internal Address Register */
>
> #define AT91_TWI_CWGR 0x0010 /* Clock Waveform Generator Reg */
> +#define AT91_TWI_CWGR_HOLD_MAX 0x1f
> +#define AT91_TWI_CWGR_HOLD(x) (((x) & AT91_TWI_CWGR_HOLD_MAX) << 24)
>
> #define AT91_TWI_SR 0x0020 /* Status Register */
> #define AT91_TWI_TXCOMP BIT(0) /* Transmission Complete */
> @@ -110,6 +112,7 @@ struct at91_twi_pdata {
> unsigned clk_offset;
> bool has_unre_flag;
> bool has_alt_cmd;
> + bool has_hold_field;
> struct at_dma_slave dma_slave;
> };
>
> @@ -187,10 +190,11 @@ static void at91_init_twi_bus(struct at91_twi_dev *dev)
> */
> static void at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
> {
> - int ckdiv, cdiv, div;
> + int ckdiv, cdiv, div, hold = 0;
> struct at91_twi_pdata *pdata = dev->pdata;
> int offset = pdata->clk_offset;
> int max_ckdiv = pdata->clk_max_div;
> + u32 twd_hold_time_ns = 0;
>
> div = max(0, (int)DIV_ROUND_UP(clk_get_rate(dev->clk),
> 2 * twi_clk) - offset);
> @@ -204,8 +208,33 @@ static void at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
> cdiv = 255;
> }
>
> - dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv;
> - dev_dbg(dev->dev, "cdiv %d ckdiv %d\n", cdiv, ckdiv);
> + if (pdata->has_hold_field) {
> + of_property_read_u32(dev->dev->of_node, "i2c-sda-hold-time-ns",
> + &twd_hold_time_ns);
> +
> + /*
> + * hold time = HOLD + 3 x T_peripheral_clock
> + * Use clk rate in kHz to prevent overflows when computing
> + * hold.
> + */
> + hold = DIV_ROUND_UP(twd_hold_time_ns
> + * (clk_get_rate(dev->clk) / 1000), 1000000);
> + hold -= 3;
> + if (hold < 0)
> + hold = 0;
> + if (hold > AT91_TWI_CWGR_HOLD_MAX) {
> + dev_warn(dev->dev,
> + "HOLD field set to its maximum value (%d instead of %d)\n",
> + AT91_TWI_CWGR_HOLD_MAX, hold);
> + hold = AT91_TWI_CWGR_HOLD_MAX;
> + }
> + }
> +
> + dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv
> + | AT91_TWI_CWGR_HOLD(hold);
> +
> + dev_dbg(dev->dev, "cdiv %d ckdiv %d hold %d (%d ns)\n",
> + cdiv, ckdiv, hold, twd_hold_time_ns);
> }
>
> static void at91_twi_dma_cleanup(struct at91_twi_dev *dev)
> @@ -797,6 +826,7 @@ static struct at91_twi_pdata at91rm9200_config = {
> .clk_offset = 3,
> .has_unre_flag = true,
> .has_alt_cmd = false,
> + .has_hold_field = false,
> };
>
> static struct at91_twi_pdata at91sam9261_config = {
> @@ -804,6 +834,7 @@ static struct at91_twi_pdata at91sam9261_config = {
> .clk_offset = 4,
> .has_unre_flag = false,
> .has_alt_cmd = false,
> + .has_hold_field = false,
> };
>
> static struct at91_twi_pdata at91sam9260_config = {
> @@ -811,6 +842,7 @@ static struct at91_twi_pdata at91sam9260_config = {
> .clk_offset = 4,
> .has_unre_flag = false,
> .has_alt_cmd = false,
> + .has_hold_field = false,
> };
>
> static struct at91_twi_pdata at91sam9g20_config = {
> @@ -818,6 +850,7 @@ static struct at91_twi_pdata at91sam9g20_config = {
> .clk_offset = 4,
> .has_unre_flag = false,
> .has_alt_cmd = false,
> + .has_hold_field = false,
> };
>
> static struct at91_twi_pdata at91sam9g10_config = {
> @@ -825,6 +858,7 @@ static struct at91_twi_pdata at91sam9g10_config = {
> .clk_offset = 4,
> .has_unre_flag = false,
> .has_alt_cmd = false,
> + .has_hold_field = false,
> };
>
> static const struct platform_device_id at91_twi_devtypes[] = {
> @@ -854,6 +888,15 @@ static struct at91_twi_pdata at91sam9x5_config = {
> .clk_offset = 4,
> .has_unre_flag = false,
> .has_alt_cmd = false,
> + .has_hold_field = false,
> +};
> +
> +static struct at91_twi_pdata sama5d4_config = {
> + .clk_max_div = 7,
> + .clk_offset = 4,
> + .has_unre_flag = false,
> + .has_alt_cmd = false,
> + .has_hold_field = true,
> };
>
> static struct at91_twi_pdata sama5d2_config = {
> @@ -861,6 +904,7 @@ static struct at91_twi_pdata sama5d2_config = {
> .clk_offset = 4,
> .has_unre_flag = true,
> .has_alt_cmd = true,
> + .has_hold_field = true,
> };
>
> static const struct of_device_id atmel_twi_dt_ids[] = {
> @@ -883,6 +927,9 @@ static const struct of_device_id atmel_twi_dt_ids[] = {
> .compatible = "atmel,at91sam9x5-i2c",
> .data = &at91sam9x5_config,
> }, {
> + .compatible = "atmel,sama5d4-i2c",
> + .data = &sama5d4_config,
> + }, {
> .compatible = "atmel,sama5d2-i2c",
> .data = &sama5d2_config,
> }, {
>
--
Nicolas Ferre
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