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([2a00:1fa0:631:be36:41f9:a0d4:22df:3c65]) by smtp.gmail.com with ESMTPSA id i1sm9597287lji.71.2020.03.01.02.04.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 01 Mar 2020 02:04:09 -0800 (PST) Subject: Re: [PATCH RFC 1/3] spi: Allow SPI controller override device buswidth To: John Garry , broonie@kernel.org Cc: linux-spi@vger.kernel.org, linuxarm@huawei.com, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, andriy.shevchenko@linux.intel.com References: <1582903131-160033-1-git-send-email-john.garry@huawei.com> <1582903131-160033-2-git-send-email-john.garry@huawei.com> From: Sergei Shtylyov Message-ID: <52ecb988-d842-c04b-a0e8-93e8850009c4@cogentembedded.com> Date: Sun, 1 Mar 2020 13:04:07 +0300 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <1582903131-160033-2-git-send-email-john.garry@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello! On 28.02.2020 18:18, John Garry wrote: > Currently ACPI firmware description for a SPI device does not have any > method to describe the data buswidth on the board. > > So even through the controller and device may support higher modes than ^^^^^^^ Though? > standard SPI, it cannot be assumed that the board does - as such, that > device is limited to standard SPI in such a circumstance. > > As a workaround, allow the controller driver supply buswidth override bits, > which are used inform the core code that the controller driver knows the > buswidth supported on that board for that device. > > A host controller driver might know this info from DMI tables, for example. > > Signed-off-by: John Garry > --- > drivers/spi/spi.c | 4 +++- > include/linux/spi/spi.h | 3 +++ > 2 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c > index 38b4c78df506..292f26807b41 100644 > --- a/drivers/spi/spi.c > +++ b/drivers/spi/spi.c > @@ -510,6 +510,7 @@ struct spi_device *spi_alloc_device(struct spi_controller *ctlr) > spi->dev.bus = &spi_bus_type; > spi->dev.release = spidev_release; > spi->cs_gpio = -ENOENT; > + spi->mode = ctlr->buswidth_override_bits; > > spin_lock_init(&spi->statistics.lock); > > @@ -2181,9 +2182,10 @@ static acpi_status acpi_register_spi_device(struct spi_controller *ctlr, > return AE_NO_MEMORY; > } > > + What for? > ACPI_COMPANION_SET(&spi->dev, adev); > spi->max_speed_hz = lookup.max_speed_hz; > - spi->mode = lookup.mode; > + spi->mode |= lookup.mode; > spi->irq = lookup.irq; > spi->bits_per_word = lookup.bits_per_word; > spi->chip_select = lookup.chip_select; [...] MBR, Sergei