Re: [PATCH v7 4/8] Bluetooth: btqca: Redefine qca_uart_setup() to generic function.

[Matthias Kaehlcke <mka@chromium.org>]

Hi Balakrishna,

On Wed, Jun 20, 2018 at 04:23:25PM +0530, Balakrishna Godavarthi wrote:
> Hi Matthias,
> 
> On 2018-06-20 01:33, Matthias Kaehlcke wrote:
> > On Tue, Jun 19, 2018 at 12:39:07PM +0530, Balakrishna Godavarthi wrote:
> > > Hi Matthias,
> > > 
> > > Please find my comments inline.
> > > 
> > > On 2018-06-19 02:49, Matthias Kaehlcke wrote:
> > > > On Sat, Jun 16, 2018 at 11:57:14AM +0530, Balakrishna Godavarthi wrote:
> > > >
> > > > > @@ -337,19 +337,20 @@ int qca_uart_setup(struct hci_dev *hdev,
> > > > > uint8_t baudrate)
> > > > >
> > > > >  	config.user_baud_rate = baudrate;
> > > > >
> > > > > -	/* Get QCA version information */
> > > > > -	err = qca_read_soc_version(hdev, &rome_ver);
> > > > > -	if (err < 0 || rome_ver == 0) {
> > > > > -		bt_dev_err(hdev, "QCA Failed to get version %d", err);
> > > > > -		return err;
> > > > > +	if (!soc_ver) {
> > > > > +		/* Get QCA version information */
> > > > > +		err = qca_read_soc_version(hdev, &soc_ver);
> > > > > +		if (err < 0 || soc_ver == 0) {
> > > > > +			bt_dev_err(hdev, "QCA Failed to get version %d", err);
> > > > > +			return err;
> > > > > +		}
> > > > > +		bt_dev_info(hdev, "QCA controller version 0x%08x", soc_ver);
> > > > >  	}
> > > >
> > > > Why is this needed? A caller that passes in soc_ver = 0 could just
> > > > call qca_read_soc_version() themselves.
> > > [Bala]: hci_qca support two chip one ROME (already up-streamed) and
> > > other
> > > wcn3990.
> > >         there setup sequence differs.
> > > 
> > >         wcn3900:
> > >         1. set baudrate to 115200
> > >         2. read soc version
> > >         3. set baudarte to 3.2Mbps
> > >         4. download firmware. (calls qca_uart_setup)
> > > 
> > >        ROME:
> > >        1. set baudrate to 3.0 mbps
> > >        2. calls qca_uart_setup to read soc version and download
> > > firmware.
> > > 
> > >       so to make use of existing function qca_setup_uart(). passing
> > > soc_ver
> > > as argument.
> > >       if soc_ver is zero, then read soc version (i.e. for ROME chip).
> > > 
> > >       Pls let me know, if you have any queries.
> > 
> > I don't really understand this argumentation. Let's look at the code
> > at the end of this series, where both Rome and wcn3900 are supported:
> > 
> > https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1045608/6/drivers/bluetooth/hci_qca.c#1059
> > 
> > The version could be read (for Rome only) after setting the operating
> > speed:
> 
> [Bala]: yes we can read SoC version after setting operating baud rate. an
> advice from SoC vendor that, read SoC version before setting operating
> speed.
>         one advantage from reading SoC version before setting operating
> baudrate,it will helps us to understand whether the soc is responding to any
> commands in default baud rate
>         before setting operating speed.

Is the recommendation for Rome or wcn3990? I was referring to Rome and
the current code sets the operating speed and then reads the SoC
version (inside qca_uart_setup())

> > https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1045608/6/drivers/bluetooth/hci_qca.c#1111
> > 
> > I concede that having two "if (qcadev->btsoc_type == XYZ)" branches in
> > qca_setup() is kinda ugly, but I think it's still better than the
> > conditional call of qca_read_soc_version() in qca_uart_setup().
> 
> [Bala]: we require an if-else block  for soc type.As wcn3900 support
> hardware flow control where as ROME is not supporting hardware flow control.

Since you mention if-else and flow control I'm not sure if you
understood correctly what I suggested. My suggestion is to add
something like this:

if (qcadev->btsoc_type == QCA_ROME) {
	ret = qca_read_soc_version(hdev, &soc_ver);
	if (ret < 0 || soc_ver == 0) {
	   	// Note mka@: we might want to skip this log,
		// qca_read_soc_version() already logs in all error paths
		bt_dev_err(hdev, "Failed to get version %d", ret);
		return ret;
	}
}

right here:

https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1045608/6/drivers/bluetooth/hci_qca.c#1111

which is functionally equivalent to the current code.

You could even do the error check in the common code (just checking
for 'soc_ver == 0', assuming that qca_read_soc_version() doesn't set
it to something different in case of error).

Anyway, I won't insist if you prefer it as is and Marcel is ok with it.