From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolas Ferre Subject: Re: [PATCH 1/4] i2c: at91: add upport for the HOLD field Date: Wed, 2 Dec 2015 12:01:49 +0100 Message-ID: <565ECF9D.30707@atmel.com> References: <1449052747-20991-1-git-send-email-ludovic.desroches@atmel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from eusmtp01.atmel.com ([212.144.249.242]:40751 "EHLO eusmtp01.atmel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753553AbbLBLBc (ORCPT ); Wed, 2 Dec 2015 06:01:32 -0500 In-Reply-To: <1449052747-20991-1-git-send-email-ludovic.desroches@atmel.com> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Ludovic Desroches , wsa@the-dreams.de, alexandre.belloni@free-electrons.com Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, plagnioj@jcrosoft.com, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org Le 02/12/2015 11:39, Ludovic Desroches a =E9crit : > The hold field allows to configure the data hold time which can be se= t > with the help of the generic binding 'i2c-sda-hold-time-ns'. This > feature has been introduced with SAMA5D4 SoC family. >=20 > Signed-off-by: Ludovic Desroches > --- > drivers/i2c/busses/i2c-at91.c | 54 +++++++++++++++++++++++++++++++++= +++++++--- > 1 file changed, 51 insertions(+), 3 deletions(-) >=20 > diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-a= t91.c > index 10835d1..09e1690 100644 > --- a/drivers/i2c/busses/i2c-at91.c > +++ b/drivers/i2c/busses/i2c-at91.c > @@ -64,6 +64,7 @@ > #define AT91_TWI_IADR 0x000c /* Internal Address Register */ > =20 > #define AT91_TWI_CWGR 0x0010 /* Clock Waveform Generator Reg */ > +#define AT91_TWI_CWGR_HOLD(x) (((x) & 0x1f) << 24) I would have defined MAX_HOLD here and used it in the mask above... > =20 > #define AT91_TWI_SR 0x0020 /* Status Register */ > #define AT91_TWI_TXCOMP BIT(0) /* Transmission Complete */ > @@ -110,6 +111,7 @@ 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; > }; > =20 > @@ -187,10 +189,13 @@ static void at91_init_twi_bus(struct at91_twi_d= ev *dev) > */ > static void at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_cl= k) > { > - int ckdiv, cdiv, div; > + int ckdiv, cdiv, div, hold =3D 0; > struct at91_twi_pdata *pdata =3D dev->pdata; > int offset =3D pdata->clk_offset; > int max_ckdiv =3D pdata->clk_max_div; > + u32 twd_hold_time_ns =3D 0; > + > +#define MAX_HOLD 31 Instead of here ^^ > =20 > div =3D max(0, (int)DIV_ROUND_UP(clk_get_rate(dev->clk), > 2 * twi_clk) - offset); > @@ -204,8 +209,33 @@ static void at91_calc_twi_clock(struct at91_twi_= dev *dev, int twi_clk) > cdiv =3D 255; > } > =20 > - dev->twi_cwgr_reg =3D (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 =3D HOLD + 3 x T_peripheral_clock > + * Use clk rate in kHz to prevent overflows when computing > + * hold. > + */ > + hold =3D DIV_ROUND_UP(twd_hold_time_ns > + * (clk_get_rate(dev->clk) / 1000), 1000000); > + hold -=3D 3; > + if (hold < 0) > + hold =3D 0; > + if (hold > MAX_HOLD) { > + dev_warn(dev->dev, > + "HOLD field set to its maximum value (%d instead of %d)\n", > + MAX_HOLD, hold); > + hold =3D MAX_HOLD; > + } > + } > + > + dev->twi_cwgr_reg =3D (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); > } > =20 > static void at91_twi_dma_cleanup(struct at91_twi_dev *dev) > @@ -797,6 +827,7 @@ static struct at91_twi_pdata at91rm9200_config =3D= { > .clk_offset =3D 3, > .has_unre_flag =3D true, > .has_alt_cmd =3D false, > + .has_hold_field =3D false, > }; > =20 > static struct at91_twi_pdata at91sam9261_config =3D { > @@ -804,6 +835,7 @@ static struct at91_twi_pdata at91sam9261_config =3D= { > .clk_offset =3D 4, > .has_unre_flag =3D false, > .has_alt_cmd =3D false, > + .has_hold_field =3D false, > }; > =20 > static struct at91_twi_pdata at91sam9260_config =3D { > @@ -811,6 +843,7 @@ static struct at91_twi_pdata at91sam9260_config =3D= { > .clk_offset =3D 4, > .has_unre_flag =3D false, > .has_alt_cmd =3D false, > + .has_hold_field =3D false, > }; > =20 > static struct at91_twi_pdata at91sam9g20_config =3D { > @@ -818,6 +851,7 @@ static struct at91_twi_pdata at91sam9g20_config =3D= { > .clk_offset =3D 4, > .has_unre_flag =3D false, > .has_alt_cmd =3D false, > + .has_hold_field =3D false, > }; > =20 > static struct at91_twi_pdata at91sam9g10_config =3D { > @@ -825,6 +859,7 @@ static struct at91_twi_pdata at91sam9g10_config =3D= { > .clk_offset =3D 4, > .has_unre_flag =3D false, > .has_alt_cmd =3D false, > + .has_hold_field =3D false, > }; > =20 > static const struct platform_device_id at91_twi_devtypes[] =3D { > @@ -854,6 +889,15 @@ static struct at91_twi_pdata at91sam9x5_config =3D= { > .clk_offset =3D 4, > .has_unre_flag =3D false, > .has_alt_cmd =3D false, > + .has_hold_field =3D false, > +}; > + > +static struct at91_twi_pdata sama5d4_config =3D { > + .clk_max_div =3D 7, > + .clk_offset =3D 4, > + .has_unre_flag =3D false, > + .has_alt_cmd =3D false, > + .has_hold_field =3D true, > }; > =20 > static struct at91_twi_pdata sama5d2_config =3D { > @@ -861,6 +905,7 @@ static struct at91_twi_pdata sama5d2_config =3D { > .clk_offset =3D 4, > .has_unre_flag =3D true, > .has_alt_cmd =3D true, > + .has_hold_field =3D true, > }; > =20 > static const struct of_device_id atmel_twi_dt_ids[] =3D { > @@ -883,6 +928,9 @@ static const struct of_device_id atmel_twi_dt_ids= [] =3D { > .compatible =3D "atmel,at91sam9x5-i2c", > .data =3D &at91sam9x5_config, > }, { > + .compatible =3D "atmel,sama5d4-i2c", > + .data =3D &sama5d4_config, > + }, { > .compatible =3D "atmel,sama5d2-i2c", > .data =3D &sama5d2_config, > }, { Otherwise it's okay for me. Bye, --=20 Nicolas Ferre