From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 23385C624D0 for ; Wed, 2 Sep 2026 04:55:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=0Bq3n+d6CqRiWka+r6Puyq82APtewnlh2hBeOLFbC3w=; b=uMXLuSJQc7xz1gUFaA4OUqv9MF VcwlAAvoMo2C+7eN9vU561W5Za8EJESsHth7xUr7l8nvsmSIePVsvhGSzXr3b7ampK62SO0Xok4+C 9CgF0NzcKKXdYK3LwTlhh0UlZI54k+MdlanXVt7FNt3ocXK0xQMtk9PfO0ioypbwFHcDyucPKG9MH q2+52Ol2UGhBOb00EcxUOylF//fPtfyL8cTiIGwGsXSQ7FU2YOA6G3frKlE6gxZ4RNy1l5Kw+P5pa DcwdyGa1+2MzZPWKzWxQHu9ESRmEfFMrJ8H+zKEthdn8lfqA+1j85riD6UraXqKieWMYDaZ1C172w ZggjFBpQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x1d0B-0000000Dmo3-2yWz; Wed, 02 Sep 2026 04:55:11 +0000 Received: from mx.nabladev.com ([2a00:f820:417:0:178:251:229:89]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x1d09-0000000Dmnc-2Cxv for linux-arm-kernel@lists.infradead.org; Wed, 02 Sep 2026 04:55:11 +0000 Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 1188A11D4B1; Wed, 02 Sep 2026 06:54:55 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nabladev.com; s=dkim; t=1788324898; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:content-language:in-reply-to:references; bh=0Bq3n+d6CqRiWka+r6Puyq82APtewnlh2hBeOLFbC3w=; b=SGde+sPNe3xV7Zvq3omYCHqKEviYf3ImreWf67FsFcpVfK8ba7uKTmKD/t1cdTz7OBrDVr xDwsRYs1brjC8zgueF/G26DeI5AKj0IKpD6k5SwN/0iDw2A4AdE11CpxEsKCEHQbNOjXqN th+7z0KqS1s2tFAVNq1FGi9kifc/xwjMJEyFzJjtnSnQL2RgsdxgHnHVUrzGDlBUvsgkM6 4898Cb3e+yA9hcnVgpCpahwgM917+137PJfNH9wQmi8v6qO1m3jTraWv5zq/APdqcQiYQM V2rUwv9+cB7C1dNdcTsHb3LRc3MGi+tKLqLbCLUYG/5T8Xlnuuu2Tyi/9n8EMA== Message-ID: Date: Wed, 2 Sep 2026 06:54:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH v4] driver: fpga: xilinx-selectmap: add csi and rdwr support Content-Language: en-US To: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-fpga@vger.kernel.org, Bartosz Golaszewski , Linus Walleij , Michal Simek , Moritz Fischer , Tom Rix , Xu Yilun , linux-gpio@vger.kernel.org References: <20260810062105.299808-1-hs@nabladev.com> From: Heiko Schocher In-Reply-To: <20260810062105.299808-1-hs@nabladev.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Last-TLS-Session-Version: TLSv1.3 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260901_215509_923114_EE8032DD X-CRM114-Status: GOOD ( 39.20 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi! On 10.08.26 08:20, Heiko Schocher wrote: > The current driver requests the optional CSI_B and RDWR_B GPIOs but > only configures their initial output state and never changes them > afterwards. As a result, CSI_B and RDWR_B remain inactive or active > throughout the configuration process. > > This may work on systems with a single FPGA where these signals do not > need to be controlled by software, or where the signals are configured > to their active state. But this does not not support systems with > multiple FPGAs sharing a SelectMAP interface. > > On systems with multiple FPGAs sharing the same SelectMAP data bus, > the driver must deassert this signals in probe, and actively control > them during configuration. > > CSI_B (Chip Select, active low) selects the target FPGA. It is asserted > before configuration data is transferred and deasserted afterwards so > that only the intended device responds to bus transactions. > > RDWR_B (Read/Write, active low) controls the transfer direction on the > SelectMAP interface. A low level selects write cycles, while a high > level selects read cycles. During FPGA configuration the driver drives > RDWR_B low before transferring the bitstream and restores it to its > reading (high state) afterwards. > > With that info from the datasheet the driver is now changed to: > > - deassert the CSI_B and RDWR_B pin on probe and store the > optional GPIO descriptors in private driver data. > > - toggle both signals around the configuration data transfer > > This allows multiple FPGAs to safely share a single SelectMAP interface. > > Signed-off-by: