From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Ungerer Subject: Re: [PATCHv3 1/2] spi: imx: fix use of native chip-selects with devicetree Date: Wed, 9 Aug 2017 23:00:55 +1000 Message-ID: <239ae959-ce96-711b-dbfb-4e892b7eab3b@linux-m68k.org> References: <1499746932-14850-1-git-send-email-gerg@linux-m68k.org> <1499746932-14850-2-git-send-email-gerg@linux-m68k.org> <20170720063449.qvi3s7faapcncoqm@pengutronix.de> <2892f819-f1a2-b68d-be01-e8ac7f4b4222@linux-m68k.org> <20170724062147.o7tccwskxfuls3ej@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Fabio Estevam , Mark Brown , Sascha Hauer , "linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" To: Oleksij Rempel Return-path: In-Reply-To: <20170724062147.o7tccwskxfuls3ej-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> Content-Language: en-US Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Hi Qleksij, On 24/07/17 16:21, Oleksij Rempel wrote: > On Thu, Jul 20, 2017 at 11:00:49PM +1000, Greg Ungerer wrote: >> Hi Oleksij, >> >> On 20/07/17 16:34, Oleksij Rempel wrote: >>> Hi Greg, >>> >>> On Tue, Jul 18, 2017 at 09:53:58PM -0300, Fabio Estevam wrote: >>>> Adding Pengutronix folks on Cc. >>>> >>>> On Tue, Jul 11, 2017 at 1:22 AM, Greg Ungerer wrote: >>>>> The commonly used mechanism of specifying the hardware or native >>>>> chip-select on an SPI device in devicetree (that is "cs-gpios = <0>") >>>>> does not result in the native chip-select being configured for use. >>>>> So external SPI devices that require use of the native chip-select >>>>> will not work. >>>>> >>>>> You can successfully specify native chip-selects if using a platform >>>>> setup by specifying the cs-gpio as negative offset by 32. And that >>>>> works correctly. You cannot use the same method in devicetree. >>>>> >>>>> The logic in the spi-imx.c driver during probe uses core spi function >>>>> of_spi_register_master() in spi.c to parse the "cs-gpios" devicetree tag. >>>>> For valid GPIO values that will be recorded for use, all other entries in >>>>> the cs_gpios list will be set to -ENOENT. So entries like "<0>" will be >>>>> set to -ENOENT in the cs_gpios list. >>>>> >>>>> When the SPI device registers are setup the code will use the GPIO >>>>> listed in the cs_gpios list for the desired chip-select. If the cs_gpio >>>>> is less then 0 then it is intended to be for a native chip-select, and >>>>> its cs_gpio value is added to 32 to get the chipselect number to use. >>>>> Problem is that with devicetree this can only ever be -ENOENT (which >>>>> is -2), and that alone results in an invalid chip-select number. But also >>>>> doesn't allow selection of the native chip-select at all. >>>>> >>>>> To fix, if the cs_gpio specified for this spi device is not a >>>>> valid GPIO then use the "chip_select" (that is the native chip-select >>>>> number) for hardware setup. >>>>> >>>>> Signed-off-by: Greg Ungerer >>>>> --- >>>>> drivers/spi/spi-imx.c | 8 ++++---- >>>>> 1 file changed, 4 insertions(+), 4 deletions(-) >>>>> >>>>> diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c >>>>> index b402530..f4fe66c 100644 >>>>> --- a/drivers/spi/spi-imx.c >>>>> +++ b/drivers/spi/spi-imx.c >>>>> @@ -524,8 +524,8 @@ static int mx31_config(struct spi_device *spi, struct spi_imx_config *config) >>>>> reg |= MX31_CSPICTRL_POL; >>>>> if (spi->mode & SPI_CS_HIGH) >>>>> reg |= MX31_CSPICTRL_SSPOL; >>>>> - if (spi->cs_gpio < 0) >>>>> - reg |= (spi->cs_gpio + 32) << >>>>> + if (!gpio_is_valid(spi->cs_gpio)) >>>>> + reg |= (spi->chip_select) << >>>>> (is_imx35_cspi(spi_imx) ? MX35_CSPICTRL_CS_SHIFT : >>>>> MX31_CSPICTRL_CS_SHIFT); >>>>> >>>>> @@ -616,8 +616,8 @@ static int mx21_config(struct spi_device *spi, struct spi_imx_config *config) >>>>> reg |= MX21_CSPICTRL_POL; >>>>> if (spi->mode & SPI_CS_HIGH) >>>>> reg |= MX21_CSPICTRL_SSPOL; >>>>> - if (spi->cs_gpio < 0) >>>>> - reg |= (spi->cs_gpio + 32) << MX21_CSPICTRL_CS_SHIFT; >>>>> + if (!gpio_is_valid(spi->cs_gpio)) >>>>> + reg |= spi->chip_select << MX21_CSPICTRL_CS_SHIFT; >>>>> >>>>> writel(reg, spi_imx->base + MXC_CSPICTRL); >>>>> >>> >>> hm... do I see this correctly, all native chip_selects should >>> be registered before gpio based CS? >> >> I don't follow. The "<0>" must be in the position in the list where >> you want to use the native chip select. You can't arbitrarily change >> the order. >> >> >>> For example like this? >>> cs-gpios = <0>, <&gpio1 1 0>, <&gpio1 2 0>; >>> >>> Looks like we don't have any sanity checks for this kind of >>> configuration: >>> cs-gpios = <&gpio1 1 0>, <&gpio1 2 0>, <0>; >> >> The chip_select is sanity checked in spi_add_device(). >> >> >>> We may shift some wired numbers here: >>> reg |= spi->chip_select << MX21_CSPICTRL_CS_SHIFT; >> >> I am not sure I see how that can be the case? > > old and new version of iMX have different amount of native CS. > I can't find the code which is actually checking if we use right native > CS-index. > May be i'm blind :) I don't think I entirely understand what you are saying. The code at the top of spi_add_device() [drivers/spi/spi.c] looks like this: /* Chipselects are numbered 0..max; validate. */ if (spi->chip_select >= ctlr->num_chipselect) { dev_err(dev, "cs%d >= max %d\n", spi->chip_select, ctlr->num_chipselect); return -EINVAL; } So it will range check the spi device (spi->chip_select) to be within the range valid for this SPI controller. That is the very same spi->chip_select that is used in spi-imx.c to set the register bits when using a native chip select. Regards Greg -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html