Messages in this thread | | | Date | Tue, 19 May 2020 11:29:17 +0200 | From | Lars Povlsen <> | Subject | Re: [PATCH 07/10] spi: spi-dw-mchp: Add Sparx5 support |
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[Sorry about the slight delay on getting back on this]
On 14/05/20 11:25, Mark Brown wrote:
> Date: Thu, 14 May 2020 11:25:16 +0100 > From: Mark Brown <broonie@kernel.org> > To: Lars Povlsen <lars.povlsen@microchip.com> > Cc: SoC Team <soc@kernel.org>, Microchip Linux Driver Support > <UNGLinuxDriver@microchip.com>, linux-spi@vger.kernel.org, > devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, > linux-arm-kernel@lists.infradead.org, Alexandre Belloni > <alexandre.belloni@bootlin.com> > Subject: Re: [PATCH 07/10] spi: spi-dw-mchp: Add Sparx5 support > User-Agent: Mutt/1.10.1 (2018-07-13) > > On Wed, May 13, 2020 at 04:00:28PM +0200, Lars Povlsen wrote: > > > +static void dw_spi_mchp_set_cs_owner(struct dw_spi_mchp *dwsmchp, > > + const struct dw_spi_mchp_props *props, > > + u8 cs, u8 owner) > > { > > + u8 dummy = (owner == MSCC_IF_SI_OWNER_SIBM ? > > + MSCC_IF_SI_OWNER_SIMC : MSCC_IF_SI_OWNER_SIBM); > > Please write normal conditional statements to improve legibility. >
I will take your recommendation to heart.
> > +static void dw_spi_mchp_set_cs(struct spi_device *spi, bool nEnable) > > +{ > > + bool enable = !nEnable; /* This keeps changing in the API... */ > > No, it doesn't. The API has not changed for more than a decade. >
I will remove the comment.
I think the comment was related to when we got bitten by the below change, but alas.
commit ada9e3fcc175db4538f5b5e05abf5dedf626e550 Author: Charles Keepax <ckeepax@opensource.cirrus.com> Date: Wed Nov 27 15:39:36 2019 +0000
spi: dw: Correct handling of native chipselect
This patch reverts commit 6e0a32d6f376 ("spi: dw: Fix default polarity of native chipselect"). > > + } else if (props->ss_force_ena_off) { > > + if (enable) { > > + /* Ensure CS toggles, so start off all disabled */ > > + regmap_write(dwsmchp->syscon, props->ss_force_val_off, > > + ~0); > > What's all this force_ena_off stuff about? The controller should not be > making decisions about management of the chip select, this will break > users. >
Our controller is not using DMA, but the FIFO interface. And as the DW controller drops CS when the FIFO runs empty, this will upset SPI devices. The "ss_force" is something the HW designes put on top to "override" the CS. We could of course use the GPIO's specifically to overcome this - but the "boot" CS 0 is a builtin CS, with no underlying GPIO.
Add to this that the HW dept decided to add *2* physical SPI busses to the same controller. That we also need to switch between. And ensure CS gets dropped correctly before changing tracks...
Long story, lot of grief...
> > + if (pdev->dev.of_node) { > > + int i; > > + > > + for (i = 0; i < dws->num_cs; i++) { > > + int cs_gpio = of_get_named_gpio(pdev->dev.of_node, > > + "cs-gpios", i); > > + > > + if (cs_gpio == -EPROBE_DEFER) { > > + ret = cs_gpio; > > + goto out; > > + } > > + > > + if (gpio_is_valid(cs_gpio)) { > > + ret = devm_gpio_request(&pdev->dev, cs_gpio, > > + dev_name(&pdev->dev)); > > + if (ret) > > + goto out; > > Set use_gpio_descriptors and let the core manage the GPIO.
Good suggestion, just the ticket!
And thank you very much for your time & comments.
---Lars
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