Re: [PATCH v2 4/4] phy: zynqmp: Add debugfs support

[Sean Anderson <sean.anderson@linux.dev>]

On 6/14/24 01:16, Pandey, Radhey Shyam wrote:
>> -----Original Message-----
>> From: Sean Anderson <sean.anderson@linux.dev>
>> Sent: Thursday, June 13, 2024 8:32 PM
>> To: Pandey, Radhey Shyam <radhey.shyam.pandey@amd.com>; Laurent
>> Pinchart <laurent.pinchart@ideasonboard.com>; linux-
>> phy@lists.infradead.org
>> Cc: Vinod Koul <vkoul@kernel.org>; linux-arm-kernel@lists.infradead.org;
>> linux-kernel@vger.kernel.org; Simek, Michal <michal.simek@amd.com>;
>> Kishon Vijay Abraham I <kishon@kernel.org>
>> Subject: Re: [PATCH v2 4/4] phy: zynqmp: Add debugfs support
>> 
>> On 6/13/24 05:20, Pandey, Radhey Shyam wrote:
>> >> -----Original Message-----
>> >> From: Sean Anderson <sean.anderson@linux.dev>
>> >> Sent: Monday, May 6, 2024 10:31 PM
>> >> To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>; linux-
>> >> phy@lists.infradead.org
>> >> Cc: Vinod Koul <vkoul@kernel.org>; linux-arm-kernel@lists.infradead.org;
>> >> linux-kernel@vger.kernel.org; Michal Simek <michal.simek@amd.com>;
>> >> Kishon Vijay Abraham I <kishon@kernel.org>; Sean Anderson
>> >> <sean.anderson@linux.dev>
>> >> Subject: [PATCH v2 4/4] phy: zynqmp: Add debugfs support
>> >>
>> >> Add support for printing some basic status information to debugfs. This
>> >> is helpful when debugging phy consumers to make sure they are
>> configuring
>> >> the phy appropriately.
>> >>
>> >> Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
>> >> ---
>> >>
>> >> Changes in v2:
>> >> - Use debugfs_create_devm_seqfile
>> >>
>> >>  drivers/phy/xilinx/phy-zynqmp.c | 40
>> >> +++++++++++++++++++++++++++++++++
>> >>  1 file changed, 40 insertions(+)
>> >>
>> >> diff --git a/drivers/phy/xilinx/phy-zynqmp.c b/drivers/phy/xilinx/phy-
>> >> zynqmp.c
>> >> index b86fe2a249a8..2520c75a4a77 100644
>> >> --- a/drivers/phy/xilinx/phy-zynqmp.c
>> >> +++ b/drivers/phy/xilinx/phy-zynqmp.c
>> >> @@ -13,6 +13,7 @@
>> >>   */
>> >>
>> >>  #include <linux/clk.h>
>> >> +#include <linux/debugfs.h>
>> >>  #include <linux/delay.h>
>> >>  #include <linux/io.h>
>> >>  #include <linux/kernel.h>
>> >> @@ -123,6 +124,15 @@
>> >>  #define ICM_PROTOCOL_DP			0x4
>> >>  #define ICM_PROTOCOL_SGMII		0x5
>> >>
>> >> +static const char *const xpsgtr_icm_str[] = {
>> >> +	[ICM_PROTOCOL_PD] = "powered down",
>> >
>> > Protocol saying powered down seems confusing.
>> > Should we say None or None(power down)?
>> 
>> Either works I guess. I'm just matching the define.
> 
> None seems fine - we can respin if there are no objections.
>> 
>> >> +	[ICM_PROTOCOL_PCIE] = "PCIe",
>> >> +	[ICM_PROTOCOL_SATA] = "SATA",
>> >> +	[ICM_PROTOCOL_USB] = "USB",
>> >> +	[ICM_PROTOCOL_DP] = "DisplayPort",
>> >> +	[ICM_PROTOCOL_SGMII] = "SGMII",
>> >> +};
>> >> +
>> >>  /* Test Mode common reset control  parameters */
>> >>  #define TM_CMN_RST			0x10018
>> >>  #define TM_CMN_RST_EN			0x1
>> >> @@ -788,6 +798,34 @@ static struct phy *xpsgtr_xlate(struct device *dev,
>> >>  	return ERR_PTR(-EINVAL);
>> >>  }
>> >>
>> >> +/*
>> >> + * DebugFS
>> >> + */
>> >> +
>> >> +static int xpsgtr_status_read(struct seq_file *seq, void *data)
>> >> +{
>> >> +	struct device *dev = seq->private;
>> >> +	struct xpsgtr_phy *gtr_phy = dev_get_drvdata(dev);
>> >> +	struct clk *clk;
>> >> +	u32 pll_status;
>> >> +
>> >> +	mutex_lock(&gtr_phy->phy->mutex);
>> >
>> > Do we see any need for this lock? This function simply read hw register
>> > /phy members and decodes it.
>> 
>> It's to protect against modifications to gtr_phy->refclk and ->instance.
> 
> Refclock and instance is assigned in xlate which is not protected by any
> Lock.  Also xpsgtr_phy_init () uses a different gtr_mutex. So want
> to understand this phy->mutex need.

Ah, well then we should take this lock in xlate.

--Sean

>> 
>> These are accessed under lock elsewhere; this is not a fast path and I don't
>> want to have to reason about the semantics when using a mutex is definitely
>> correct.
>> 
>> --Sean
>> 
>> >> +	pll_status = xpsgtr_read_phy(gtr_phy, L0_PLL_STATUS_READ_1);
>> >> +	clk = gtr_phy->dev->clk[gtr_phy->refclk];
>> >> +
>> >> +	seq_printf(seq, "Lane:            %u\n", gtr_phy->lane);
>> >> +	seq_printf(seq, "Protocol:        %s\n",
>> >> +		   xpsgtr_icm_str[gtr_phy->protocol]);
>> >> +	seq_printf(seq, "Instance:        %u\n", gtr_phy->instance);
>> >> +	seq_printf(seq, "Reference clock: %u (%pC)\n", gtr_phy->refclk, clk);
>> >> +	seq_printf(seq, "Reference rate:  %lu\n", clk_get_rate(clk));
>> >> +	seq_printf(seq, "PLL locked:      %s\n",
>> >> +		   pll_status & PLL_STATUS_LOCKED ? "yes" : "no");
>> >> +
>> >> +	mutex_unlock(&gtr_phy->phy->mutex);
>> >> +	return 0;
>> >> +}
>> >> +
>> >>  /*
>> >>   * Power Management
>> >>   */
>> >> @@ -937,6 +975,8 @@ static int xpsgtr_probe(struct platform_device
>> *pdev)
>> >>
>> >>  		gtr_phy->phy = phy;
>> >>  		phy_set_drvdata(phy, gtr_phy);
>> >> +		debugfs_create_devm_seqfile(&phy->dev, "status", phy-
>> >> >debugfs,
>> >> +					    xpsgtr_status_read);
>> >>  	}
>> >>
>> >>  	/* Register the PHY provider. */
>> >> --
>> >> 2.35.1.1320.gc452695387.dirty
>> >
>