Message-ID: <CAOiHx=nmsAh3ADL3s0eZKpEZJqCB_POi=8YjfxrHYLEbjRfwHg@mail.gmail.com>
Date:   Mon, 6 Mar 2023 21:00:44 +0100
From:   Jonas Gorski <jonas.gorski@...il.com>
To:     Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>
Cc:     broonie@...nel.org, miquel.raynal@...tlin.com, richard@....at,
        vigneshr@...com, jic23@...nel.org, tudor.ambarus@...rochip.com,
        pratyush@...nel.org, Sanju.Mehta@....com,
        chin-ting_kuo@...eedtech.com, clg@...d.org, kdasu.kdev@...il.com,
        f.fainelli@...il.com, rjui@...adcom.com, sbranden@...adcom.com,
        eajames@...ux.ibm.com, olteanv@...il.com, han.xu@....com,
        john.garry@...wei.com, shawnguo@...nel.org, s.hauer@...gutronix.de,
        narmstrong@...libre.com, khilman@...libre.com,
        matthias.bgg@...il.com, haibo.chen@....com,
        linus.walleij@...aro.org, daniel@...que.org,
        haojian.zhuang@...il.com, robert.jarzmik@...e.fr,
        agross@...nel.org, bjorn.andersson@...aro.org, heiko@...ech.de,
        krzysztof.kozlowski@...aro.org, andi@...zian.org,
        mcoquelin.stm32@...il.com, alexandre.torgue@...s.st.com,
        wens@...e.org, jernej.skrabec@...il.com, samuel@...lland.org,
        masahisa.kojima@...aro.org, jaswinder.singh@...aro.org,
        rostedt@...dmis.org, mingo@...hat.com, l.stelmach@...sung.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, alex.aring@...il.com, stefan@...enfreihafen.org,
        kvalo@...nel.org, james.schulman@...rus.com,
        david.rhodes@...rus.com, tanureal@...nsource.cirrus.com,
        rf@...nsource.cirrus.com, perex@...ex.cz, tiwai@...e.com,
        npiggin@...il.com, christophe.leroy@...roup.eu, mpe@...erman.id.au,
        oss@...error.net, windhl@....com, yangyingliang@...wei.com,
        william.zhang@...adcom.com, kursad.oney@...adcom.com,
        anand.gore@...adcom.com, rafal@...ecki.pl, git@....com,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        joel@....id.au, andrew@...id.au, radu_nicolae.pirea@....ro,
        nicolas.ferre@...rochip.com, alexandre.belloni@...tlin.com,
        claudiu.beznea@...rochip.com,
        bcm-kernel-feedback-list@...adcom.com, fancer.lancer@...il.com,
        kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
        jbrunet@...libre.com, martin.blumenstingl@...glemail.com,
        avifishman70@...il.com, tmaimon77@...il.com, tali.perry1@...il.com,
        venture@...gle.com, yuenn@...gle.com, benjaminfair@...gle.com,
        yogeshgaur.83@...il.com, konrad.dybcio@...ainline.org,
        alim.akhtar@...sung.com, ldewangan@...dia.com,
        thierry.reding@...il.com, jonathanh@...dia.com,
        michal.simek@....com, linux-aspeed@...ts.ozlabs.org,
        openbmc@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
        linux-rockchip@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-sunxi@...ts.linux.dev, linux-tegra@...r.kernel.org,
        netdev@...r.kernel.org, linux-wpan@...r.kernel.org,
        libertas-dev@...ts.infradead.org, linux-wireless@...r.kernel.org,
        linux-mtd@...ts.infradead.org, lars@...afoo.de,
        Michael.Hennerich@...log.com, linux-iio@...r.kernel.org,
        michael@...le.cc, palmer@...belt.com,
        linux-riscv@...ts.infradead.org, alsa-devel@...a-project.org,
        patches@...nsource.cirrus.com, linuxppc-dev@...ts.ozlabs.org,
        amitrkcian2002@...il.com
Subject: Re: [PATCH V5 09/15] spi: Add stacked and parallel memories support
 in SPI core

Hi,

On Mon, 6 Mar 2023 at 18:26, Amit Kumar Mahapatra
<amit.kumar-mahapatra@....com> wrote:
>
> For supporting multiple CS the SPI device need to be aware of all the CS
> values. So, the "chip_select" member in the spi_device structure is now an
> array that holds all the CS values.
>
> spi_device structure now has a "cs_index_mask" member. This acts as an
> index to the chip_select array. If nth bit of spi->cs_index_mask is set
> then the driver would assert spi->chip_select[n].
>
> In parallel mode all the chip selects are asserted/de-asserted
> simultaneously and each byte of data is stored in both devices, the even
> bits in one, the odd bits in the other. The split is automatically handled
> by the GQSPI controller. The GQSPI controller supports a maximum of two
> flashes connected in parallel mode. A "multi-cs-cap" flag is added in the
> spi controntroller data, through ctlr->multi-cs-cap the spi core will make
> sure that the controller is capable of handling multiple chip selects at
> once.
>
> For supporting multiple CS via GPIO the cs_gpiod member of the spi_device
> structure is now an array that holds the gpio descriptor for each
> chipselect.
>
> Multi CS support using GPIO is not tested due to unavailability of
> necessary hardware setup.
>
> Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>
> ---
>  drivers/spi/spi.c       | 213 +++++++++++++++++++++++++++-------------
>  include/linux/spi/spi.h |  34 +++++--
>  2 files changed, 173 insertions(+), 74 deletions(-)
>
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 5866bf5813a4..8ec7f58fa111 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -613,7 +613,8 @@ static int spi_dev_check(struct device *dev, void *data)
>         struct spi_device *new_spi = data;
>
>         if (spi->controller == new_spi->controller &&
> -           spi_get_chipselect(spi, 0) == spi_get_chipselect(new_spi, 0))
> +           spi_get_chipselect(spi, 0) == spi_get_chipselect(new_spi, 0) &&
> +           spi_get_chipselect(spi, 1) == spi_get_chipselect(new_spi, 1))
>                 return -EBUSY;

This will only reject new devices if both chip selects are identical,
but not if they only share one, e.g. CS 1 + 2 vs 1 + 3, or 1 + 2 vs
only 2, or if the order is different (1 + 2 vs 2 + 1 - haven't read
the code too close to know if this is allowed/possible).

Regards,
Jonas

Powered by blists - more mailing lists