Heiko Schocher > --- > > Changes in v4: > - add comments from Xu Yulin > replace wrong gpiod_set_raw_value() with gpiod_set_value() > deassert CSI_B and RDWR_B in probe as in patch version 2 > rework commit message (correct the description what current > driver do on probe), why this is not a problem with one > FPGA, and why it needs a change if you have N FPGAs > sharing the same selectmap Interface (clk and data pins). > > Changes in v3: > - use 0 (deasserted state) and 1 (asserted state) in gpio_set_value() > as commented from Micahl > - rewrite commit message as requested from Xu Yilun > - describe what rdwr_b and csi_b do, and why this change is needed > for more than one FPGA. > - add comment before asserting the signals, why they are asserted > in this order. > > Changes in v2: > - add comments from Michal > - skip check if gpio descriptor variables csi_b/rdwr_b are valid, > as validate_desc() checks this in gpiod_set_value() call. > - initialize the gpio variables csi_b/rdwr_b immediately with > the return value from devm_gpiod_get_optional(), so we can > drop local gpio variable at all > > drivers/fpga/xilinx-selectmap.c | 36 ++++++++++++++++++++++++--------- > 1 file changed, 27 insertions(+), 9 deletions(-) gentle ping. Any updates, comments on this patch? Thanks! bye, Heiko > > diff --git a/drivers/fpga/xilinx-selectmap.c b/drivers/fpga/xilinx-selectmap.c > index d0cbb5fdfe3a..e9b1d15ca054 100644 > --- a/drivers/fpga/xilinx-selectmap.c > +++ b/drivers/fpga/xilinx-selectmap.c > @@ -19,6 +19,8 @@ > struct xilinx_selectmap_conf { > struct xilinx_fpga_core core; > void __iomem *base; > + struct gpio_desc *csi_b; > + struct gpio_desc *rdwr_b; > }; > > #define to_xilinx_selectmap_conf(obj) \ > @@ -30,16 +32,30 @@ static int xilinx_selectmap_write(struct xilinx_fpga_core *core, > struct xilinx_selectmap_conf *conf = to_xilinx_selectmap_conf(core); > size_t i; > > + /* > + * Assert CSI_B and select write mode. > + * > + * UG570 states in note 4 in Figure "Continuous x8 SelectMAP Data > + * Loading", RDWR_B should be asserted before CSI_B to avoid > + * causing an ABORT on the next CCLK. > + * > + * To be sure, set first RDWR_B pin before activate CSI_B > + */ > + gpiod_set_value(conf->rdwr_b, 1); > + gpiod_set_value(conf->csi_b, 1); > + > for (i = 0; i < count; ++i) > writeb(buf[i], conf->base); > > + gpiod_set_value(conf->csi_b, 0); > + gpiod_set_value(conf->rdwr_b, 0); > + > return 0; > } > > static int xilinx_selectmap_probe(struct platform_device *pdev) > { > struct xilinx_selectmap_conf *conf; > - struct gpio_desc *gpio; > void __iomem *base; > > conf = devm_kzalloc(&pdev->dev, sizeof(*conf), GFP_KERNEL); > @@ -55,16 +71,18 @@ static int xilinx_selectmap_probe(struct platform_device *pdev) > "ioremap error\n"); > conf->base = base; > > - /* CSI_B is active low */ > - gpio = devm_gpiod_get_optional(&pdev->dev, "csi", GPIOD_OUT_HIGH); > - if (IS_ERR(gpio)) > - return dev_err_probe(&pdev->dev, PTR_ERR(gpio), > + /* CSI_B is active low, deassert signal */ > + conf->csi_b = devm_gpiod_get_optional(&pdev->dev, "csi", > + GPIOD_OUT_LOW); > + if (IS_ERR(conf->csi_b)) > + return dev_err_probe(&pdev->dev, PTR_ERR(conf->csi_b), > "Failed to get CSI_B gpio\n"); > > - /* RDWR_B is active low */ > - gpio = devm_gpiod_get_optional(&pdev->dev, "rdwr", GPIOD_OUT_HIGH); > - if (IS_ERR(gpio)) > - return dev_err_probe(&pdev->dev, PTR_ERR(gpio), > + /* RDWR_B is active low, deassert signal */ > + conf->rdwr_b = devm_gpiod_get_optional(&pdev->dev, "rdwr", > + GPIOD_OUT_LOW); > + if (IS_ERR(conf->rdwr_b)) > + return dev_err_probe(&pdev->dev, PTR_ERR(conf->rdwr_b), > "Failed to get RDWR_B gpio\n"); > > return xilinx_core_probe(&conf->core); > --- > base-commit: db2ddb87143519e20a95aa36c60b36107b736a58 > -- Nabla Software Engineering HRB 40522 Augsburg Phone: +49 821 45592596 E-Mail: office@nabladev.com Geschäftsführer : Stefano Babic