Messages in this thread | | | Date | Mon, 13 Jun 2022 07:53:25 +0200 | From | Sam Ravnborg <> | Subject | Re: [LINUX PATCH 2/2] drm: xlnx: dsi: driver for Xilinx DSI Tx subsystem |
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Hi Laurent,
> [snip] > > > > +static inline void xlnx_dsi_writel(void __iomem *base, int offset, u32 val) > > > +{ > > > + writel(val, base + offset); > > > +} > > > + > > > +static inline u32 xlnx_dsi_readl(void __iomem *base, int offset) > > > +{ > > > + return readl(base + offset); > > > +} > > > > When I see implementations like this I wonder if a regmap would be > > beneficial? > > regmap often seems overkill to me when the driver only needs plain > 32-bit mmio read/write, given the overhead it adds at runtime. Is it > just me ?
There are several points that speaks for using regmap: - The interface is well known - It has nice helpers - like update_bits - No need for own wrappers, that sometimes are made in creative ways (not the case here) - There is a possibility to add some run-time checks so one can catch attempt to write outside the register window, write to read-only registers etc.
On top of this - it is simple to configure:
static const struct regmap_config regmap_config = { .reg_bits = 32, .val_bits = 32, .reg_stride = 4, };
From the probe function:
priv->regs = devm_platform_get_and_ioremap_resource(pdev, 0, &res); if (IS_ERR(priv->regs)) return dev_err_probe(dev, PTR_ERR(priv->regs), "Failed to get memory resource\n");
regmap_cfg = regmap_config; regmap_cfg.max_register = res->end - res->start; priv->regmap = devm_regmap_init_mmio(dev, priv->regs, ®map_cfg); if (IS_ERR(priv->regmap)) return dev_err_probe(dev, PTR_ERR(priv->regmap), "Failed to init regmap\n");
The one point that brought me over was the well known interface. But using wrappers works too.
Sam
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