| Message ID | 1532358123-23485-3-git-send-email-manish.narani@xilinx.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iio: adc: xilinx: XADC driver Enhancements and bug fixes | expand |
On Mon, 23 Jul 2018 20:32:01 +0530 Manish Narani <manish.narani@xilinx.com> wrote: > This patch limits the xadc pcap clock frequency value to be less than > 200MHz. This fixes the issue when zynq is booted at higher frequency > values, pcap crosses the maximum limit of 200MHz(Fmax) as it is derived > from IOPLL. > If this limit is crossed it is required to alter the WEDGE and REDGE > bits of XADC_CFG register to make timings better in the interface. So to > avoid alteration of these bits every time, the pcap value should not > cross the Fmax limit. > > Signed-off-by: Manish Narani <manish.narani@xilinx.com> Applied, to the togreg branch of iio.git. If you want this backported to stable, then request it once this patch is upstream. It may be sometime given we've probably just missed the coming merge window. If you do need it faster then let me know and I'll look at moving it over to the branch of fixes during the RC phases. Jonathan > --- > drivers/iio/adc/xilinx-xadc-core.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c > index 23395fc..0dd306d 100644 > --- a/drivers/iio/adc/xilinx-xadc-core.c > +++ b/drivers/iio/adc/xilinx-xadc-core.c > @@ -322,6 +322,7 @@ static irqreturn_t xadc_zynq_interrupt_handler(int irq, void *devid) > > #define XADC_ZYNQ_TCK_RATE_MAX 50000000 > #define XADC_ZYNQ_IGAP_DEFAULT 20 > +#define XADC_ZYNQ_PCAP_RATE_MAX 200000000 > > static int xadc_zynq_setup(struct platform_device *pdev, > struct iio_dev *indio_dev, int irq) > @@ -332,6 +333,7 @@ static int xadc_zynq_setup(struct platform_device *pdev, > unsigned int div; > unsigned int igap; > unsigned int tck_rate; > + int ret; > > /* TODO: Figure out how to make igap and tck_rate configurable */ > igap = XADC_ZYNQ_IGAP_DEFAULT; > @@ -343,6 +345,13 @@ static int xadc_zynq_setup(struct platform_device *pdev, > if (!pcap_rate) > return -EINVAL; > > + if (pcap_rate > XADC_ZYNQ_PCAP_RATE_MAX) { > + ret = clk_set_rate(xadc->clk, > + (unsigned long)XADC_ZYNQ_PCAP_RATE_MAX); > + if (ret) > + return ret; > + } > + > if (tck_rate > pcap_rate / 2) { > div = 2; > } else { > @@ -368,6 +377,12 @@ static int xadc_zynq_setup(struct platform_device *pdev, > XADC_ZYNQ_CFG_REDGE | XADC_ZYNQ_CFG_WEDGE | > tck_div | XADC_ZYNQ_CFG_IGAP(igap)); > > + if (pcap_rate > XADC_ZYNQ_PCAP_RATE_MAX) { > + ret = clk_set_rate(xadc->clk, pcap_rate); > + if (ret) > + return ret; > + } > + > return 0; > } >
Hi Jonathan, > -----Original Message----- > From: Jonathan Cameron [mailto:jic23@kernel.org] > Sent: Sunday, July 29, 2018 5:21 PM > To: Manish Narani <MNARANI@xilinx.com> > Cc: Sai Krishna Potthuri <lakshmis@xilinx.com>; Michal Simek > <michals@xilinx.com>; pmeerw@pmeerw.net; lars@metafoo.de; > knaack.h@gmx.de; Anirudha Sarangi <anirudh@xilinx.com>; Srinivas Goud > <sgoud@xilinx.com>; linux-kernel@vger.kernel.org; linux-arm- > kernel@lists.infradead.org; linux-iio@vger.kernel.org > Subject: Re: [PATCH v2 2/4] iio: adc: xilinx: limit pcap clock frequency value > > On Mon, 23 Jul 2018 20:32:01 +0530 > Manish Narani <manish.narani@xilinx.com> wrote: > > > This patch limits the xadc pcap clock frequency value to be less than > > 200MHz. This fixes the issue when zynq is booted at higher frequency > > values, pcap crosses the maximum limit of 200MHz(Fmax) as it is > > derived from IOPLL. > > If this limit is crossed it is required to alter the WEDGE and REDGE > > bits of XADC_CFG register to make timings better in the interface. So > > to avoid alteration of these bits every time, the pcap value should > > not cross the Fmax limit. > > > > Signed-off-by: Manish Narani <manish.narani@xilinx.com> > > Applied, to the togreg branch of iio.git. If you want this backported to stable, > then request it once this patch is upstream. It may be sometime given we've > probably just missed the coming merge window. > > If you do need it faster then let me know and I'll look at moving it over to the > branch of fixes during the RC phases. Thanks for getting this applied. There is no concern for this to be in the stable ASAP. I can wait. Thanks & Regards, Manish Narani
diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c index 23395fc..0dd306d 100644 --- a/drivers/iio/adc/xilinx-xadc-core.c +++ b/drivers/iio/adc/xilinx-xadc-core.c @@ -322,6 +322,7 @@ static irqreturn_t xadc_zynq_interrupt_handler(int irq, void *devid) #define XADC_ZYNQ_TCK_RATE_MAX 50000000 #define XADC_ZYNQ_IGAP_DEFAULT 20 +#define XADC_ZYNQ_PCAP_RATE_MAX 200000000 static int xadc_zynq_setup(struct platform_device *pdev, struct iio_dev *indio_dev, int irq) @@ -332,6 +333,7 @@ static int xadc_zynq_setup(struct platform_device *pdev, unsigned int div; unsigned int igap; unsigned int tck_rate; + int ret; /* TODO: Figure out how to make igap and tck_rate configurable */ igap = XADC_ZYNQ_IGAP_DEFAULT; @@ -343,6 +345,13 @@ static int xadc_zynq_setup(struct platform_device *pdev, if (!pcap_rate) return -EINVAL; + if (pcap_rate > XADC_ZYNQ_PCAP_RATE_MAX) { + ret = clk_set_rate(xadc->clk, + (unsigned long)XADC_ZYNQ_PCAP_RATE_MAX); + if (ret) + return ret; + } + if (tck_rate > pcap_rate / 2) { div = 2; } else { @@ -368,6 +377,12 @@ static int xadc_zynq_setup(struct platform_device *pdev, XADC_ZYNQ_CFG_REDGE | XADC_ZYNQ_CFG_WEDGE | tck_div | XADC_ZYNQ_CFG_IGAP(igap)); + if (pcap_rate > XADC_ZYNQ_PCAP_RATE_MAX) { + ret = clk_set_rate(xadc->clk, pcap_rate); + if (ret) + return ret; + } + return 0; }
This patch limits the xadc pcap clock frequency value to be less than 200MHz. This fixes the issue when zynq is booted at higher frequency values, pcap crosses the maximum limit of 200MHz(Fmax) as it is derived from IOPLL. If this limit is crossed it is required to alter the WEDGE and REDGE bits of XADC_CFG register to make timings better in the interface. So to avoid alteration of these bits every time, the pcap value should not cross the Fmax limit. Signed-off-by: Manish Narani <manish.narani@xilinx.com> --- drivers/iio/adc/xilinx-xadc-core.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)