linux-kernel - Re: [PATCH v5 5/7] gpio: pca953x: fix address calculation for pcal6524

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Message-Id: <4F016FCD-04B0-4EE1-A9F4-5A182DD437EF@goldelico.com>
Date:   Wed, 2 May 2018 14:35:24 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Kumar Gala <galak@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>,
        Pawel Moll <pawel.moll@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ian Campbell <ijc+devicetree@...lion.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, kernel@...a-handheld.com
Subject: Re: [PATCH v5 5/7] gpio: pca953x: fix address calculation for pcal6524

Hi Andy,

> Am 02.05.2018 um 14:28 schrieb Andy Shevchenko <andy.shevchenko@...il.com>:
> 
> On Sat, Apr 28, 2018 at 7:31 PM, H. Nikolaus Schaller <hns@...delico.com> wrote:
>> The register constants are so far defined in a way that they fit
>> for the pcal9555a when shifted by the number of banks, i.e. are
>> multiplied by 2 in the accessor function.
>> 
>> Now, the pcal6524 has 3 banks which means the relative offset
>> is multiplied by 4 for the standard registers.
>> 
>> Simply applying the bit shift to the extended registers gives
>> a wrong result, since the base offset is already included in
>> the offset.
>> 
>> Therefore, we add code to the 24 bit accessor functions to
>> adjust the register number for these exended registers.
>> 
> 
> Suggested-by ?

Detecting that we need to adjust the registers generally was from me,
but your suggestion of an improved formula should of course be mentioned
and appreciated!

I'll think about a good formulation for v6.

BR and thanks,
Nikolaus

> 
>> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
>> ---
>> drivers/gpio/gpio-pca953x.c | 8 ++++++--
>> 1 file changed, 6 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
>> index fc863faa3ce4..4194495a7990 100644
>> --- a/drivers/gpio/gpio-pca953x.c
>> +++ b/drivers/gpio/gpio-pca953x.c
>> @@ -221,9 +221,11 @@ static int pca957x_write_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
>> static int pca953x_write_regs_24(struct pca953x_chip *chip, int reg, u8 *val)
>> {
>>        int bank_shift = fls((chip->gpio_chip.ngpio - 1) / BANK_SZ);
>> +       int addr = (reg & PCAL_GPIO_MASK) << bank_shift;
>> +       int pinctrl = (reg & PCAL_PINCTRL_MASK) << 1;
>> 
>>        return i2c_smbus_write_i2c_block_data(chip->client,
>> -                                             (reg << bank_shift) | REG_ADDR_AI,
>> +                                             pinctrl | addr | REG_ADDR_AI,
>>                                              NBANK(chip), val);
>> }
>> 
>> @@ -263,9 +265,11 @@ static int pca953x_read_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
>> static int pca953x_read_regs_24(struct pca953x_chip *chip, int reg, u8 *val)
>> {
>>        int bank_shift = fls((chip->gpio_chip.ngpio - 1) / BANK_SZ);
>> +       int addr = (reg & PCAL_GPIO_MASK) << bank_shift;
>> +       int pinctrl = (reg & PCAL_PINCTRL_MASK) << 1;
>> 
>>        return i2c_smbus_read_i2c_block_data(chip->client,
>> -                                            (reg << bank_shift) | REG_ADDR_AI,
>> +                                            pinctrl | addr | REG_ADDR_AI,
>>                                             NBANK(chip), val);
>> }
>> 
>> --
>> 2.12.2
>> 
> 
> 
> 
> -- 
> With Best Regards,
> Andy Shevchenko