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Date: Wed, 25 Mar 2015 21:03:15 +0100
From: Thomas Niederprüm <niederp@...sik.uni-kl.de>
To: Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc: plagnioj@...osoft.com, tomi.valkeinen@...com,
kernel@...gutronix.de, shawn.guo@...aro.org, robh+dt@...nel.org,
linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv5 04/11] fbdev: ssd1307fb: Unify init code and obtain hw
specific bits from DT
Am Tue, 24 Mar 2015 15:14:28 -0700
schrieb Maxime Ripard <maxime.ripard@...e-electrons.com>:
> On Tue, Mar 24, 2015 at 10:23:51PM +0100, Thomas Niederprüm wrote:
> > The 130X controllers are very similar from the configuration point
> > of view. The configuration registers for the SSD1305/6/7 are bit
> > identical (except the the VHCOM register and the the default values
> > for clock setup register). This patch unifies the init code of the
> > controller and adds hardware specific properties to DT that are
> > needed to correctly initialize the device.
> >
> > The SSD130X can be wired to the OLED panel in various ways. Even
> > for the same controller this wiring can differ from one display
> > module to another and can not be probed by software. The added DT
> > properties reflect these hardware decisions of the display module
> > manufacturer. The 'com-sequential', 'com-lrremap' and 'com-invdir'
> > values define different possibilities for the COM signals pin
> > configuration and readout direction of the video memory. The
> > 'segment-no-remap' allows the inversion of the memory-to-pin
> > mapping ultimately inverting the order of the controllers output
> > pins. The 'prechargepX' values need to be adapted according to the
> > capacitance of the OLEDs pixel cells.
> >
> > So far these hardware specific bits are hard coded in the init
> > code, making the driver usable only for one certain wiring of the
> > controller. This patch makes the driver usable with all possible
> > hardware setups, given a valid hw description in DT. If these
> > values are not set in DT the default values, as they are set in the
> > ssd1307 init code right now, are used. This implies that without
> > the corresponding DT property "segment-no-remap" the segment remap
> > of the ssd130X controller gets activated. Even though this is not
> > the default behaviour according to the datasheet it maintains
> > backward compatibility with older DTBs.
> >
> > Note that the SSD1306 does not seem to be using the configuration
> > written to the registers at all. Therefore this patch does not try
> > to maintain these values without changes in DT. For reference an
> > example is added to the DT bindings documentation that reproduces
> > the configuration that is set in the current init code.
> >
> > Signed-off-by: Thomas Niederprüm <niederp@...sik.uni-kl.de>
> > ---
> > .../devicetree/bindings/video/ssd1307fb.txt | 21 +++
> > drivers/video/fbdev/ssd1307fb.c | 192
> > ++++++++++++--------- 2 files changed, 134 insertions(+), 79
> > deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/video/ssd1307fb.txt
> > b/Documentation/devicetree/bindings/video/ssd1307fb.txt index
> > 7a12542..637690f 100644 ---
> > a/Documentation/devicetree/bindings/video/ssd1307fb.txt +++
> > b/Documentation/devicetree/bindings/video/ssd1307fb.txt @@ -15,6
> > +15,16 @@ Required properties:
> > Optional properties:
> > - reset-active-low: Is the reset gpio is active on physical low?
> > + - solomon,segment-no-remap: Display needs normal (non-inverted)
> > data column
> > + to segment mapping
> > + - solomon,com-sequential: Display uses sequential COM pin
> > configuration
> > + - solomon,com-lrremap: Display uses left-right COM pin remap
> > + - solomon,com-invdir: Display uses inverted COM pin scan
> > direction
> > + - solomon,com-offset: Number of the COM pin wired to the first
> > display line
> > + - solomon,prechargep1: Length of deselect period (phase 1) in
> > clock cycles.
> > + - solomon,prechargep2: Length of precharge period (phase 2) in
> > clock cycles.
