> -----Original Message----- > From: Chen Guangyu-B42378 > Sent: Monday, August 19, 2013 8:38 AM > To: Bhushan Bharat-R65777 > Cc: broo...@kernel.org; l...@metafoo.de; p.za...@pengutronix.de; > s.ha...@pengutronix.de; mark.rutl...@arm.com; devicet...@vger.kernel.org; > alsa- > de...@alsa-project.org; swar...@wwwdotorg.org; feste...@gmail.com; > ti...@tabi.org; rob.herr...@calxeda.com; tomasz.f...@gmail.com; > shawn....@linaro.org; linuxppc-dev@lists.ozlabs.org > Subject: Re: [PATCH v6 1/2] ASoC: fsl: Add S/PDIF CPU DAI driver > > Hi Bhushan, > > Thank you for the comments :) > I'll fix some in v7. > > Here is my some replies to you. > > On Sat, Aug 17, 2013 at 02:24:19AM +0800, Bhushan Bharat-R65777 wrote: > > > This patch add S/PDIF controller driver for Freescale SoC. > > > > Please give some more description of the driver? > > I've referred some ASoC drivers, all of them seem to be brief as mine. > So I'm not sure what else information I should provide here. It's already > kinda > okay to me.
Other does not have description does not mean we also should not add description here. Please describe in few lines about this driver and devices it handles? > > > > > +struct spdif_mixer_control { > > > + /* buffer ptrs for writer */ > > > + u32 upos; > > > + u32 qpos; > > > > They does not look like pointer? > > They are more like offsets to get the correspond pointer. > But I'll change the confusing comments. > > > > > +/* U/Q Channel receive register full */ static void > > > +spdif_irq_uqrx_full(struct fsl_spdif_priv *spdif_priv, char name) { > > > + struct spdif_mixer_control *ctrl = &spdif_priv->fsl_spdif_control; > > > + struct regmap *regmap = spdif_priv->regmap; > > > + struct platform_device *pdev = spdif_priv->pdev; > > > + u32 *pos, size, val, reg; > > > + > > > + switch (name) { > > > + case 'U': > > > + pos = &ctrl->upos; > > > + size = SPDIF_UBITS_SIZE; > > > + reg = REG_SPDIF_SRU; > > > + break; > > > + case 'Q': > > > + pos = &ctrl->qpos; > > > + size = SPDIF_QSUB_SIZE; > > > + reg = REG_SPDIF_SRQ; > > > + break; > > > + default: > > > + return; > > > > Should return error. > > IMHO, this should be fine. It's a void type function and being used in the > isr(). The params 'name' is totally controlled by driver itself, so basically > we > don't need to worry about the default path. Silently returning on potential error is bad. At least add a printk/BUGON or something similar which points that some unexpected parameter is passed. > > > > + if (*pos >= size * 2) { > > > + *pos = 0; > > > + } else if (unlikely((*pos % size) + 3 > size)) { > > > + dev_err(&pdev->dev, "User bit receivce buffer overflow\n"); > > > + return; > > > > Should return error. > > Ditto, it's being used in isr(), we don't need to detect the return value, > just > use dev_err() to warn users and let the driver clear the irq. Same as above > > > > > +/* U/Q Channel framing error */ > > > +static void spdif_irq_uq_err(struct fsl_spdif_priv *spdif_priv) { > > > + struct spdif_mixer_control *ctrl = &spdif_priv->fsl_spdif_control; > > > + struct regmap *regmap = spdif_priv->regmap; > > > + struct platform_device *pdev = spdif_priv->pdev; > > > + u32 val; > > > + > > > + dev_dbg(&pdev->dev, "isr: U/Q Channel framing error\n"); > > > + > > > + /* read U/Q data and do buffer reset */ > > > + regmap_read(regmap, REG_SPDIF_SRU, &val); > > > + regmap_read(regmap, REG_SPDIF_SRQ, &val); > > > > Above prints says read u/q data and buffer reset, what is buffer reset? Is > that read on clear? > > That's the behavior needed by IP, according to the reference manual: > "U Channel receive register full, can't be cleared with reg. IntClear. > To clear it, read from U Rx reg." and "Q Channel receive register full, can't > be > cleared with reg. IntClear. To clear it, read from Q Rx reg." Then please add this behavior in comment. > > > > > +static void spdif_softreset(struct fsl_spdif_priv *spdif_priv) { > > > + struct regmap *regmap = spdif_priv->regmap; > > > + u32 val, cycle = 1000; > > > + > > > + regmap_write(regmap, REG_SPDIF_SCR, SCR_SOFT_RESET); > > > + regcache_sync(regmap); > > > + > > > + /* RESET bit would be cleared after finishing its reset procedure */ > > > + do { > > > + regmap_read(regmap, REG_SPDIF_SCR, &val); > > > + } while ((val & SCR_SOFT_RESET) && cycle--); > > > > What if reset is not cleared and timeout happen? > > We here suppose the reset bit would be cleared -- "The software reset will > last > 8 cycles." from RM, so if this happened to be a failure, the whole IP module > won't be normally working as well. Also add a comment describing this against why cycle = 1000 is selected. > > Well, but I don't mind to put here an extra failed return to make it clear. > > > > > +static u8 reverse_bits(u8 input) > > > +{ > > > + u8 tmp = input; > > > + > > > + tmp = ((tmp & 0b10101010) >> 1) | ((tmp << 1) & 0b10101010); > > > + tmp = ((tmp & 0b11001100) >> 2) | ((tmp << 2) & 0b11001100); > > > + tmp = ((tmp & 0b11110000) >> 4) | ((tmp << 4) & 0b11110000); > > > > What is this logic, can the hardcoding be removed and some description on > above calculation? > > This was provided by Philipp Zabel in his review at patch v3. > It's pretty clear to me that it just reverses the bits for u8. This is not obvious. Why not use bitrev8() ? > I don't think this logic has any problem and the mask here doesn't look like > any > hardcode to me. > > > > > +static bool fsl_spdif_volatile_reg(struct device *dev, unsigned int reg) > > > +{ > > > + /* Sync all registers after reset */ > > > > Where us sync :) ? > > The "return true" would do that. For volatile registers, if no "return true" > here, the whole regmap would use the value in cache, while for some bits > we need to trace its true value from the physical registers not from cache. Where will be device registers cached? Do not we program them to be non-cacheable in core? -Bharat > > > Best regards, > Nicolin Chen _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev