[PATCH] fbdev: ssd1307fb: Fix chargepump setting

[PATCH] fbdev: ssd1307fb: Fix chargepump setting

[Julian Scheel]

The charge pump setting must have bit D4 set all time according to the SSD1306
App Note. Instead of doing an logical and off shifted setting bit with 0x14 it
must be an logical or with 0x10 to ensure D4 is set.

Signed-off-by: Julian Scheel <julian@jusst.de>
---
 drivers/video/fbdev/ssd1307fb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index 1611215..5965a9b 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -389,7 +389,7 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
 		return ret;
 
 	ret = ssd1307fb_write_cmd(par->client,
-		(par->device_info->need_chargepump & 0x1 << 2) & 0x14);
+		0x10 | ((par->device_info->need_chargepump & 0x01) << 2));
 	if (ret < 0)
 		return ret;
 
-- 
2.6.2

[PATCH] fbdev: ssd1307fb: Fix chargepump setting

[Julian Scheel]

The charge pump setting must have bit D4 set all time according to the SSD1306
App Note. Instead of doing an logical and off shifted setting bit with 0x14 it
must be an logical or with 0x10 to ensure D4 is set.

Signed-off-by: Julian Scheel <julian@jusst.de>
---
 drivers/video/fbdev/ssd1307fb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index 1611215..5965a9b 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -389,7 +389,7 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
 		return ret;
 
 	ret = ssd1307fb_write_cmd(par->client,
-		(par->device_info->need_chargepump & 0x1 << 2) & 0x14);
+		0x10 | ((par->device_info->need_chargepump & 0x01) << 2));
 	if (ret < 0)
 		return ret;
 
-- 
2.6.2

Re: [PATCH] fbdev: ssd1307fb: Fix chargepump setting

[Julian Scheel]

On 15.11.15 14:36, Julian Scheel wrote:
> The charge pump setting must have bit D4 set all time according to the SSD1306
> App Note. Instead of doing an logical and off shifted setting bit with 0x14 it
> must be an logical or with 0x10 to ensure D4 is set.
>
> Signed-off-by: Julian Scheel <julian@jusst.de>
> ---
>   drivers/video/fbdev/ssd1307fb.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
> index 1611215..5965a9b 100644
> --- a/drivers/video/fbdev/ssd1307fb.c
> +++ b/drivers/video/fbdev/ssd1307fb.c
> @@ -389,7 +389,7 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
>   		return ret;
>
>   	ret = ssd1307fb_write_cmd(par->client,
> -		(par->device_info->need_chargepump & 0x1 << 2) & 0x14);
> +		0x10 | ((par->device_info->need_chargepump & 0x01) << 2));
>   	if (ret < 0)
>   		return ret;
>
>

+ Adding Jean-Christophe and Tomi in CC as maintainers and Thomas as the 
one who did last major changes to the driver.

Any objections on this patch?

Regards,
Julian

Re: [PATCH] fbdev: ssd1307fb: Fix chargepump setting

[Tomi Valkeinen]

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On 18/01/16 22:20, Julian Scheel wrote:
> On 15.11.15 14:36, Julian Scheel wrote:
>> The charge pump setting must have bit D4 set all time according to the
>> SSD1306
>> App Note. Instead of doing an logical and off shifted setting bit with
>> 0x14 it
>> must be an logical or with 0x10 to ensure D4 is set.

The code change looks ok, but I can't quite decipher the commit
description. "an logical and off shifted setting bit with 0x14"?

>> Signed-off-by: Julian Scheel <julian@jusst.de>
>> ---
>>   drivers/video/fbdev/ssd1307fb.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/video/fbdev/ssd1307fb.c
>> b/drivers/video/fbdev/ssd1307fb.c
>> index 1611215..5965a9b 100644
>> --- a/drivers/video/fbdev/ssd1307fb.c
>> +++ b/drivers/video/fbdev/ssd1307fb.c
>> @@ -389,7 +389,7 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
>>           return ret;
>>
>>       ret = ssd1307fb_write_cmd(par->client,
>> -        (par->device_info->need_chargepump & 0x1 << 2) & 0x14);
>> +        0x10 | ((par->device_info->need_chargepump & 0x01) << 2));

I presume 'need_chargepump' is really supposed to be a bool, instead of
int. And if it's really bool, something like this makes it more readable
to me:

BIT(4) | (par->device_info->need_chargepump ? BIT(2) : 0)

 Tomi


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Re: [PATCH] fbdev: ssd1307fb: Fix chargepump setting

[Julian Scheel]

Am 29.01.2016 um 12:55 schrieb Tomi Valkeinen:
>
> On 18/01/16 22:20, Julian Scheel wrote:
>> On 15.11.15 14:36, Julian Scheel wrote:
>>> The charge pump setting must have bit D4 set all time according to the
>>> SSD1306
>>> App Note. Instead of doing an logical and off shifted setting bit with
>>> 0x14 it
>>> must be an logical or with 0x10 to ensure D4 is set.
>
> The code change looks ok, but I can't quite decipher the commit
> description. "an logical and off shifted setting bit with 0x14"?

Appears I was not awake when writing the commit message. Besides that 
the sentence is really cludgy it must be "of" instead of "off".
It might be simplified to: "Applying logical and to 0x14 and the 
chargepump bit prevents bit 4 from being set. Fix it by or'ing bit 4 and 
the chargepump enable bit"

>>> Signed-off-by: Julian Scheel <julian@jusst.de>
>>> ---
>>>    drivers/video/fbdev/ssd1307fb.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/video/fbdev/ssd1307fb.c
>>> b/drivers/video/fbdev/ssd1307fb.c
>>> index 1611215..5965a9b 100644
>>> --- a/drivers/video/fbdev/ssd1307fb.c
>>> +++ b/drivers/video/fbdev/ssd1307fb.c
>>> @@ -389,7 +389,7 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
>>>            return ret;
>>>
>>>        ret = ssd1307fb_write_cmd(par->client,
>>> -        (par->device_info->need_chargepump & 0x1 << 2) & 0x14);
>>> +        0x10 | ((par->device_info->need_chargepump & 0x01) << 2));
>
> I presume 'need_chargepump' is really supposed to be a bool, instead of
> int. And if it's really bool, something like this makes it more readable
> to me:
>
> BIT(4) | (par->device_info->need_chargepump ? BIT(2) : 0)

Yes, this is easier to read.
Let me update the patch and send a v2.

-Julian