Re: [PATCH v2] i3c: master: cdns: add data hold delay support

[Przemyslaw Gaj <pgaj@cadence.com>]

The 11/15/2019 12:05, Boris Brezillon wrote:
> 
> On Fri, 15 Nov 2019 07:23:26 +0100
> Przemyslaw Gaj <pgaj@cadence.com> wrote:
> 
> > This patch adds support for THD_DEL (Data Hold Delay) to Cadence
> > I3C master constoller driver.
> > 
> > As per MIPI I3C Specification 1.0, Table 75 (page 142) defines
> > non-zero minimal tHD_PP timing on master output (Fig 65). This
> > setting allows to meet this timing on master's soc outputs,
> > regardless of PCB balancing.
> > 
> > Signed-off-by: Przemyslaw Gaj <pgaj@cadence.com>
> > 
> > ---
> > 
> > Main changes between v1 and v2:
> > - Add device-specific data which holds the thd_del value
> > - Remove device tree property
> > ---
> >  drivers/i3c/master/i3c-master-cdns.c | 37 +++++++++++++++++++++++++++++++-----
> >  1 file changed, 32 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/i3c/master/i3c-master-cdns.c b/drivers/i3c/master/i3c-master-cdns.c
> > index 10db0bf0655a..3531396f04fd 100644
> > --- a/drivers/i3c/master/i3c-master-cdns.c
> > +++ b/drivers/i3c/master/i3c-master-cdns.c
> > @@ -22,6 +22,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/spinlock.h>
> >  #include <linux/workqueue.h>
> > +#include <linux/of_device.h>
> >  
> >  #define DEV_ID				0x0
> >  #define DEV_ID_I3C_MASTER		0x5034
> > @@ -60,6 +61,7 @@
> >  #define CTRL_HALT_EN			BIT(30)
> >  #define CTRL_MCS			BIT(29)
> >  #define CTRL_MCS_EN			BIT(28)
> > +#define CTRL_THD_DEL(x)			(((x) << 24) & GENMASK(25, 24))
> 
> DEL is a bit ambiguous, how about _DELAY().
>

Yes, I can change it. I took this name directly from register map. As
rest of the names :-)
 
> >  #define CTRL_HJ_DISEC			BIT(8)
> >  #define CTRL_MST_ACK			BIT(7)
> >  #define CTRL_HJ_ACK			BIT(6)
> > @@ -388,6 +390,10 @@ struct cdns_i3c_xfer {
> >  	struct cdns_i3c_cmd cmds[0];
> >  };
> >  
> > +struct cdns_i3c_data {
> > +	u8 thd_del;
> 
> Same here, thd_delay. BTW, is the clk driving the I3C master clk
> expected to be fixed? If not, I'd suggest expressing this delay is
> seconds (nano or micro depending on the precision you need) so the
> driver can calculate the proper thd_delay value based on
> clk_get_rate(master->sysclk).
> 

Ok. I'll think about that. It is possible to change frequency so maybe
it's good to calculate that instead of hardcoding that value.

> > +};
> > +
> >  struct cdns_i3c_master {
> >  	struct work_struct hj_work;
> >  	struct i3c_master_controller base;
> > @@ -408,6 +414,7 @@ struct cdns_i3c_master {
> >  	struct clk *pclk;
> >  	struct cdns_i3c_master_caps caps;
> >  	unsigned long i3c_scl_lim;
> > +	const struct cdns_i3c_data *devdata;
> >  };
> >  
> >  static inline struct cdns_i3c_master *
> > @@ -1264,6 +1271,15 @@ static int cdns_i3c_master_bus_init(struct i3c_master_controller *m)
> >  	 * We will issue ENTDAA afterwards from the threaded IRQ handler.
> >  	 */
> >  	ctrl |= CTRL_HJ_ACK | CTRL_HJ_DISEC | CTRL_HALT_EN | CTRL_MCS_EN;
> > +
> > +	/*
> > +	 * Configure data hold delay based on device-specific data.
> > +	 *
> > +	 * MIPI I3C Specification 1.0 defines non-zero minimal tHD_PP timing on
> > +	 * master output. This setting allows to meet this timing on master's
> > +	 * SoC outputs, regardless of PCB balancing.
> > +	 */
> > +	ctrl |= CTRL_THD_DEL(master->devdata->thd_del);
> >  	writel(ctrl, master->regs + CTRL);
> >  
> >  	cdns_i3c_master_enable(master);
> > @@ -1521,17 +1537,33 @@ static void cdns_i3c_master_hj(struct work_struct *work)
> >  	i3c_master_do_daa(&master->base);
> >  }
> >  
> > +static struct cdns_i3c_data cdns_i3c_devdata = {
> > +	.thd_del = 0x3,
> > +};
> > +
> > +static const struct of_device_id cdns_i3c_master_of_ids[] = {
> > +	{ .compatible = "cdns,i3c-master", .data = &cdns_i3c_devdata },
> > +	{ /* sentinel */ },
> > +};
> > +
> >  static int cdns_i3c_master_probe(struct platform_device *pdev)
> >  {
> >  	struct cdns_i3c_master *master;
> > +	const struct of_device_id *of_id = of_match_device(
> > +		of_match_ptr(cdns_i3c_master_of_ids), &pdev->dev);
> 
> The of_match_ptr() is not needed since cdns_i3c_master_of_ids is always
> defined.
> 
> 
> >  	struct resource *res;
> >  	int ret, irq;
> >  	u32 val;
> >  
> > +	if (!of_id)
> > +		return -ENODEV;
> > +
> 
> Not sure ENODEV is the right error code here. If of_id == NULL that
> means cdns_i3c_master_of_ids[] is not filled correctly, so I'd suggest
> returning EINVAL.
> 
> >  	master = devm_kzalloc(&pdev->dev, sizeof(*master), GFP_KERNEL);
> >  	if (!master)
> >  		return -ENOMEM;
> >  
> > +	master->devdata = of_id->data;
> 
> If you do:
> 
> 	master->devdata = of_device_get_match_data(&pdev->dev);
> 	if (!master->devdata)
> 		return -EINVAL;
> 
> You can get rid of of_id (and the associate assignment/test).
> 

Ok. Thank you.

> > +
> >  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >  	master->regs = devm_ioremap_resource(&pdev->dev, res);
> >  	if (IS_ERR(master->regs))
> > @@ -1631,11 +1663,6 @@ static int cdns_i3c_master_remove(struct platform_device *pdev)
> >  	return 0;
> >  }
> >  
> > -static const struct of_device_id cdns_i3c_master_of_ids[] = {
> > -	{ .compatible = "cdns,i3c-master" },
> > -	{ /* sentinel */ },
> > -};
> > -
> >  static struct platform_driver cdns_i3c_master = {
> >  	.probe = cdns_i3c_master_probe,
> >  	.remove = cdns_i3c_master_remove,
> 

-- 
-- 
Przemyslaw Gaj

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