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w1: mxc_w1: Add warning for base frequency calculation

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Base frequency should be as close as possible to 1 MHz. This patch
adds warnings when clock is unreliable, according to i.MX datasheet.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alexander Shiyan 2013-11-29 15:39:29 +04:00 committed by Greg Kroah-Hartman
parent a082263725
commit 71531f55a8
1 changed files with 12 additions and 2 deletions
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14
drivers/w1/masters/mxc_w1.c
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@ -105,6 +105,7 @@ static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit)
static int mxc_w1_probe(struct platform_device *pdev)
{
struct mxc_w1_device *mdev;
unsigned long clkrate;
struct resource *res;
unsigned int clkdiv;
int err = 0;
@ -118,7 +119,16 @@ static int mxc_w1_probe(struct platform_device *pdev)
if (IS_ERR(mdev->clk))
return PTR_ERR(mdev->clk);
clkdiv = (clk_get_rate(mdev->clk) / 1000000) - 1;
clkrate = clk_get_rate(mdev->clk);
if (clkrate < 10000000)
dev_warn(&pdev->dev,
"Low clock frequency causes improper function\n");
clkdiv = DIV_ROUND_CLOSEST(clkrate, 1000000);
clkrate /= clkdiv;
if ((clkrate < 980000) || (clkrate > 1020000))
dev_warn(&pdev->dev,
"Incorrect time base frequency %lu Hz\n", clkrate);
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
mdev->regs = devm_ioremap_resource(&pdev->dev, res);
@ -126,7 +136,7 @@ static int mxc_w1_probe(struct platform_device *pdev)
return PTR_ERR(mdev->regs);
clk_prepare_enable(mdev->clk);
__raw_writeb(clkdiv, mdev->regs + MXC_W1_TIME_DIVIDER);
__raw_writeb(clkdiv - 1, mdev->regs + MXC_W1_TIME_DIVIDER);
mdev->bus_master.data = mdev;
mdev->bus_master.reset_bus = mxc_w1_ds2_reset_bus;