linux-kernel - Re: [PATCH v2] spi: Setup the master controller driver before setting the chipselect

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Date:	Fri, 16 Oct 2015 10:47:27 -0500
From:	"Franklin S Cooper Jr." <fcooper@...com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	<linux-spi@...r.kernel.org>, Mark Brown <broonie@...nel.org>,
	Sekhar Nori <nsekhar@...com>, <ssantosh@...nel.org>,
	"Ivan T. Ivanov" <iivanov@...sol.com>, <m-karicheri2@...com>,
	"Ivan T. Ivanov" <iivanov.xz@...il.com>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	<hkallweit1@...il.com>
Subject: Re: [PATCH v2] spi: Setup the master controller driver before setting
 the chipselect



On 10/16/2015 10:45 AM, Andy Shevchenko wrote:
> On Fri, Oct 16, 2015 at 6:29 PM, Franklin S Cooper Jr <fcooper@...com> wrote:
>> SPI controllers may need to be properly setup before chip selects
>> can be used. Therefore, wait until the spi controller has a chance
>> to perform their setup procedure before trying to use the chip
>> select.
>>
>> This also insures that the chip selects pins are in a good
>> state before asseting them which otherwise may cause confusion.
>>
>> Signed-off-by: Franklin S Cooper Jr <fcooper@...com>
> Does it mean I have to test it again?
Oops sorry. No the patch hasn't changed. I can shoot a v3 with your tested by included.
>
>> ---
>> Keystone 2 devices currently fail to boot in linux-next after the
>> below commit was applied:
>>
>> spi: bitbang: switch to the generic implementation of transfer_one_message
>> commit: 0037686596832572bbca05ab168d9884d7d704c1
>>
>> This patch allows Keystone 2 devices to boot again in linux-next.
>>
>> Tested this patch on K2E evm and am437 starterkit which both have SPI
>> devices to insure regressions aren't seen.
>>
>> V2 Changes:
>> Update commit message.
>>
>>  drivers/spi/spi.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
>> index 4c638f3..9d5525a 100644
>> --- a/drivers/spi/spi.c
>> +++ b/drivers/spi/spi.c
>> @@ -2059,11 +2059,11 @@ int spi_setup(struct spi_device *spi)
>>         if (!spi->max_speed_hz)
>>                 spi->max_speed_hz = spi->master->max_speed_hz;
>>
>> -       spi_set_cs(spi, false);
>> -
>>         if (spi->master->setup)
>>                 status = spi->master->setup(spi);
>>
>> +       spi_set_cs(spi, false);
>> +
>>         dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s%u bits/w, %u Hz max --> %d\n",
>>                         (int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
>>                         (spi->mode & SPI_CS_HIGH) ? "cs_high, " : "",
>> --
>> 2.6.1
>>
>
>

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