linux-kernel - [PATCH] spi: bcm2835: Set controller max_speed

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Date:   Thu, 7 Jan 2021 16:48:25 +0000
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     <broonie@...nel.org>, <nsaenzjulienne@...e.de>,
        <f.fainelli@...il.com>, <rjui@...adcom.com>,
        <sbranden@...adcom.com>
CC:     <bcm-kernel-feedback-list@...adcom.com>,
        <linux-spi@...r.kernel.org>,
        <linux-rpi-kernel@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <patches@...nsource.cirrus.com>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>
Subject: [PATCH] spi: bcm2835: Set controller max_speed_hz

Set the struct spi_controller max_speed_hz. This is based on the
reported source clock frequency during probe. The maximum bus clock
is half the source clock (as per the code in bcm2835_spi_transfer_one).

If the controller max_speed_hz is not set, the spi core will limit all
transfers to 0 Hz so only the minimum possible bus frequency would be used.

Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
---
 drivers/spi/spi-bcm2835.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index 197485f2c2b2..8e161f4f7766 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -1307,6 +1307,8 @@ static int bcm2835_spi_probe(struct platform_device *pdev)
 		return dev_err_probe(&pdev->dev, PTR_ERR(bs->clk),
 				     "could not get clk\n");
 
+	ctlr->max_speed_hz = clk_get_rate(bs->clk) / 2;
+
 	bs->irq = platform_get_irq(pdev, 0);
 	if (bs->irq <= 0)
 		return bs->irq ? bs->irq : -ENODEV;
-- 
2.20.1