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Date: Thu, 12 Mar 2020 21:52:38 +0000
From: Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
CC: Mauro Carvalho Chehab <mchehab@...nel.org>,
Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Sakari Ailus <sakari.ailus@...ux.intel.com>,
NXP Linux Team <linux-imx@....com>,
Magnus Damm <magnus.damm@...il.com>,
Ezequiel Garcia <ezequiel@...labora.com>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
Fabio Estevam <festevam@...il.com>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Media Mailing List <linux-media@...r.kernel.org>
Subject: RE: [PATCH v2 2/3] media: i2c: ov5645: Switch to assigned-clock-rates
Hi Geert,
Thank you for the quick review.
> -----Original Message-----
> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: 12 March 2020 21:42
> To: Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
> Cc: Mauro Carvalho Chehab <mchehab@...nel.org>; Shawn Guo
> <shawnguo@...nel.org>; Sascha Hauer <s.hauer@...gutronix.de>;
> Pengutronix Kernel Team <kernel@...gutronix.de>; Rob Herring
> <robh+dt@...nel.org>; Mark Rutland <mark.rutland@....com>; Sakari
> Ailus <sakari.ailus@...ux.intel.com>; NXP Linux Team <linux-imx@....com>;
> Magnus Damm <magnus.damm@...il.com>; Ezequiel Garcia
> <ezequiel@...labora.com>; open list:OPEN FIRMWARE AND FLATTENED
> DEVICE TREE BINDINGS <devicetree@...r.kernel.org>; Linux Kernel Mailing
> List <linux-kernel@...r.kernel.org>; Linux-Renesas <linux-renesas-
> soc@...r.kernel.org>; Fabio Estevam <festevam@...il.com>; Linux ARM
> <linux-arm-kernel@...ts.infradead.org>; Linux Media Mailing List <linux-
> media@...r.kernel.org>
> Subject: Re: [PATCH v2 2/3] media: i2c: ov5645: Switch to assigned-clock-
> rates
>
> Hi Prabhakar,
>
> On Thu, Mar 12, 2020 at 10:13 PM Lad Prabhakar <prabhakar.mahadev-
> lad.rj@...renesas.com> wrote:
> > This patch switches to assigned-clock-rates for specifying the clock rate.
> > The clk-conf.c internally handles setting the clock rate when
> > assigned-clock-rates is passed.
> >
> > The driver now sets the clock frequency only if the deprecated
> > property clock-frequency is defined instead assigned-clock-rates, this
> > is to avoid breakage with existing DT binaries.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-
> lad.rj@...renesas.com>
>
> Thanks for your patch!
>
> > --- a/drivers/media/i2c/ov5645.c
> > +++ b/drivers/media/i2c/ov5645.c
> > @@ -1055,6 +1055,7 @@ static int ov5645_probe(struct i2c_client *client)
> > struct device_node *endpoint;
> > struct ov5645 *ov5645;
> > u8 chip_id_high, chip_id_low;
> > + bool set_clk = false;
> > unsigned int i;
> > u32 xclk_freq;
> > int ret;
> > @@ -1094,10 +1095,17 @@ static int ov5645_probe(struct i2c_client
> *client)
> > return PTR_ERR(ov5645->xclk);
> > }
> >
> > - ret = of_property_read_u32(dev->of_node, "clock-frequency",
> &xclk_freq);
> > + ret = of_property_read_u32(dev->of_node, "assigned-clock-rates",
> > + &xclk_freq);
> > if (ret) {
>
> I think you can just leave out the above check...
>
> > - dev_err(dev, "could not get xclk frequency\n");
> > - return ret;
> > + /* check if deprecated property clock-frequency is defined */
> > + ret = of_property_read_u32(dev->of_node, "clock-frequency",
> > + &xclk_freq);
> > + if (ret) {
>
> ... and ignore the absence of the deprecated property.
>
> > + dev_err(dev, "could not get xclk frequency\n");
> > + return ret;
> > + }
> > + set_clk = true;
>
> I.e. just
>
> /* check if deprecated property clock-frequency is defined */
> xclk_freq = 0;
> of_property_read_u32(dev->of_node, "clock-frequency", &xclk_freq);
> if (xclk_freq) {
> ret = clk_set_rate(ov5645->xclk, xclk_freq);
> if (ret) {
> dev_err(dev, "could not set xclk frequency\n");
> return ret;
> }
> } else {
> xclk_freq = clk_get_rate(ov5645->xclk, xclk_freq);
> }
>
I did think about it initially, but realized the clk_get_rate may vary platform to platform
for example in G2E clk_get_rate() returns a frequency of 24242424 with
assigned-clock-rates set to 24000000 and probe would fail due to a check for
external clock must be 24MHz, with 1% tolerance.
Cheers,
--Prabhakar
> > }
> >
> > /* external clock must be 24MHz, allow 1% tolerance */ @@
> > -1107,10 +1115,12 @@ static int ov5645_probe(struct i2c_client *client)
> > return -EINVAL;
> > }
> >
> > - ret = clk_set_rate(ov5645->xclk, xclk_freq);
> > - if (ret) {
> > - dev_err(dev, "could not set xclk frequency\n");
> > - return ret;
> > + if (set_clk) {
> > + ret = clk_set_rate(ov5645->xclk, xclk_freq);
> > + if (ret) {
> > + dev_err(dev, "could not set xclk frequency\n");
> > + return ret;
> > + }
>
> > }
> >
> > for (i = 0; i < OV5645_NUM_SUPPLIES; i++)
> > --
> > 2.7.4
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
>
>
> --
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-
> m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
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