> > + This needs to be the higher, the higher
> > the capacitance
> > + of the OLED's pixels is
> >
> > [0]: Documentation/devicetree/bindings/pwm/pwm.txt
> >
> > @@ -26,3 +36,14 @@ ssd1307: oled@3c {
> > reset-gpios = <&gpio2 7>;
> > reset-active-low;
> > };
> > +
> > +ssd1306: oled@3c {
> > + compatible = "solomon,ssd1306fb-i2c";
> > + reg = <0x3c>;
> > + pwms = <&pwm 4 3000>;
> > + reset-gpios = <&gpio2 7>;
> > + reset-active-low;
> > + solomon,com-lrremap;
> > + solomon,com-invdir;
> > + solomon,com-offset = <32>;
> > +};
> > diff --git a/drivers/video/fbdev/ssd1307fb.c
> > b/drivers/video/fbdev/ssd1307fb.c index 8d34c56..d16aad4 100644
> > --- a/drivers/video/fbdev/ssd1307fb.c
> > +++ b/drivers/video/fbdev/ssd1307fb.c
> > @@ -40,20 +40,34 @@
> >
> > struct ssd1307fb_par;
> >
> > -struct ssd1307fb_ops {
> > - int (*init)(struct ssd1307fb_par *);
> > - int (*remove)(struct ssd1307fb_par *);
> > +struct ssd1307fb_deviceinfo {
> > + u32 default_vcomh;
> > + u32 default_dclk_div;
> > + u32 default_dclk_frq;
> > + int need_pwm;
> > + int need_chargepump;
> > };
> >
> > struct ssd1307fb_par {
> > + u32 com_invdir;
> > + u32 com_lrremap;
> > + u32 com_offset;
> > + u32 com_seq;
> > + u32 contrast;
> > + u32 dclk_div;
> > + u32 dclk_frq;
> > + struct ssd1307fb_deviceinfo *device_info;
> > struct i2c_client *client;
> > u32 height;
> > struct fb_info *info;
> > - struct ssd1307fb_ops *ops;
> > u32 page_offset;
> > + u32 prechargep1;
> > + u32 prechargep2;
> > struct pwm_device *pwm;
> > u32 pwm_period;
> > int reset;
> > + u32 seg_remap;
> > + u32 vcomh;
> > u32 width;
> > };
> >
> > @@ -254,69 +268,46 @@ static struct fb_deferred_io ssd1307fb_defio
> > = { .deferred_io = ssd1307fb_deferred_io,
> > };
> >
> > -static int ssd1307fb_ssd1307_init(struct ssd1307fb_par *par)
> > +static int ssd1307fb_init(struct ssd1307fb_par *par)
> > {
> > int ret;
> > + u32 precharge, dclk, com_invdir, compins;
> >
> > - par->pwm = pwm_get(&par->client->dev, NULL);
> > - if (IS_ERR(par->pwm)) {
> > - dev_err(&par->client->dev, "Could not get PWM from
> > device tree!\n");
> > - return PTR_ERR(par->pwm);
> > - }
> > -
> > - par->pwm_period = pwm_get_period(par->pwm);
> > - /* Enable the PWM */
> > - pwm_config(par->pwm, par->pwm_period / 2, par->pwm_period);
> > - pwm_enable(par->pwm);
> > -
> > - dev_dbg(&par->client->dev, "Using PWM%d with a %dns
> > period.\n",
> > - par->pwm->pwm, par->pwm_period);
> > -
> > - /* Map column 127 of the OLED to segment 0 */
> > - ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_SEG_REMAP_ON);
> > - if (ret < 0)
> > - return ret;
> > -
> > - /* Turn on the display */
> > - ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_DISPLAY_ON);
> > - if (ret < 0)
> > - return ret;
> > -
> > - return 0;
> > -}
> > -
> > -static int ssd1307fb_ssd1307_remove(struct ssd1307fb_par *par)
> > -{
> > - pwm_disable(par->pwm);
> > - pwm_put(par->pwm);
> > - return 0;
> > -}
> > + if (par->device_info->need_pwm) {
> > + par->pwm = pwm_get(&par->client->dev, NULL);
> > + if (IS_ERR(par->pwm)) {
> > + dev_err(&par->client->dev, "Could not get
> > PWM from device tree!\n");
> > + return PTR_ERR(par->pwm);
> > + }
> >
> > -static struct ssd1307fb_ops ssd1307fb_ssd1307_ops = {
> > - .init = ssd1307fb_ssd1307_init,
> > - .remove = ssd1307fb_ssd1307_remove,
> > -};
> > + par->pwm_period = pwm_get_period(par->pwm);
> > + /* Enable the PWM */
> > + pwm_config(par->pwm, par->pwm_period / 2,
> > par->pwm_period);
> > + pwm_enable(par->pwm);
> >
> > -static int ssd1307fb_ssd1306_init(struct ssd1307fb_par *par)
> > -{
> > - int ret;
> > + dev_dbg(&par->client->dev, "Using PWM%d with a
> > %dns period.\n",
> > + par->pwm->pwm, par->pwm_period);
> > + };
> >
> > /* Set initial contrast */
> > ret = ssd1307fb_write_cmd(par->client, SSD1307FB_CONTRAST);
> > if (ret < 0)
> > return ret;
> >
> > - ret = ssd1307fb_write_cmd(par->client, 0x7f);
> > - if (ret < 0)
> > - return ret;
> > -
> > - /* Set COM direction */
> > - ret = ssd1307fb_write_cmd(par->client, 0xc8);
> > + ret = ssd1307fb_write_cmd(par->client, par->contrast);
> > if (ret < 0)
> > return ret;
> >
> > /* Set segment re-map */
> > - ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_SEG_REMAP_ON);
> > + if (par->seg_remap) {
> > + ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_SEG_REMAP_ON);
> > + if (ret < 0)
> > + return ret;
> > + };
> > +
> > + /* Set COM direction */
> > + com_invdir = 0xc0 | (par->com_invdir & 0xf) << 3;
> > + ret = ssd1307fb_write_cmd(par->client, com_invdir);
> > if (ret < 0)
> > return ret;
> >
> > @@ -334,7 +325,7 @@ static int ssd1307fb_ssd1306_init(struct
> > ssd1307fb_par *par) if (ret < 0)
> > return ret;
> >
> > - ret = ssd1307fb_write_cmd(par->client, 0x20);
> > + ret = ssd1307fb_write_cmd(par->client, par->com_offset);
> > if (ret < 0)
> > return ret;
> >
> > @@ -343,7 +334,8 @@ static int ssd1307fb_ssd1306_init(struct
> > ssd1307fb_par *par) if (ret < 0)
> > return ret;
> >
> > - ret = ssd1307fb_write_cmd(par->client, 0xf0);
> > + dclk = (par->dclk_div & 0xf) | (par->dclk_frq & 0xf) << 4;
> > + ret = ssd1307fb_write_cmd(par->client, dclk);
> > if (ret < 0)
> > return ret;
> >
> > @@ -352,7 +344,8 @@ static int ssd1307fb_ssd1306_init(struct
> > ssd1307fb_par *par) if (ret < 0)
> > return ret;
> >
> > - ret = ssd1307fb_write_cmd(par->client, 0x22);
> > + precharge = (par->prechargep1 & 0xf) | (par->prechargep2 &
> > 0xf) << 4;
> > + ret = ssd1307fb_write_cmd(par->client, precharge);
> > if (ret < 0)
> > return ret;
> >
> > @@ -361,7 +354,9 @@ static int ssd1307fb_ssd1306_init(struct
> > ssd1307fb_par *par) if (ret < 0)
> > return ret;
> >
> > - ret = ssd1307fb_write_cmd(par->client, 0x22);
> > + compins = 0x02 | (!par->com_seq & 0x1) << 4
> > + | (par->com_lrremap & 0x1) << 5;
> > + ret = ssd1307fb_write_cmd(par->client, compins);
> > if (ret < 0)
> > return ret;
> >
> > @@ -370,18 +365,20 @@ static int ssd1307fb_ssd1306_init(struct
> > ssd1307fb_par *par) if (ret < 0)
> > return ret;
> >
> > - ret = ssd1307fb_write_cmd(par->client, 0x49);
> > + ret = ssd1307fb_write_cmd(par->client, par->vcomh);
> > if (ret < 0)
> > return ret;
> >
> > - /* Turn on the DC-DC Charge Pump */
> > - ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_CHARGE_PUMP);
> > - if (ret < 0)
> > - return ret;
> > + if (par->device_info->need_chargepump) {
> > + /* Turn on the DC-DC Charge Pump */
> > + ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_CHARGE_PUMP);
> > + if (ret < 0)
> > + return ret;
> >
> > - ret = ssd1307fb_write_cmd(par->client, 0x14);
> > - if (ret < 0)
> > - return ret;
> > + ret = ssd1307fb_write_cmd(par->client, 0x14);
> > + if (ret < 0)
> > + return ret;
> > + };
> >
> > /* Switch to horizontal addressing mode */
> > ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_SET_ADDRESS_MODE); @@ -393,6 +390,7 @@ static int
> > ssd1307fb_ssd1306_init(struct ssd1307fb_par *par) if (ret < 0)
> > return ret;
> >
> > + /* Set column range */
> > ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_SET_COL_RANGE); if (ret < 0)
> > return ret;
> > @@ -405,6 +403,7 @@ static int ssd1307fb_ssd1306_init(struct
> > ssd1307fb_par *par) if (ret < 0)
> > return ret;
> >
> > + /* Set page range */
> > ret = ssd1307fb_write_cmd(par->client,
> > SSD1307FB_SET_PAGE_RANGE); if (ret < 0)
> > return ret;
> > @@ -426,18 +425,30 @@ static int ssd1307fb_ssd1306_init(struct
> > ssd1307fb_par *par) return 0;
> > }
> >
> > -static struct ssd1307fb_ops ssd1307fb_ssd1306_ops = {
> > - .init = ssd1307fb_ssd1306_init,
> > +static struct ssd1307fb_deviceinfo ssd1307fb_ssd1306_deviceinfo = {
> > + .default_vcomh = 0x20,
> > + .default_dclk_div = 0,
>
> A division by 0 ?
default_dclk_div stores the bit value for the divider register. The
bit encodes the divider as follows: bit = (divider - 1). But I guess
your are right that it makes more sense to store the actual divider
here and just calculate the bit value when writing to the device.
>
> > + .default_dclk_frq = 8,
> > + .need_pwm = 0,
>
> You don't need to declare this field, its value will already be
> initialized to 0.
I wasn't sure whether this is necessarily the case. But your hint and
a bit more reading on initialization of static structs convinced me. I
will remove the unnecessary fields.
Thomas
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