linux-kernel - Re: [PATCH v2 03/13] spi: dw: Add support for Pensando Elba SoC SPI

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Date:   Sun, 22 Aug 2021 18:26:56 -0700
From:   Brad Larson <brad@...sando.io>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Mark Brown <broonie@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Olof Johansson <olof@...om.net>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 03/13] spi: dw: Add support for Pensando Elba SoC SPI

Hi Sergey,

On Wed, Mar 31, 2021 at 11:00 AM Serge Semin <fancer.lancer@...il.com> wrote:
>
> On Sun, Mar 28, 2021 at 06:59:28PM -0700, Brad Larson wrote:
> > The Pensando Elba SoC uses a GPIO based chip select
> > for two DW SPI busses with each bus having two
> > chip selects.
(...)
> > +static void dw_spi_elba_set_cs(struct spi_device *spi, bool enable)
> > +{
> > +     struct dw_spi *dws = spi_master_get_devdata(spi->master);
> > +
>
> > +     if (!enable) {
>
> Please, be more attentive to the review-comments given to you before
> resending a new patchset. One more time. This version of set_cs won't
> work for Active-high CS. Each SPI controller working with GPIO-based
> chip-select is marked as supporting that feature. So your DW
> SPI controller won't be able to work correctly with SPI-devices
> activated by active-high chip-select signal. Note default
> dw_spi_set_cs() callback supports that.

Thanks for your patience.  It took me a while to understand what you
were asking about regarding dw_spi_set_cs() due to the unnecessarily
complicated function that was being used.  The current implementation
I propose for v3 patchset is this which as you identified handles cs
active high/low properly.

static void dw_spi_elba_set_cs(struct spi_device *spi, bool enable)
{
        spi->chip_select = 0;
        dw_spi_set_cs(spi, enable);
}

Regards,
Brad